Monday, 31 October 2016

lens - Are micro four thirds lenses fully interchangeable between brands?


I'm thinking about switching from DSLR to Micro 4/3, and I've found several brands of cameras and lenses, and I want to know if I buy a camera from a specific brand, will I be stuck to that brand lenses? Or I can mix different camera/lens brands?


My main question is: Will the lenses be fully operational if I mix brands, or I won't have features like AF available?



Answer



You can mix & match lenses from different manufacturers, with just a few caveats.




  • Autofocus will work for all MFT lenses on all MFT bodies (that I am aware of).

  • Image stabilization: Olympus does in-body image stabilization (IBIS), whereas Panasonic bodies prior the GX7 and GX8 placed the image stabilization in the lens. This means that Olympus lenses on older Panasonic bodies will not have any image stabilization; conversely, some combinations of Olympus bodies with Panasonic lenses with hardware image stabilization switches will allow you to choose from either IS (either Olympus IBIS or Panasonic lens IS).

  • Lens correction: in-camera lens correction is not guaranteed to work for all combinations. This is usually a low-impact issue: post-processing with software such as Lightroom can allow you to perform lens corrections.




†: User vclaw helpfully reminded me that the Panasonic Lumix GX7 and GX8 cameras have in-body image stabilization.


Saturday, 29 October 2016

Measuring SNR of a DSLR from raw image


How can I calculate signal to noise ratio of a DSLR, using raw images?

Is it simply whole counts minus dark counts over dark counts?




lens - Upgrade from EF-S 15-85 IS


I currently own a Canon 60D, and I am perfectly happy with the camera. It is going to be years until I move to a better (most likely full-frame) body.


My main, walk-around lens is the 15-85. I am also very happy with this lens, although I also know its shortcomings, like the variable aperture (3.5-5.6).


But this morning, as a "what if" exercise, I started thinking about upgrading this lens.



Since my 60D is a crop sensor body, the closest and cheapest upgrade I can do is the 17-55 EF-S USM IS. It has a constant aperture of 2.8, and people say that it produces the best picture quality of all EF-S lenses. The upgrade would probably cost me $300-$500, depending on the price I sell my 15-85 at, and whether I want a used or new 17-55.


But 'upgrading' from an EF-S lens to another EF-S lens is not really upgrading, is it? It is more like switching between two similar quality products. Is it worth it?


A TRUE upgrade would be to get an L lens. So, assuming that price is no object (one can only dream :(), what L lens would you recommend to replace my 15-85?


EDIT: What I would look for in the ideal replacement lens.


Thanks for all the answers so far. One conclusion I came to after reading them is that there is no point for me to invest in L glass if I care about wide angle on my crop sensor body. And I do.


I like my 15-85 because it offers me the flexibility of being able to capture moments like a few snapshots in a restaurant with friends, or my 2 years old daughter who won't sit in one place for long - definitely not long enough for me to switch lenses.


I could give up the 2mm difference on the wide end of the spectrum, if the 17-55 offered me much higher IQ than the 15-85 does.


Hence the followup question - Please let me know if you upgraded from 15-85 to 17-55 and if that was a right decision.. I know it is all personal - and that is what I am asking about - what was your experience with such upgrade if you did it?



Answer



The EF-S 17-55 f/2.8 isn't an "L" lens -- that's absolutely true. Before dismissing it, though, I think it's important to remember that Canon won't label any EF-S lens an "L" since it wouldn't work on their pro bodies. The performance of the lens, though, is considered to be excellent -- definitely competitive with "L" offerings, and very possibly even better than something like the 17-40 f/4 L, which is highly-regarded on full-frame bodies, but isn't universally loved on crop-sensor bodies. In this instance, the EF-S lens only has to serve one master, which seems to give it a bit of an advantage.



The 17-55 can't offer a couple of benefits that are reserved only for "real" L lenses -- the red ring on the lens and "real" weather sealing. The red ring is cosmetic, of course, but if that sort of thing's important to you, you'd have to paint on your own ring if you got the 17-55. Weather sealing is another matter, though. Canon's pretty wishy-washy in terms of claiming weather sealing capabilities for anything short of its pro bodies and L lenses, but the 17-55 will be better than entry-level, even if it's not up to L standards.


Since you mentioned a possible full-frame upgrade at some point, that might also be a factor for you. You wouldn't be able to use any EF-S lens with a full-frame body, but quality glass tends to hold its value very well, which mitigates this inconvenience a bit.


While you're considering options, don't forget that you'd be giving up some zoom range moving to the 17-55. That may or may not be important to you, but the zoom range of the 15-85 is one of the things I love about that lens.


Lens purchases are always incredibly individualized decisions, and there's no single right answer for everyone when it comes to choosing a lens. The factors that make a lens right for you include your intended usage and the body you'll use for it, as well. When looking at wide-angle lenses on crop bodies, don't rule out an EF-S lens just because it's not an L.


Friday, 28 October 2016

jpeg - Why is there such a big difference with these JPG file sizes?



I have 2 nearly identical JPG images that have been processed externally, but one file is much larger (in file size) than the other. I have been looking at all the metadata and embedded information but still do not know why they are different.


First file 1.46MB - https://www.dropbox.com/s/98cn46ojbqlu51q/1-1-marriott-international-inc-wounded-warriors-temp-afab192d-5424-4806-b2e6-ba3362cafb8a.jpg


Second file - 5.63MB - https://www.dropbox.com/s/42b2qzunwp79fpg/1-1-marriottmemorialday2014-142id-e98d4a3c1a4e-temp-0fbf7661-66b6-4589-944a-c67d9d8a1f89.jpg2700x2700.jpg


The only difference I can see is that the larger file has no colour profile embedded, and I believe the original of it was Adobe RGB color space. The first/smaller file is sRGB but I don't see how it could make a 4MB size difference.


EDIT: I also noticed smaller file has 583,372 colours and the larger file has 705,988 colours.


Thank you!



Answer



The main difference I see is that they're saved with different JPEG quality parameters - the smaller file has quality 91 (according to GIMP), whereas the larger file has quality 99. File size can grow pretty exponentially at high quality parameters.


Resaving the larger file at quality 91 reduces it to around 2.2 Mb, which while still significantly bigger than the smaller file is at least in the same ballpark.


Why is my Canon T3i stuck saving to internal memory instead of the memory card?


My T3i just stopped saving to the memory card and is saving to the internal memory. I have replaced the card in case it was corrupt and I have blown out the slot in the camera where it fits.


Is there a setting or something I have inadvertently changed directing the camera to save to internal memory?




aperture - What prevents a f/1.8, 24 mm - 70 mm or similar range zoom lens from being made?



I see that it is common to have professional grade lenses such as 24-70mm lenses made at f/2.8. After using a 50mm/1.8, I was wondering what would prevent a more versatile zoom lens to be made that operates at f/1.8 or even lower. I assume the prime lens can be made at f/1.2 even, because the optics are simpler at a fixed focal length. So, I'm wondering what prevents lens makers from making such a zoom lens at f/1.8 or lower. Is there a technical reason that degrades image quality (I understand the 50 is not at its sharpest at 1.8) or is it most likely a commercial decision?


EDIT: My question is different than this related question. I'm specifically asking as to why it appears in primes while it doesn't appear in zoom lenses, which the other answers do not address.



Answer




It's most likely a commercial decision based upon cost and performance.


Let's take your prime at f/1.2 example.


Canon makes a number of 50mm lenses.


The EF 50mm f/1.8 II is about $100. It has 6 elements in 5 groups, 5 aperture blades and a plastic barrel. It takes a 52mm filter and weighs 130g.


Its replacement, the EF 50mm f/1.8 STM is about $125. It has the same 6 elements in 5 groups the 50/1.8 II does, but 7 aperture blades, a metal barrel, and a step motor. It takes a 49mm filter and weighs 162g. (i.e., improvements aren't always about the optics).


The EF 50mm f/1.4 USM is about $350. It has 7 elements in 6 groups, 8 aperture blades, and a metal barrel. It takes a 58mm filter and weighs 290g.


The EF 50mm f/1.2L USM is about $1500. It has 8 elements in 6 groups, and 8 aperture blades. It takes a 72mm filter and weighs 590g. And people complain about its focus shift issue.


The (now discontinued) EF 50mm f/1.0L USM had an initial MSRP of $4000. It has 11 elements in 9 groups and 8 aperture blades. It takes a 72mm filter and weighs a whopping 985g. And everyone complained about its softness.


A larger maximum aperture implies several things in the design. A larger maximum aperture means a larger aperture opening, which in turn means larger glass elements, a larger barrel, and heavier-duty mechanisms to move these larger/heavier elements. Also, the wider the lens opens up, the more you have to deal with correction for chromatic aberration and the inherently softer the lens can get at wide open--which is, of course, where people are gonna use the sucker.


With a zoom lens, this just gets more complicated, bigger, and heavier, with more possible compromises in the design and at a much higher expense. At a certain point, it's just not feasible to try and sell the lens at the increased cost, and most manufacturers have fixed on f/2.8 as that point.



Only one brand goes faster (f/2), and that's Olympus. But they're designing for a smaller-than ASP-C four-thirds sensor, which means they can probably get away with smaller elements and simpler designs because they have a smaller image circle to project.


cleaning - Can I clean dust from a scratched sensor?



I have a camera with a scratched sensor (a Canon 1Ds Mk II) - can I clean the dust from the sensor? And if yes, how? By using the wet method? Or just by blowing air?


The scratch is in the middle. Perhaps it is better to avoid that area?



Answer



I'm not particular familiar with that specific camera but I would suggest taking it in to get the glass cover replaced. There are companies that specialises in such things. Check this thread out for details: http://www.fredmiranda.com/forum/topic/664948.


In all likelihood the scratch will be on the glass directly above the sensor rather than on the sensor itself, so it shouldn't be massively expensive.


Thursday, 27 October 2016

How to do lighting for product photography of scrapbooking stuff?


I have tried to do some simple product photographing. It is mainly some scrapbooking stuff my wife has produced, like candles and gift cards. Up until now I have been using my Nikon SB-700 for lighting. I bounce the light in the ceiling and I find the light to be rather even. However my wife is not satisfied :(



She wants it to look like this. How do I achieve this result? I have been reading some books and searching the Internet, but still I have not found any good answer to my questions.


I have found a lot of rather cheap lighning kit for product photographing. These usually include some kind of table and some halogen lights. This seems like a good choice. What confuses me is that sometimes there are some cheap studio flash kits that is said to work for product photographing and portraits. So I was thinking; why not use my studio flash with a softbox? It has a color temperature around 5600° Kelvin. I have also found some light bulbs that has a color temperature around 5500° Kelvin. Could I use a couple of them? These cost around $20 each.


All the articles I have been reading explains a lot of color temperatures and little bit on how to setup the lightning. However they do not motivate why.


Could you please help me to sort the things out?



Answer



Product photography requires some way of isolating the subject completely within the shot, and even lighting. For this reason I think you would find a light tent extremely useful.


enter image description here


A light tent has two advantages. Firstly, the translucent sides allow you to use virtually any light source (even, in a pinch, regular household lamps) as they diffuse the light evenly across the subject. Halogen lamps aren't essential by any means.


Secondly, the curved backcloth gives an 'infinity curve' effect to the photo - in other words, you can't see where the bottom ends and the back starts, isolating the subject nicely.


Prices vary by size and location, but they will rarely cost more than $30/€25. If you're on a tight budget, you can even make your own using a cardboard box and cooking paper.



astrophotography - Longer exposure & lower ISO or shorter exposure & higher ISO - what gives better results when photographing stars?


I've been dabbling with night landscapes and star photography with varying levels of success. I know I don't have the ideal lens (Canon 17-40mm f4 on a Canon 6D body) but I've seen some great shots done with the same gear. I also have a Canon 50mm f1.4 which is great but it's just not wide enough.



I usually shoot at f4, ISO 800-1600, Long Exposure Noise reduction on, 30 - 40 seconds. I find the results very noisy and the stars not bright enough. at 30 seconds stars are not bright enough and at 40 seconds they are already trailing. Here is one of my attempts.


I recently saw some photos (examples here and here) that are captured at shorter exposure times but much higher ISO (5000-6400)


I am thinking perhaps when I am close to 40 seconds the sensor is heating up more which is causing more noise? Specifically for photography stars, is shorter exposure time and higher ISO a better formula?



Answer



Noise is a fact of life when it comes to astrophotography, with the exception being stacked deep sky photos taken on a tracking mount (more in a moment).


Your photo is actually very low noise, in the grand scheme of wide field, single-frame astrophotography shots that I have seen...but it also lacks saturation. I think it really comes down to a matter of taste, but ultimately, one way or the other, you will get roughly the same amount of noise in your photographs regardless of the ISO setting. If you wish to achieve the same amount of saturation, you have to do one of two things. You are either going to need to use a higher ISO setting (ISO 3200, maybe even as high as 6400), or you are going to have to boost exposure in post. The vast majority of noise in astrophotography is from photon shot noise, so using a higher ISO is the same as a post-process exposure boost from a noise standpoint.


In your example photo, you have a wide-field, single-frame shot. Your limited to a single frame because of the foreground, unless you resort to more complex trickery where you take multiple frames, cut out the sky, and stack those frames to improve the saturation of the sky. Certainly possible...also a lot of work. Like you, I like astrophotography shots that include some of the landscape in the foreground, so it's worth trying some manual partial stacking to improve your SNR.


Heat is certainly a contributor to noise during long exposures. I am not sure that 40 seconds is long enough to produce so much heat that thermal noise becomes a more significant factor than photon shot noise. Older DSLRs used to have thermal bubbles due to overheating of near off-die components...when taking dark frames, you could clearly see regions at the corners or along edges of the frame that had more noise. I've never seen such an occurrence with my 7D, and there are times when I have taken 40-50 second long exposures at 16mm.


There are ways to reduce the various non-photon sources of noise. Dark frames and Bias frames are two. The use of dark and bias frames is usually only really necessary when doing multiple exposure stacking with a tool like Deep Sky Stacker. Generally speaking, "Long Exposure Noise Reduction" in-camera is really just taking a dark frame that is natively subtracted from the light frame before it is saved to the memory card. A single dark frame will help mitigate some read noise, but not as much as a properly stacked multi-exposure dark frame as explained on DSS's site here.





It should be noted that the most important thing in astrophotography is SNR, or signal-to-noise ratio. The higher your per-frame SNR, the better the results...stacked or otherwise. You could take 120 5-second frames, or 5 120-second frames...the five 120 second frames are always going to produce better results. You could even take 500 5-second frames, and the 5 120-second frames are still going to produce a richer result, since the per-frame SNR is much higher. Each frame contains richer, more complete information that you are unlikely to ever fully replicate by stacking much shorter exposures.


The next best way to improve SNR is to move to a camera with bigger pixels. Per-pixel SNR is higher with larger pixels, so on a per-pixel basis, your results should be better, and at higher ISO settings, than with a camera that has smaller pixels. If we were to compare the 1D X and the 7D (both 18mp sensors), the 1D X's larger pixels will each gather 2.6x more light. You are already using the 6D, which is a very good camera for astrophotography thanks to it's large pixels and great high ISO performance. From a pure SNR standpoint (based on sensorgen.info data), the 1D X at ISO 3200 supports ~3x the saturation per pixel, the 6D at ISO 3200 supports ~2x the saturation per pixel, as any one of Canon's 18mp APS-C sensors. The 6D also has the highest quantum efficiency (photon to electron conversion rate) of all Canon DSLRs (as of 2013 - later models have bested it), which means more SNR "bang for the buck".


Since you are already using the best camera you can probably get from Canon for astrophotography purposes, the only other thing you can really do is crank the ISO up. At lower ISO settings, more read noise is present. Particularly with Canon, the more you crank up the ISO, the lower the read noise contribution, to the point where at the highest ISO settings, read noise may be as little as 1.3e- per pixel (well below the flat minimum of ~3e- for the Sony Exmor found in the D800.)




Therefor, since boosting exposure post-process is the same as boosting ISO when read noise is so low, to improve the saturation of the sky and brightness of the stars, use a higher ISO setting. You said you use ISO 800-1600. Try ISO 3200, 6400...maybe even 8000. The general idea is to reduce your white point such that the camera uses it's electronics to boost the signal as much as possible before read, to minimize the impact of read noise. It should be noted that boosting exposure of an ISO 800 shot in post such that it resembles an exposure of ISO 6400 would likely result in MORE noise, as read noise at ISO 800 is more than twice as much at the lower ISO setting (5.1e- vs. 2.0e- according to sensorgen.info.)




To make things a little clearer, I've diagrammed a hypothetical astrophotography scenario. This scenario assumes a 30 second exposure at f/4, performed once for each ISO setting from 100 through 12800, using a Canon 5D III. The assumption is that a 30s f/4 exposure at ISO 12800 results in the brightest pixels (stars) reaching the "saturation point" (in other words, the brightest stars come out pure white, as any red, green, and blue pixels for those stars reach the maximum charge level). The exact same exposure at all other ISO settings will result in an exposure below the saturation point. Additionally, the difference between read noise and photon shot noise is demonstrated.


In the diagram below, the linear X axis represents each ISO setting, and the logarithmic Y axis represents charge level in electrons (e-). Red and green lines are drawn for each ISO setting, with red representing read noise, and green representing saturation point. The dynamic range is effectively the ratio between saturation point and read noise (green over red). For ISO 100, the saturation point is also the literal maximum photodiode charge level (FWC, or full well capacity). The blue bars represent the signal, and the darker part of the blue bar represents the intrinsic noise in that signal (photon shot noise, which is the square root of the signal.)


enter image description here


Assuming a 30s f/4 exposure that reaches maximum saturation at ISO 12800, the charge of that signal is 520e- (according to sensorgen.info). Therefor, assuming the exact same exposure is used for all other ISO settings...the signal, as well as the photon noise, will be IDENTICAL. (Charge in the photodiode is a product of light over time...which is affected by ONLY aperture and shutter speed.) What changes as we reduce ISO is that read noise begins to rise. Since the scale is logarithmic, ISO settings 800 through 12800 have little difference in read noise (particularly 1600 through 12800). Once we reach ISO 400, read noise starts to rise to the point where it is a greater ratio of the overall signal than photon noise.



The key difference between shooting at ISO 12800, and shooting at ISO 400, is the saturation point (green bars). At ISO 12800, read noise is low, and the signal saturates, so you'll have a bright, colorful image strait out of camera. At ISO 400, the signal is a small fraction (520e-) of the saturation point (18273e-), and will this require a significant boost to exposure in post to look the same as the ISO 12800 shot. If one does shoot at ISO 400 and correct exposure in post, then overall noise constitutes a significant factor of the signal. The read noise floor, below which useful information effectively does not exist, is almost as high as photon shot noise. Such a post-process exposure boost would result in a high degree of banding and color noise, likely right up through the midtones.


For an extreme example, if one were to shoot at ISO 100, read noise becomes the primary contributor of noise (in this particular example...keep in mind, at ISO 100, the image is severely underexposed relative to the saturation point.) Boosting an ISO 100 exposure in this case (which, in order to simulate what the ISO 12800 shot produced, would have to be a SIX STOP BOOST) would result in significant banding and color noise. The following diagram demonstrates how noise, both read and photon shot, are amplified by correcting exposure in post for ISO 100 - 6400, in order to match the ISO 12800 exposure:


enter image description here


Remember that the scale here is logarithmic, so the amount of noise for each successively lower ISO setting is exponentially higher after exposure correction in post.


optics - Why do mirror lenses have poor contrast?


I was reading this question on mirror lenses and the answers taught me a lot about mirror lenses. It is pretty obvious to me why they have donut bokeh (central obstruction) and why they are fixed aperture (an iris would be difficult to insert into the light path) but it isn't at all obvious why a mirror lens should have poor contrast.


I'm wondering why.



Answer



The loss of contrast is due to the central obstruction; that is, the "hole of the donut" that blocks light from getting through the center of the lens.


In a diffraction-limited telescope or lens, the point spread function—basically an image of a point source, like a star—is the Fourier transform of the aperture. For a circular aperture, like most lenses, this is a Bessel J1 function, also known as a Jinc, or an Airy disk:


Airy disk


When you obstruct the center of the aperture, turning it into a donut, the Fourier transform changes in a way that transfers power out of the central bright spot, into the first ring. The effect is to lower the contrast of the image.


This web page has examples of the point spread function for all sorts of obstructed apertures, so you can see the effect clearly.



shooting technique - Tips on getting group shots for family


My grandfather is turning 80 this year in September. The most important thing to him is his family. Because of this, my entire family is getting together to celebrate. Since the family is spread out all over the country, it is rare that we all get together.



I have been tasked with taking photos of all the family and I am stressing out about it. I don't believe that I am a total noob when it comes to taking pictures, but I am most definitely not a professional either.


The camera I have to work with is a Sony Cybershot DSC-H2


I will have to shoot 15 adults and 5 children (the oldest having just turned 5 and the youngest being around 18 months). I need to get a group shot as well as shots of each family on their own. I also plan on getting a shot of all four generations together. I should also mention that this shoot will take place outdoors.


Does anyone have any tips, tricks, or ideas that could help me? I am especially nervous about getting good pictures with the kids.




Wednesday, 26 October 2016

nikon - Is it possible to take a self-portrait using a flip rotatable screen DSLR involving the hand ONLY?


Is it possible to take a self-portrait using a flip rotatable screen DSLR for example, like Nikon D5200 and involving the hand ONLY?


I haven't found much research on this on the internet so was curious to know as I'm planning to buy Nikon D5200 with the 50mm 1.8 lens



Answer



Of course!
BUT odds are that your head (or hand) will occupy MUCH more of the image than you are happy with.
ie not really if purely hand held.


You can





  • Prefocus camera place on semi stable location (backpack/table/rock, sheep, ...) use a 2s or 10s timer
    trigger camera and step back Survival of camera depends on stability of sheep etc.
    Or on the ground. The ground is often nice and stable. Not always.
    Shop shelf or Ground or Ground? - this was 10 second timer on table or similar - probably self timer on table maybe not. Ground vertical




  • Hold camera by outer end of lens and use eg 2s timer. With practice you'll get photos from slightly further away, but not far enough at 50mm + APSC (I just tried).




  • Use a mirror. Yes, that's cheating, but it works. Maybe not quite like this , but it gives the idea.





  • Use a low cost low quality front of lens add on. These are usually not suited to quality photos but often good-enough for trip-record / fun self photos. Playing with various lenses intended for other purposes may turn up something that works 'well enough'.




  • Buy a really really really awful tripod - the sort that sell for about $US7 equivalent in NZ. These will mount a DSLR but as a atripod for normal use they are ultra marginal. As a tripod when you have no other and MUST have one they are still marginal, but may be better than nothing.
    As a short DSLR selfie stick they may suffice BUT be sure to use the camera strap as an 'arrest' should the camera fall.




  • An only slightly dearer tripod can work quite well.







Cheapo tripod as selfie-stick.


This was probably at 17mm with an APSC sensor but demonstrates the 'long arm,' / tripod-selfie-stick method being applied. A light weight but not totally junk tripod is extended as required - probably about 2 leg sections here. Mount camera pointing (what would usually be) down along the legs.
Hold tripod by enough of leg ends to get adequate leverage.
Use camera strap attached to you somehow to (try to) present total disaster.
Camera is manually focused (more or less), self timer is set to 2 seconds.
Stabilise self - lock arm through handrail or whatever - falling off a train at 60 mph not recommended (nor at most other speeds).
Swing camera in to where shutter release can be contacted - a remote would be marvellous. Activate timer, swing camera out. Oh well - try again

10 second timer and flip over screen more predictable.


I don't know what all the blue is - looks like massive CA but the lens wasn't that bad. No matter - photo quality is definitely a secondary issue in cases like this.




BUT - 50mm really is not what you want to use.
Here are quite a few mostly-arm-unseen Old Grey Guy images.
Some are obviously not hand held by me - most are. That's at 17mm APSC in most cases. At 50mm you only get 17/50 = 34% as long sides and area is 34%^2 ~= 12% of the area at 17 mm !!!!


http://bit.ly/RedolentRedundancies


enter image description here


Comment from timeline:




  • Train-splatting - Malaysia. This is "safe enough" as long as you are constantly aware. She wasn't. I had to point out how rapidly posts, trees, bridges and other assorted things creep up on you at 60 mph+. Hopefully I managed to convey the point. This is looking into direction of travel.


photoshop - Stitch first and edit later or vice versa?


I have a set of three images imported in Lightroom 3.6 which I want to stitch into one panorama using Photoshop's CS5.5 Merge to Panorama tool. As I see it I have two options in doing so.




  1. Doing all modifications (colour, brightness, contrast, etc...) first, syncing the changes between the three photos and then stitch them together.





  2. Stitching the photos first and then use Lightroom to apply modification to the whole image.




Which of these two methods is considered to be best practice?



Answer



As a general rule, the stitching program should get the highest possible detail of the images, allowing it to make the best out of it. Therefore, I would not pre-process the images as it might degrade the information.


However, if you have a large amount of input images, it might get difficult to work with the resulting large picture afterwards, due to your PC's memory and CPU constraints. Only then I'd revert to pre-processing.


There's only one situation where I was forced to pre-process: When I had images of varying brightness, due to having taken them close to sunset, and the light getting darker during the panoramic 360 session, so that last image was darker than the first, making it hard to get them properly stitched. In this case, I had to gradually adjust the brightness of all images to make the last one match the first one more closely before stitching them.



scanning - Where is a really good place to get film developed by mail?


I'm looking for a place to get my 35mm film (color slide and B&W) developed and scanned by mail with a focus on quality. I have a good local shop about 10mi away from me that does great development but horrible horrible scanning and its a PITA to drive up there.



I noticed another person asked about online photo developing with an eye on inexpensiveness, but I'm looking for quality developing/scanning, something on par to if I did it myself with my Nikon 5000ED scanner (which I'd like to sell as I don't want to do it myself anymore).



Answer



I have been looking for film developers, too.


I stumbled upon Ken Rockwell's recommendation of North Coast Photo http://www.northcoastphoto.com/


I haven't used them myself.. so can't speak.


autofocus - How does (auto-/manual-)focus changing work?


I know when I change focal length of a zoom lens the physical length of it is changed. It's understandable: the optical parameters of the lens were changed.


But what is going on when (auto-/manual-)focus is changed? What is changes in my primary fix lens if I focus on different distances? The physical length of the prime lens is the same.


In general, how does (auto-/manual-)focus changing work and what is difference between focus changing and focal length changing?



UPDATE: this question isn't actually about how manual focus works but about similarities and differences between focus process and changing focal length in zoom lens



Answer



SONY alpha lenses, like many other brands, are internal focusing.


Internal focusing



Only the middle groups of the optical system are moved to achieve focusing, which leaves the total length of the lens intact. Benefits include fast autofocusing and a short minimum focusing distance. Also, the filter thread at the front of the lens does not rotate, which is convenient if you’re using a polarizing filter.



enter image description here


This means that the actual length of the lens does not change during focusing. This was not always true. Nikon for example, only began manufacturing internal focusing lenses in 1976. They are designated IF.


From Ken Rockwell's Nikon lens site:




"Internal Focusing." In the old days, the entire lens had to move in and out to focus. Telephoto lenses had to be designed with huge focusing tracks just to let them focus at all, and they couldn't focus very close because the helicoids just weren't long enough. The long focal lengths meant that there were long distances the lens had to move to focus.


Nikon discovered that one could focus the lens by just moving some elements around inside the lens barrel.


IF lenses focus closer and faster than conventional telephoto lenses. IF was a fantastic innovation for telephoto lenses when Nikon invented it in the 1970s for the manual-focus super teles. Today, most modern AF zooms, super teles and some macro lenses use this technique. It helps AF lenses focus quickly because there is less glass to have to move around.


The optical trick is that the internal elements move slightly to shorten the lens' actual focal length as one focuses closer. This lets these lenses focus very close. It also means that when compared to a traditional lenses that the IF lens will appear to have a slightly shorter focal length than marked at close distances. This discrepancy disappears at infinity.



Some prime lenses are not technically IF.


For example, the Nikon 50mm f/1.4 AF-S:



This isn't technically an internal-focusing lens, as the deeply recessed front element extends towards the front of the barrel at close focus distances. However, the overall length of the lens remains unchanged and the front element doesn't rotate during focusing




exposure - What is the best way to handle overexposed sky in post-processing?


I'm new at photography and I have taken some pictures where the subjects in the foreground are exposed correctly but the sky is very overexposed. What is the best way to handle it in post production?


(I have pictures in RAW format.)



Answer




I use Apple Aperture, and this is my normal way of dealing with an overexposed sky (or anything overexposed for that matter)



  1. Turn on overexposure highlights (option-shift-h), to show where detail is lost to overexposure

  2. Turn up the "Recovery" slider in the "Exposure" plug-in, until no overexposure is shown (or until the slider is at max). Recovery will bring down the exposure of overexposed bits of the photo.

  3. Turn up the "Highlights" slider in the "Highlights & Shadows" plug-in until the image is visually pleasing (you get the details you are looking for, e.g. interesting cloud formations)

  4. Adjust the the Levels.


Tuesday, 25 October 2016

workflow - What sites exist for posting client proofs?




As I'm doing more and more photo shoots, I'm looking for a site in which I can post proofs for clients to look at. I would use Flickr, however the images can be downloaded and I obviously don't want proofs to be downloaded before they have been edited. Can anyone recommend a site that I can use?




Monday, 24 October 2016

Having difficulty lighting various reflective product packaging- use dulling spray?


Beginning photographer, first post- I'm trying to merchandize and shoot a product composition with a lot of beef jerky packages. The crinkly reflective packaging is proving really difficult to light.


so many shadows and reflections :(



We're using a Cannon T4I with two strobes on a table with a backdrop.


I've read about dulling spray on some other forums- could this be a solution? Anyone have specific product recommendations?




maintenance - How long should a lens last?


There are plenty of ratings and tests for how long DSLR bodies last, but I have never really seen much that describes the expected lifespan of lenses.


Recently, one of my cheap-o lenses (Nikon 18-55mm, ~10,000 exposures) started making some funny noises and the focus ring jams up occasionally. It has been through a lot (got frozen in China, and bounced along trails on the back of a motorcycle in the Rockies), but I expected it to last a little longer than a couple years, especially next to my 20 year old 80-200mm which gets twice the usage.


Anyways, how long it is reasonable to expect a lens to last before needing to be serviced or replaced?


Are there any brands/lines of lenses that do better than others (and vice versa)?



Answer



This doesn't quite answer your question, but it's relevant: there is value in using your equipment in the way that best serves your photography, even if it's not ideal treatment for the equipment. So for example the freezing and bumping along on a dirt bike aren't super great for the lens, but it sounds like those things were essential to having the equipment in those situations at all. It's not an expensive lens, so maybe you got your money's worth.


In other words: treat your equipment as well as you can, but a little abuse may be the price you pay to get a given shot. And maybe that shot is worth the price.



Adjust exposure compensation in manual mode?


The only way to manually adjust exposure compensation is to use either P,A,S or modes, however then of course something else is automated. In full manual mode you can not change exposure compensation ?



Am I mistaken, why is this ? Are other advanced cameras like this ?



Answer



This question tells me you should start by understanding exposure first. Start with reading about the Exposure-Triangle. If you understand that, you would not be asking this :)


Briefly, exposure is determined by 3 parameters: ISO, Shutter-Speed and Aperture. When you are in manual mode and set all these, that is it. No further adjust is possible or needed.


When you are in an automatic mode, you adjust 0, 1 or 2 of these three and the camera determines the rest. The point is that there is at least one left. Exposure-Compensation shifts how the camera sets the parameters it controls. If it cannot control anything as in manual mode, there is nothing to shift.


Most mid-range cameras with manual-controls and a single control-dial use this to their advantage where the EC button switches between controlling aperture and shutter-speed in Manual mode. If your camera has dual control-dials, EC either does nothing or shifts the Exposure-Meter which can be used as a guide to set Manual exposure. It does not affect exposure in this case either.


Saturday, 22 October 2016

Is the formula for object image size given focal length, etc. independent of sensor size?


I am trying to figure out how big an object of, say, 50cm height at 100m distance and 600mm focal length would appear on a camera's sensor. The ubiquitous formula


object size in image = focal length * object size / object distance

yields


object size in image = 600mm * .5/100 = 3mm


What I am wondering: Are these 3mm entirely independent of sensor size?


E.g., a specific superzoom model has a 1/2.3" sensor (= 4.55mm height according to one source) and a maximum zoom quoted to have a "35mm equivalent focal length of 600mm". Would the object actually cover 3/4.55 = approx. 66% of this sensor's height = 66% of the image, or does the relation between the sensor size and the "35mm equivalent" have to be taken into account somehow?


(My apologies if this has been asked before - I have found many related questions, but not this one.)



Answer



The answer to your question generally is yes. However as you mention, the ratio of how much of the overall image your subject takes up will depend on your sensor size. What you do have to watch out for is that the "35mm equivalent focal length" should not be used but the actual focal length as quoted on the camera specs - this is usually something in the single digits of millimetres.


The 35mm equivalent is for comparison purposes only because it reflects the equivalent area of 35mm film (or a full-frame digital sensor) - i.e. 36 x 24mm. People tend to be most familiar with the range of focal lengths at this sensor size e.g. 24mm is wide, 50mm is normal, anything about 100mm is telephoto and so on. This is simply the real focal length multiplied by a factor that represents the ratio between the camera's real sensor size and the nominal 35mm sensor size.


Which color settings to chose in Photoshop and Aperture with an Epson SPR2880 printer


My workflow consists of importing photos into Apple Aperture, where I do most of my editing. Sometimes, I edit the photo in Photoshop. Aperture can automatically create a .psd file based on my edited image, and include that in its own library. The final results gets printed on an Epson Stylus Photo R2880 printer.


In the Aperture settings, I can select which color space to use when generating the .psd file. As I have set it up right now I use 16bit and ProPhoto RGB color space.


However, when opening up the color utility, I can see that some of the glossy paper color profiles for the printer contains colors that are not inside the ProPhoto RGB color space. This is mainly blue and purple nuances in the black area that are outside the scope of the ProPhoto RGB color space.


What puzzles me is that the icc profiles for my printer, an Epson Stylus Photo R2880 are not CMYK, but RGB profiles, I am wondering if I should choose one of the color profiles for that printer when exporting to PhotoShop. The annoying part about that setup is that I would have to go into Aperture preferences and select the export color space based on the papertype I wish to print on before opening an image in Photoshop.



What also puzzles me is the fact that the icc profiles for the printer use the RGB, not the CMYK, color space. Although the printer does have 8 instead of 4 types of ink instead of 4, it is still based on subtractive color, as opposed to additive color that the RGB space is.


I'm quite new to the entire color management thing, and I want to set up my system to be able to generate predictable prints, and also fully utilizing the capabilities of my printer, e.g. I can see by comparing the color profile of my monitor with the color profile of the printer that the printer by far exceeds the monitors capabilities in producing very saturated green and blue colors.


My primary workstation is an iMac, on which I have calibrated the display using a x-rite Colormunki.



Answer



Working color spaces and print color spaces are distinct, separate things. Generally speaking, you never want to directly apply a print profile to an image. The purpose of ICM is to utilize ICC profiles to describe what needs to be done when moving content from one device to another. You NEED to keep your photos tagged with an RGB ICC profile that properly describes the image in the RGB space, and you NEED to select an additional ICC profile that properly describes the capabilities of the printer. The ICM engine will then (normally) figure out how to adjust colors...according to your selected rendering intent...from the RGB space to the printer space.


To demonstrate my workflow, I generally do the following:



  1. Do primary processing in the largest RGB color space I can (normally ProPhotoRGB).

  2. Create a copy of my primary working image, and convert to an RGB color space that as closely matches the gamut of the print as possible.


    • This may be sRGB if the paper is a limiting factor.

    • This is often AdobeRGB, as my Canon PIXMA Pro9500 II supports a gamut that largely covers the AdobeRGB gamut



  3. Manually scale the print copy to the exact dimensions necessary to accommodate my print.

    • If printing at 300ppi @ 19x13", I would scale and crop the image to 5700x3900 pixels.

    • Perform any print sharpening necessary to bring out desired detail

    • Preview at "print size" using the zoom tool (make sure you configure Photoshop with an accurate screen PPI...the Apple CinemaDisplay 30" has a 103ppi resolution)




  4. Soft-proof the print in Photoshop, by selecting the appropriate printer ICC profile that matches the printer AND paper I intend to use

    • First and most importantly, I try to adjust black and white point to lie within the limits of the print gamut

    • If necessary, more so when using Relative Colorimetric rendering intent than Perceptual rendering intent, fix out-of-gamut color (search the web for a variety of techniques for this)



  5. Print, leaving the image profile what I selected in step 2, and selecting the same ICC print profile as in step 4


I want to stress at least checking the white and black points when in soft-proofing mode. Using a Perceptual rendering intent when printing will usually do a pretty good job, but its easy to lose a lot of tonality in the shades and sometimes in the highlights if you don't adjust them for the specific printer and paper you intend to print on. Adjusting them in soft-proofing mode ahead of time helps maximize tonality for print. Generally speaking, you don't need to worry about out of gamut colors if you convert to an RGB space that closely matches the printer space. With modern Epson printers, that is probably closer to AdobeRGB than sRGB. If you prefer to use Colorimetric Rendering intent, then you might want to learn some techniques to fix out of gamut colors before printing, to maximize your control over color quality and minimize posterization.



Finally, once you have tuned the print copy for the specific paper and printer, save it with all your adjustments. You should be able to print from it as many times as you need with predictable results. If you ever need to print on a different printer, paper, and paper size, you should redo steps 1-4 above for each one, and save a separate copy off for each.


Should two identical digital pictures of the same resolution and format have the same size?



I apologize if this is the wrong site, but I thought my question might be too specific to photo encoding. I recently recovered a host of digital picture files from a dead drive and after the recovery noticed that although all the photos are the same resolution and are one of three encoding formats (jpg, png, or tif), there are drastic differences in their file sizes. I know the efficiency of the compression can vary to a certain degree between photos, however, there are some as small as 112KB and others into the hundreds of megabytes. With the really enormous files I was pretty confident that the recovery tools just scraped some extra data into the photo files, so I started going through, opening the photos in paint and then re-saving them and files that were up to approx 300MB were encoded at just 600KB.


It got me wondering, if I open two files in paint and they are the same resolution and each pixel is the same color (ie, they look identical), can there be other data behind the scenes I'm not aware of that paint is cutting out that is important to the image, or will the encoding on two files of the same number of and color pixels be the same and result in identical sizes?




Friday, 21 October 2016

Does stacking more lens filters decrease overall image quality?


As commented by t3mujin in another question:



Stacking filters will decrease image quality, as it's another piece of glass light has to go through before reaching the sensor.



I was wondering whether this is true, or better yet, how radical the quality decrease really is?


I was thinking about using UV filter on my lens and on that, stacked a polarizer. This combination of filters sounded to me like a great idea on how to shoot the nature, but after I read the aforementioned, I'm really wondering whether I might be wrong.


What would be the best option for this situation?




Answer



Anytime you add something in the optical path you will lose quality. The quality you will lose depends on the filter quality, filter type and lighting conditions.


Most filters are extremely susceptible to flare because they add a flat reflective surface and can take a great image and make it completely unusable. That does not mean you should never use a filter or even more than one, but you should do so for a valid reason knowing the sacrifice you are making at the same time.


Polarizers have specific usage and an effect which cannot be simulated by software, so use them to cut-down reflection, increase saturation in the sky, etc. No need to add it over another filter that essentially does nothing.


UV filters have a use too but are rarely actually needed. They are usually recommended at high-altitude but AWB or custom white-balance takes care of that. Since they are cheap and do not cut-down light by much you can use them to protect your lens when it is in eminent danger such as near salt-water and flying sand.


Against knocks, a lens hood is much more effective protection and may even increase image quality by reducing flare from stray light.


sigma - Are Canon extenders compatible with non-Canon lenses?


I have two APS-C (70D and 600D) bodies with Canon EF and EF-s lenses, and Sigmas, among them the Sigma 70-200 f2.8 HSM OS. I am also considering getting the new Tamron 150-600 lens, pending reviews.


I was just curious if a Canon extender, specifically the canon EF 2X III, will work on the Tamron and/or Sigma lenses. Note that I currently own the Sigma 1.4x teleconverter but I'm not very happy with its IQ.




Does Lightroom export white-balance temperature and tint value to JPEG metadata?


When I export a JPEG from Lightroom 3.6, is the white-balance temperature and tint value written in the JPEG file somewhere? Could I later take that JPEG and see (in the EXIF for example) what the WB values I used in the developing process are?



Answer



When you export from Lightroom (via the dialog, rather than using a predefined preset), there is a section in the Export dialog called 'Metadata' which allows you to control the amount of detail contained within the metadata. If you set it to maximum (I use LR4 so can't tell you exactly what the options are in v3.6), then the white balance and tint will both be contained within the exported file's metadata.


If you open the JPEG file in Photoshop and view the raw metadata, you will come across the following section:


As Shot
4850

+1

This contains the information you need.


To view the raw metadata go to File -> File Info... and then click the tab labeled Raw Data. There you can type in WhiteBalance in the search field, which will lead you to the white-balance information.


Thursday, 20 October 2016

post processing - When is black and white likely to enhance an image?


I recently had a play with converting some images to black and white to see how that changed the image. Some baby photos came out particularly well, while others I tried seemed less interesting when in black and white.


I'm wondering what causes things to look more or less interesting in black and white. Are there any subjects which generally look better in black and white? Or are there particular qualities of a photo which might make you think something would look better in black and white?


Things I've thought of from my own playing around:



  • Black and white images prevent the eye being distracted by different colour objects, so the eye may be more drawn to the intended subject.

  • When the colours are a strong part of the image (maybe in a festival or market), they are unlikely to look better as black and white.


Are there generally accepted criteria (or rules of thumb) or is it a purely subjective judgement?


Here's hoping I'm not going to start a holy war - I'm genuinely interested if there are any rules of thumb for when black and white is likely to be a pleasing transformation.





Why does a bigger sensor lead to a shallower depth of field?



It has been mentioned at a few places that a larger sensor results in images with a shallower depth of field. Example image:


APS-C Canon 30D left, FF Canon 5D right, same lens, same composition, both f/2.8



APS-C Canon 30D left, FF Canon 5D right, same lens, same composition, both f/2.8



I understand how sensor size would relate to, for example, field of view, but the relationship with depth of field does not seem straightforward.


It actually seems contradictory - I have more wells on my sensor, and I am able to focus on less number of points.


What is the reason for this effect?



Answer



Firstly, the number of wells on the sensor has no bearing on where you can focus or 'how much' you can focus on. Out of focus light is still light hitting the sensor.



Simply put, you have shallower depth of field with a full-frame sensor because you have to get closer to the subject (or zoom in) in order to fill the frame. Note that in your example it says same composition: the camera has been moved or the focal length changed in order to fill the frame with the bottle.


To put it another way, if you fix a tripod in place and take a shot with an APS-C camera with the bottle filling the frame, then take the same shot in exactly the same position with a full-frame camera, you will have more space around the bottle. So you will either need to zoom in or move the camera closer to achieve the same shot where the bottle fills the frame, either of which will alter the depth of field,


See this excellent summary of sensor sizes and their effects.


Wednesday, 19 October 2016

canon - How do I enable back-button AF on the 760D



I have an EOS 760D (recently upgraded from a 30D - yay!), and I'm can't find the custom function that allows you to use back-button AF. Does the 760D have this feature at all or has it been omitted? If it does, could someone point me to the menu item that enables it?



Answer



Go to page 357 of the 760D manual. You need to use a Custom Function to change the AE Lock button to a Back Button focus button.


Use C.Fn-10 set to option 1.


Here is a video that also describes how to do it: How-to back button focus on the Canon T4i, T5i, T6i, T6s


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aerial photography - What is the x and y camera gimbal angle for a drone?


I was looking at this question. How do I calculate the ground footprint of an aerial camera?


I'm trying to calculate the area a photo footprint captures depending on the elevation of a drone. This answer explains it very well, but I'm having trouble understanding the x and y-axis gimbal angle the answer describes.


In particular, for mapping applications a drone's camera is normally not directly pointing down, but instead point a bit forward, perhaps 10 or 15 degrees. I'm wondering if this is the x-axis or the y-axis. In most examples, both the x and the y axis angle are the same, but this doesn't make sense, since most drones, like the DJI Phantom 3 has a camera that only moves along the up and down axis.


Any help would be greatly appreciated.




Tuesday, 18 October 2016

Camera dynamic range and Lightroom exposure slide


I have the Nikon D600, at ISO 100 has more then 14 EV of dynamci range. Now if I shoot a photograph in raw file and open it in Lightroom, with the exposure slide I can go only +5EV and -5EV.


I am confused, does that mean the in Lightroom I cannot use the full dynamic range of my camera? How I have to interpret the +5 when I push the exposure slide all the way to the right for example?


Thank you.



Answer




You are confusing the dynamic range that can be contained in a RAW file with the adjustment that tells Lightroom what portion of that dynamic range to place in the center of the displayed picture's dynamic range.


A photo can have some parts that are so bright they are pure white and other parts so dark they are pure black. The distance between the white parts and the black parts, expressed as Exposure Values (EV) are the image's dynamic range.


Your camera can detect differences in brightness of about 13 stops (the other EV in the camera's DR is eaten up by the noise floor - the level of brightness that is indistinguishable from digital noise). But the best an 8-bit image, such as a JPEG, can do is somewhere between 6 or 7 stops. This means a typical monitor that is 8-bits per color channel is also limited to about 6-7 stops. So are most printer ink and paper combinations.


When you open a RAW image in Lightroom, what you see on the screen is an 8-bit conversion of the RAW data using your LR default settings. As you move the controls, including the exposure slider, LR recomputes that 8-bit conversion and displays the results. Once you are happy with your edits, you can export the image and the conversion you see on the screen is saved as an 8-bit JPEG.


Some of the adjustments you can make in LR squeeze the wider 14-bit range between the brightest and darkest areas of the scene into the narrower range of an 8-bit image. With the exposure adjustment, though, you are telling LR to shift the point at which everything brighter than a particular brightness value is rendered as white and everything darker than a particular brightness value is rendered as black without changing the distance between the white and black points.


See also When comparing sensor dynamic range, what are those numbers based on?
And What does a dynamic range difference of 2.7 EV really represent?


is uv filter a must?



I am using panasonic 25mm 1.7 lens in olympus omd-em10 ii body. Neither of them have a uv coating. Will it hurt lens/processor health if I use it without filter?




cleaning - Remove spot on sensor Olympus OM-D E-M10



I've got a visible spot on the sensor of my OM-D E-M10 (Mark I). I think it's a tiny splatter. Can I clean it with a cotton swab and some alcohol for example? I assume there is a piece of glass in front of the sensor?





equipment protection - Is the Canon 60D weather proof?


Is the Canon 60D weather proof? I know it is not stated in the manual, but has anyone tried using it under light rain?




Sunday, 16 October 2016

What is a reasonable file format for film scanning?


I'm looking to use my CanoScan 8600F to digitally archive the photos I've shot on film.


The issue I've stumbled on is deciding on a file format. Ideally I'd like something that is lossless but with some reasonable compression.


So far I've tried (over the last few years):


TIFF - File sizes seem to be pretty big


JPEG2000 - Photoshop elements 4 supported it, but doesn't seem to have a lot of support else where


DNG - Not sure if this is an option for scanning


I'm also looking for some guidance on resolutions to scan at... this was asked in another question "What to consider when scanning 35mm film (and scanning in general)" but wasn't directly answered, other than to say that scanners were only optically capable of 1500dpi.


With some exceptions I don't expect to make prints other than maybe 4x6s.



I currently use Adobe Lightroom with my DSLR and my new laptop included Photoshop Elements 9, but I haven't used PE9 yet.



Answer



I would say TIFF is probably the best format. JPEG 2000, like JPEG, is still a lossy compressed format when you really try to save space (the lossless version can compress a bit, but not nearly as much as the lossy form, and some forms of the "lossless" wavelet compression still can't fully reproduce the exact original image.)


When scanning in an original or master image, it's really best to maintain as much image detail and color depth as you can, and TIFF is an ideal format for this. It is guaranteed to be lossless, supports a wide variety of color depths including high color depths, has very broad support across many applications on multiple platforms, and even supports layers and other advanced objects that can be created with applications like Photoshop. TIFF also supports the storage of metadata, like JPEG.


I am not sure if DNG is an option for directly scanning film, and even if it was, I am not sure what the benefit of using DNG over TIFF for a film scan is. DNG has more merit in the digital RAW workflow, as it supports storing native camera RAW data and metadata, which really wouldn't be of much use for a film scan (which is always going to result in RGB pixels anyway.)


Regarding resolution, I guess it might depend on the nature of the film. If you are scanning very grainy film, you might not need to scan at an extremely high resolution, however scanning at too low of a resolution will likely even interfere with grain detail (which does have an aesthetic appeal to many, and that aesthetic might be diminished at too low of a resolution... and I would consider 1500dpi to be fairly low these days.) I'm a digital photographer, however I have researched film quite a bit as I have a strong interest in large format. To my understanding, a low-speed, fine-grain film like Velvia 50 is easily capable of over 3000dpi, which is double the dpi mentioned in the article you have linked. I have done some 35mm negative scans of old film just for kicks, and scanning up to 4800dpi (the maximum optical native of my scanner) produces an astonishing amount of fine detail. I would say scan at the highest resolution you can so long as you don't see negative returns, and I wouldn't be surprised if 4800dpi or even as much as 6000dpi was necessary to extract all the detail from your film.


If the initial file size worries you, you can always downscale your master file a bit from a high resolution scan, which should help improve sharpness a bit while also saving a little disk space. High-ISO black and white film will generally require less DPI, however keep in mind that film grain is not ubiquitous in size and distribution, and the full quality and shape of a single grain may require many pixels to render fully.


lens - Is the Panasonic Leica Summilux DG 25mm f/1.4 as good as the name implies?


I’ve got a soft spot for fast, normal lenses, and while I normally shoot with a Pentax DSLR, Panasonic’s Leica DG Summilux 25mm / F1.4 ASPH has had me sneaking drooling glances at Micro Four Thirds for a couple of years.


The lens has the high-prestige Leica name, has a nice fast maximum aperture, and does reasonably well in technical reviews from PhotoZone and SLRgear. But how does it handle in real-world experience?



Answer



As it happens gave me a chance to try it out, with the (no longer active) Gear Grant Program. I rented an OM-D EM-5 body and the lens for a couple of weeks, and took it with me everywhere.



My first impression was slight disappointment — although it's a mix of metal and plastic construction, it feels much more plasticky than Pentax's "Limited" primes, or Fujifilm's new 35mm f/1.4 which fits the X Pro-1. The face of the lens notes Leica , but the outside lens body is all Panasonic-consumer-product. There's nothing wrong with it, but it's not packaged for love at first sight. But, that's pretty shallow of me! Judging a lens by the outside is far worse than judging a book by its cover. So, I got over that as quickly as I could, mounted the lens on the Olympus OM-D EM-5, and started taking pictures.


And that's where this lens lives up to my expectations. It's really, really nice. It focuses very quickly even with the contrast-detect system used by the OM-D EM-5; it has nice, smooth bokeh; and it produces images with no visible technical defects in almost every situation I used it in.


Now, while I do make some photographs with the purpose of creating art, usually my goal is unpretentious — I want nice photographs of my kids. I try to make sure my hobby doesn't stray too far into gear obsession, so I normally try to resist the typical test shots and just focus on doing what I'd do normally, which this lens handles very nicely:


f/1.4, ¹⁄₁₂₅ second, ISO 2000
f/1.4, ¹⁄₁₂₅ second, ISO 2000


f/5.6, ¹⁄₈₀ second, ISO 250
f/5.6, ¹⁄₈₀ second, ISO 250


Both of those are JPEGs straight out of the camera with nothing done to them except a square crop and scaling for the web. (A tangent on the camera — the palms of my daughter's hands are a little overexposed in the butterfly picture, but there's actually a lot of detail there even in the JPEG and it could be recovered nicely with a little bit of effort.)


Both of these are family snapshots, but if you want to justify buying a fancy lens for that purpose, these seem like pretty good situational examples. The nice wide-open performance makes the hula-jump picture successful without requiring a super-jacked up ISO (it's pretty high as it is) or getting more motion blur than I wanted. And the detail in the butterfly picture is stunning. Here's a 1:1 crop from another, just to show — and this one taken wide open:


f/1.4, ¹⁄₁₂₅₀ second, ISO 200 (noise reduction disabled)

f/1.4, ¹⁄₁₂₅₀ second, ISO 200 (noise reduction disabled)


Now, that's not the level of amazing quality we're used to seeing from dedicated macro lenses in the hands of insect shooters. But, this crop is just 2% of the full image! That's like using a 5.75× digital zoom — basically pretending that this is 300mm-e lens. And again, this is with the aperture wide open.


So, those kind of results made me pretty happy, but because of the hype I'd felt about this lens, I did a few test-style shots as well. If you look at the crop above, there's a little bit of purple fringing in the blurred thumb. I wanted to investigate that a bit more….


Busy, high-contrast scenes produced by tree leaves against bright sky are one of the most common "challenge" situations for a lens. Here's a 1:1 pixel-level crop from an out-of-camera JPEG:


Purple fringing at f/1.4


So, yeah, that's got a lot of purple fringing. Pretty ugly, really. But here's the kicker — that's at f/1.4, wide open. There's really no reason to do that. (In fact, my shot is slightly overexposed, because the camera was at fastest shutter speed and lowest ISO.) Dropping down to just f/2.8 gives this:


Purple fringing at f/2.8


Problem gone! That means in most real-world use, this issue is unlikely to be seen, even if you're really looking for it.


This lens also produces very nice bokeh:


f/1.4, ¹⁄₆₄₀s, ISO 200 (center crop, scaled 25%)

f/1.4, ¹⁄₆₄₀s, ISO 200 (center crop, scaled 25%


Even with a busy background, that's quite smooth and visually pleasing. Here's a 1:1 crop of a detail, showing the highlight circles:


wide open circles


Generally, very even and balanced, with no donut-shape ringing. One might not exactly call it "creamy", but it's basically what one would hope from a modern, well-balanced lens. Where I think the results shine is stopped down a little bit. Here's f/2.8, f/4, and f/8:


circles, f/2.8
f/2.8, ¹⁄₁₆₀s, ISO 200 (center crop, scaled 25%)


circles, f/4
f/4, ¹⁄₈₀s, ISO 200 (center crop, scaled 25%)


circles, f/8
f/8, ¹⁄₂₀s, ISO 200 (center crop, scaled 25%)



You can clearly see that although the lens specifications boast of a "circular aperture diaphragm", the seven blades are readily apparent in the highlight shapes. To my eye, though, the results are gorgeous stopped down, with beautiful rendering of enough detail to understand the context without being overwhelmed by busyness. Good stuff.


Further tests might involve brick walls and lines-per-inch charts, but honestly, those don't measure things I care about very much. I've read in technical reviews that distortion is low, and there was never anything that jumped out at me as problematic. And, in looking at the actual images, there's all the sharpness I need — in fact, at the 1:1 crop level, noise from the Olympus sensor is a bigger concern for pixel-peeping. In any case, the sharpness is well above my pickiness threshold.


So, in conclusion: yeah, I really like this lens, which won me back over with results after initial (admittedly shallow) disappointment with the packaging. I'm not ready to switch all my gear, but if I do end up owning a Micro Four Thirds system at some point, this lens would certainly be a central part.


In the garden
Like the other images in this post, this is straight JPEG from the camera.


I like to use nice gear for my garden snapshots. But if you're aiming at something different, this lens can probably take that too.



All photographs copyright © 2012 Matthew Miller, and licensed CC-BY-SA 3.0 at this resolution.



Saturday, 15 October 2016

camera settings - Why doesn't wifi on canon 70D connect to my Android device?


Just this past weekend, I got a Canon 70D, and I was so excited especially because of the wifi functionality. So I got all set up on my camera, and also got the EOS remote from Google Play store. But when I go into the app and try to connect, it doesn't even show my camera.




Friday, 14 October 2016

How do different aperture and shutter settings affect a photo with the same overall exposure?



Ok, here's my doubt. Suppose I want to get a certain exposure for an image. Keeping the ISO constant, there are two tentative possibilities here:



  1. Put the camera at f 1.4 (say) and at 1/1600 shutter speed (suppose).

  2. Put aperture at f 8.0 (say) and shutter speed at 1/50 (suppose).


Both would get me the exact same exposure. Yes, for the latter, I may have to use a tripod. But the question being, what would be the difference in the image thus obtained? I can fairly interchange the settings for the same shot (theoretically). Or can't I?



Answer



Different shutter speeds have an obvious different effect: more motion-blur. (That includes both subject motion and blur from any motion of the camera itself.)


Different apertures also produce different results; most notably that depth of field increases as you stop down. So, f/8 gives you a much deeper in-focus area than f/1.8. This effect is lessened on a smaller sensor (or, if for some reason you just crop out the center part of the image and blow it up), to the point where it's basically a non-factor on most point & shoot cameras.


But there are other effects of changing as well: lens sharpness, contrast, and vignetting characteristics change, usually improving significantly when you stop down a bit. (For a certain look, though, that technical improvement may not, in fact, be what you want.)



That's assuming perfect reciprocity — the idea that aperture and shutter speed really are perfectly interchangeable for exposure. With film that's not strictly true as you get to extremes — see this question on reciprocity failure. But for digital, it's not meaningfully a factor.


dslr - Spilt Isopropyl alcohol on camera, now it doesn't turn on


I have 99.5% Isopropanol that I am using for cleaning electronics and optics(I specifically ordered it from my local electronics specialist; it is no knock-off, it is genuine pure IPA for a ton of money).


I was cleaning my Pentax K5 mirror with it when I accidentally spilled some inside. Not much: not more than 50ml. Now the camera won't turn on. This is odd, since IPA should not be conductive. Is there some moisture sensor inside preventing it from turning on? I bathed my laptop in it last week (when cleaning the monitor) while it was on and nothing happened.


But the camera won't turn on!




Thursday, 13 October 2016

metadata - How can I incrementally date photos?


I have a collection of photos that have no date information. They have no Exif data, and the file modification dates are all identical. The only sequence is in the file name: image-0001.jpg, image-0002.jpg, etc.


Now I want to assign a date to these files (preferably in Exif) that are all 10 seconds apart. I'm not so interested in what exactly the base date and time will be, just that they all increment 10 seconds. So the first image will get 0:00:00, the second 0:00:10, the third 0:00:20, etc.



Is this possible with ExifTool, or other Windows applications? We're talking about several thousands of images, so doing this manually is out of the question ;-)



Answer



There's already a similar question on the ExifTool forums. It can be done using two sequential ExifTool commands. First, make sure all the date to the same


exiftool -datetimeoriginal="2015:02:22 00:00:00" DIR

And then increment the time on each


exiftool '-datetimeoriginal+<0:0:${filesequence}0' DIR

equipment recommendation - What lenses are best for food photography?


What lenses are best for taking photos of cooked dishes?


In some articles, I have read that I can have great results with lenses f/1.4 because they are cheap and they give that nice blurred background.


Others have great result with macro lens, but these are quite more expensive.


How different the results would look?



Would the ones with macro lens look so much more professional that I should not even consider the f/1.4 ones?


Are macro lenses good only for very close distances? What the maximum distance away from the dish that it can be? Is it good only for cropped images?


edit: I rephrased my question to make it more clear.



Answer



As a point to consider - recently, CreativeLIVE had a weekend workshop on food photography w/ famous photog Penny De-Los Santos. She used mainly the 24-105mm f4L and 70-200mm f/2.8 on an EOS 5DmkII (full frame) camera during the workshop. You can see the full gear list here.


That said, when shooting food the studio style, you have control on most of the parameters. If shooting with a long lens from a relatively close range, then your DoF will be shallow even with moderately fast apertures (i.e., you don't have to go all the way down to f/1.4 or f/2.8 to frame a bowl of soup nicely).


Update: "Are macro lenses good only for very close distances? What the maximum distance away from the dish that it can be? Is it good only for cropped images?"


Macro lenses are usually good wherever their non-macro parallels are useful. You just get, in addition, the ability to get really close to the subject for some 1:1 magnification. Their maximum focusing distance (MFD) is infinity (except for some very specialized macros). I can't imagine a special need for macro when shooting a whole dish, but it can get useful if you want to shoot seeds, crumbs or other very small food elements.


Wednesday, 12 October 2016

lens - Why do Full Frame lenses and crop body lenses exhibit the same crop factor when used on a crop body camera?


I have a Canon 7D, which has a crop factor of 1.6x.


When using a Canon EF-S lens I get the focal length stated on the lens, when using a Canon EF lens I get the focal length times 1.6 when used on the APS-C body. At least that's what I thought.


I just compared two lenses:




  • Canon EF-S 15-85mm f3.5-5.6

  • Canon EF 70-200mm f4


I took the same photo as you can see here.


The top photo is shot with the 15-85, the bottom photo with the 70-200 - both lenses are set to 70mm. Now why do they look the same?


I thought I would get 112-320mm (70mm*1.6 crop factor). What did I misunderstand about the crop factor calculation? Lightroom also displays the photos as having "70mm" and not 112mm.



Answer



Whether a lens is an EF or an EF-S lens, the actual focal length is always used. There are certain technical reasons why this is so, but the simplest is that a lens' focal length is defined as the distance from the film plane needed when the lens is focused at infinity to cast point light sources as a single point on the film plane. This doesn't change with regard to sensor size. What does change with regard to sensor size is the angle of view or field of view (FoV) that a lens of a specific focal length will include in the part of the image circle that falls on the sensor.


What this means is that if you are using a 70mm lens on a Full Frame camera, the FoV will be about 34° diagonally. The same 70mm lens on a crop sensor body will have an FoV of about 21°. That is an equivalent FoV of about a 110mm lens on the FF body, and that is why camera manufacturers say that the 70mm lens on a crop body is a 110mm equivalent. If you print photos taken of the same subject from the same distance using the same focal length lens with both cameras on the same size paper, the image from the crop sensor camera will make the subject appear larger. This is because the ratio between the crop sensor size and the print size is greater than the ratio between the larger full frame sensor and the same print size, thus the magnification factor of the photo taken with the crop sensor body is higher.



If you take both images shot at 70mm on your 7D with an EF 70-200mm f/4L and an EF-S 15-85mm f/3.5-5.6 IS they will have the same FoV because both lenses are set at 70mm. To understand the 35mm equivalent FoV they yield, both lenses need to be multiplied by the crop factor, even though one of the lenses does not project a light circle large enough to fill a full frame sensor.


astrophotography - What lens characteristics are important in star photography?


In optimal world I would buy a lens that is good in every way. But I'm on a budget and have to find a balance in quality and price. I'm looking for a lens for star photography, so in my case it will be a wide angle lens with good characteristics for capturing points of light in a dark sky. What would those characteristics be?


So far I've learned about coma, which seems like a thing to note when comparing different lenses for star photography. It would be quite disappointing if stars turned into long teardrops on the edges of a photograph even when every precaution was taken to make all stars sharp round points of light.


Vignetting would be an example of lens characteristic not so important in this use.


Many characteristics of a lens turn better when aperture is slightly stopped down, but I suppose I'd be wanting to use a lens with wide open aperture when trying to capture the stars in a dark night sky.


I'm not asking for lens recommendations. But, as an example of what kind of lenses I've been looking at, I name Samyang 14 mm f/2.8 UMC manual focus lens. Its price level is $350'ish in Amazon and seems to run with name Rokinon too. It seems to be reasonably sharp even when wide open - my camera is an APS-C sensor camera.



Answer




It is probably easier to talk about what qualities in a lens that often add significant cost that you don't need in order to do astrophotography.




  • The first is Auto Focus. Stars are such tiny points of light that the accuracy of most AF systems is not quite good enough to resolve them to the absolute sharpest capability of the lens. Most AF systems can't focus in the dim light of a starry night anyway. Even the moon, which most AF systems can attempt to focus sharply, needs a slightly different adjustment than the stars. The good news is that once you get your lens properly manually focused on the stars, it will stay properly focused as long as the temperature stays the same. If the temperature changes drastically, you may need to refocus as different materials in the lens will expand and contract at different rates.




  • The second is Image Stabilization, at least the electronic kind. To do any remotely serious astrophotography, you'll need your camera mounted on a stable mount such as a sturdy tripod. For some types of astrophotography a telescope mount with a sidereal clock drive that synchronizes the motion of the mount to the apparent motion of the stars as the Earth rotates on its axis beneath them is even better.




  • As you have indicated in your question, vignetting is an issue that can easily be dealt with in post processing, so a lens with little or no vignetting when wide open is not necessary for astrophotography.





The one attribute that is absolutely vital for doing astrophotography is acutance. This is the combination of sharpness and contrast that allows clear separation of the dark background and the points of the light of stars. Chromatic aberration can also affect acutance, and ideally a lens for astrophotography will demonstrate minimal CA. Chromatic aberration can be dealt with in post processing, but for it to be effective a detailed lens/camera profile needs to be applied. Most lenses with a comprehensive profile available for a tool such as Canon's Digital Lens Optimization contained in their Digital Photo Professional will be higher end lenses which also have most of the features listed above (and the additional cost) that you don't need for astrophotography. Like many thing related to photography, it is easier to get it right in camera than worry about chromatic aberration in post.


Assuming you want to do wide field astrophotography, you are on the right track with a lens such as the Samyang/Bower/Rokinon/Pro-Optic/Walimex/(and whatever else it is called this week) 14mm f/2.8. But be aware not all astrophotography is concerned with wider angles of view. It is, however, a good place to start if on a tight budget.


metadata - Software for editing EXIF data


Can someone please recommend software that enables editing for exposure mode EXIF data?


I have tried with Picasa, but it doesn't support editing of this specific property.



Answer



Jhead is a capable tool for modifying and examining exif data. See this link


Tuesday, 11 October 2016

lens - Why does fungus form in lenses, and how to get rid of it?


Recently I was using an old Pentax 50mm f/2 that had a quite big green spot, and later I was informed that it was a fungus.



A couple of questions raised from this:



  1. Why does fungus form inside the lenses? What kind of "food" does it find in a glass element?

  2. How does it form? Due to condensation? Due to bad storage?

  3. Does it have any impact in the final image? Some scratches in a lens will probably not appear in the image because to they will be very out of focus. Is this also true for fungus?

  4. Finally, when a lens is "fungused": How do you get rid of it?




What to do about mold/fungus in a camera lens?


by Yuttadhammo



I am living in a tropical country where humidity is pretty high. I never thought it would be possible that something could grow inside a lens, so I haven't been so careful with my canon camcorder. Now I see there is a white spore growing on the inside of the camera lens (see photo below). Is there any way, short of finding a camera shop (doubtful there are any in the country that can handle this), to remove this?


The spore is the white dot in the centre (it's opaque), and the dusty patch on the right of the lens is also on the inside, must be the same stuff.


fungus spore on lens



Answer



For all the following: YMMV*, caveat emptor, no responsibility taken for advice given, you decide whether to try this at home. It may even work :-). Be aware that damage may already be fatal and/or that fatal (to the lens) damage may occur along the way. Best attitude is to regard the lens as a writeoff now, with anything you can gain from it by the methods below being a bonus.


Fungus in a lens will always degrade the image but the amount of degradation may be invisible to mere mortals or may make the lens completely unusable by any standards. Often even a very visually significant lens defect - such as a chip or scratch, will not be instantly obvious in final images to a casual observer. Experts will usually be able to detect almost any defect (or say they can - mere mortals will not be able to tell if they are correct :-) ). Also, lens settings will affect how much a given defect affects a given image.


In some cases the advice given in 1a and 1b below will transform results from generally unacceptable to generally acceptable. In other cases they won't. Only trying it will tell you how good a method will be.


The best advice (but too late :-( ) is to never let it happen. Fungus only grows in moist conditions. Keep your lenses in a well ventilated dry location with dessicant sachets. However -


If it's inside the lens there are two options (apart from disposal). Unfortunately, while either may work, neither is certain to work well.





  • 1(a) Shining UV (ultraviolet) light into the lens for an extended period will "discourage" the fungus, how well and how long is uncertain. Simply leaving a lens with iris fully open on a sun facing window ledge in a dry location for weeks to months may produce good results. Cap lens at rear, and tilt so that sun shines into lens during sunnier parts of each day. (Be ware that sun shining directly along the axis of the lens or close to it may focus light onto end cap and melt it - unlikely but check point and degree of focus.) I tried this procedure with an extremely old Minolta 50mm f1:1.4? manual lens and achieved tolerable results. I simply left the lens as above for many months and when I next looked found that mold presence had been very substantially reduced.


    1(b) Light from a germicidal (short wavelength) UV lamp may be used in place of sunlight. This sort of light can blind you or damage your eyes permanently if looked at for substantial periods and can cause "arc eye" - painful but usually temporary inflammation of the eye. This does not mean you should not use such lights at all - simply that they need to be used with due respect. These lights are available from many sources for many purposes and can be very low cost.


    Note that "black light" UV light is not suitable for this purpose. It is longer wavelength and not very biologically active.


    Note also that the short wavelength high energy UV (which is why you are using it) from germicidal UV lamps will also degrade other materials such as some plastics and miscellaneous other material - including, possibly, parts of a plastic lens housing. This depends on material, distance, light energy and exposure time. YMMV but caveat emptor - ie know that you are using a tool with sharp unguarded blades (even though you can't see them) and use with due caution.


    All the above may put some people off UV germicidal lamps. If so, that's good. They are a great and useful tool but not suitable for use by careless or unthinking people.




  • 2 . Dismantle and clean. If the lens is so degraded that it is unusable and if the method above does not work well enough then the lens must be dismantled. If the lens is otherwise a 'writeoff" and you are competent mechanically you may wish to try this yourself. Reassembly of a lens capsule is considered to be an expert task and realignment on reassembly may require arcane knowledge. This is why qualified lens servicing people are still in business and cost money to use.


    Fungus often attacks lens surface coatings and may etch the glass itself so the lens may be noticeably or fatally degraded regardless. How much the may/may/may applied in your case is tbd. Some lens cleaning works very well indeed. An aficionado and a good MTR test will probably tell you that something has happened but the results may be very tolerable in practice.



    You will find articles on the internet on lens cleaning methods. I read a paper by either Zeiss or Leitz that suggested that cigarette ash makes an excellent fine cleaning compound (!!!).








  • YMMV - Your mileage may vary.




  • Caveat emptor - let the buyer beware = you are on your own.







Added: Member 19602 made this comment - as he has left and comments may too I'm adding it to my answer.


On April 7th 2013, once was member 19602 said:



  • I can tell you with absolute certainty that the Leitz recommendation is not a sealed container with desiccant but an area with constant air circulation. I used to be with Leitz Germany.


Why is the front element of a telephoto lens larger than a wide angle lens?

A wide angle lens has a wide angle of view, therefore it would make sense that the front of the lens would also be wide. A telephoto lens ha...