Is there a dynamic-range reduction device (preferably passive, optical)?

When processing sound, one can use a Compressor to reduce the dynamic (DR) range of the signal. In photography, we often run into the problem of scenes with DR larger than the sensor's capture ability. For example, shooting a person on a white snow background. This leads to either the subject is underexposed, the snow is overexposed or both.

A Neutral Density filter is used to reduce the amount of light received by the sensor. However, a uniform filter does not (theoretically) reduce scene DR. Graduated ND filter can be helpful in some cases, but the use is very specific.

Is there a device (material) that can reduce the received DR? Preferably, a passive device (like a lens filter)?

Obviously, in the sound compressor example above, the DR of the signal chain has to be able to accommodate the original DR in order to prevent unwanted clipping and distortion. In Digital Photography, this is equivalent to a high DR sensor, and the compression itself is equivalent to HDR tone mapping.

Answer

Tiffen has a line of contast-modifying filters that were developed for this purpose. In 1992, they received a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences for the development of the filters.

sensor - Is "Ultrapixels" just marketing or is there a real benefit?

HTC has branded the sensor in its new phone (the HTC One) to be "Ultra pixels". For the same sensor size it only gives you 4MP where today's standard for top of the line smartphones is 8MP and up. Of course this may have benefits in low light conditions, but I am wondering whether the exact same effect could not be replicated by setting the 8MP camera to take a 4MP photo ?

Is the term "Ultra Pixels" just masking the fact, that I do not have the option to take higher resolution photos in well lit conditions ?

point and shoot - What is a Carl Zeiss lens in a camera?

I have a Sony CyberShot camera and I don't know why they use a lens in the camera. What is a Carl Zeiss lens?

Answer

A lens is needed to focus light on imaging sensor. For example, here's an image taken without lens attached to camera:

For comparison, same scene taken with a lens attached:

Carl Zeiss is a German manufacturer well known for carefully designed good quality optics; see also what makes a Carl Zeiss lens so special in a smartphone (the reasons are similar for a pocket camera).

printing - How well do dye-sublimation printers perform with black & white pictures?

Most of the dye-sublimation cassettes have CMYO (= cyan, magenta, yellow, overlay) panels.
Are there any cassettes designed specifically for black & white pictures?
For example (and as jrista pointed out), some modern inkjet printers have additional black and gray inks to help to produce more accurate grayscale tonality — could there be like black, gray, light gray & overlay cassettes?

If not, how is the black & white performance with a regular CMYO cassette? Do some cassettes tend to tint the black & white picture towards to some colour?
Are there any example scans around the web, so I could judge by myself?

Or would I get better results with a modern inkjet (photo) printer? (I'd also like to see how they compare.)

I'm having a hard time finding up-to-date information via Google. wallyk's answer gave some clues, but as the comparison is from 2005, and (hopefully) both dye-sublimation and inkjet printing technologies have advanced, it could be taken as a rough estimate or merely as a starting point.

Answer

It seems that for e.g. Canon Selphy ES -line BWO (black, white, overcoating) cassettes are available. Also some fancy CMYO+Gold and CMYO+Silver options exist.

It should be noted that those cassettes aren't available for the Canon Selphy CP -line of dye-sub printers — but you've probably noticed that already, haven't you.

And what comes to your question about adding additional gray inks to achieve more accurate grayscale tonality: it is not necessary. Dye-sublimation prints are not dithered and every panel in the cassette is used only once for a print, so additional gray panels wouldn't add anything to the print other than cost. At least in theory, as midlevels could ease the calibration.

Sadly, I haven't found any scanned examples of B&W dye-sub prints via Google neither up-to-date comparisons to inkjet prints. Those would be interesting to see, though. Not to mention that it would be interesting to see how white is the white-dye. (I didn't find any detailed specifications on the BWO-cassette, so I can't be 100% sure are the grays achieved by altering black levels or mixing black dye with white dye. Selphy ES40's manual states the ink type as "BW".)

What are the different Canon tripod mount ring types for?

What are the types of Canon's tripod mount rings? I've heard about A, B, C and D types, but have no idea what it means or what the difference between them is.

Answer

The different types are:

• Tripod Mount Ring A (W) or A II (W) [hinge] for 70-200mm f/4 L (for both IS & non-IS versions), 300mm f/4 L, 400mm f/5.6 L,


• Tripod Mount Ring A (B) or A II (B)[hinge] for 200mm f/2.8 L, 200mm f/2.8 L II, 80-200mm 2.8 L


• Tripod Mount Ring B (W) [no hinge] for 70-200mm f/2.8 L (IS, non-IS, IS II), 100-400mm f4.5-5.6 L, 300mm f/4 L IS


• Tripod Mount Ring B (B) [no hinge*] for 100mm f/2.8 Macro, 180mm f/3.5 L Macro & MP-E 65mm f/2.8 Macro


• Tripod Mount Ring C (W) [hinge] for for 70-300mm f/4.5-5.6 L IS, 28-300mm f/3.5-5.6 L IS



• Tripod Mount Ring D [hinge] for 100mm F2.8 L IS Macro Lens

The interior ring dimension for each are (note well they do not go "in order"):

• Tripod Mount Ring A 65-66mm


• Tripod Mount Ring B 78mm


• Tripod Mount Ring C 82mm


• Tripod Mount Ring D 68-72mm

Most have (B) and (W) markings on them, meaning Black and White respectively. A and A II are interchangeable.

Most Canon rings have a hinge that allows the collar to be removed without dismounting the lens. Only Canon "B" rings do not have a hinge and do require the lens to be dismounted to remove the ring. 3rd party rings come in both hinged and hinge-less designs. Some users prefer the hinge-less version for ease of use when using the lens collar to transition from landscape to portrait orientation. Other users prefer the ability provided by the hinge to add/remove the collar without dismounting the lens.

Lenses that use the Tripod Mount Ring B (W) have lugs that fit inside a grove in the lens collar. The collar also has slots to allow clearance for the lugs when the collar is removed.

*The Tripod Mount Ring B (B) pictured at Canon's online store appears to have a hinge. This is in fact an incorrect picture of a 3rd party Tripod Mount Ring. (you can read "for Canon" on the mount) The Tripod Mount Ring B (B) pictured at B&H is clearly marked correctly and is not hinged and does include the slots and groove for the lugs on the lenses that include the Tripod Mount Ring B (W) as standard equipment. The only lens that uses the Tripod Mount Ring B (B) not supplied with the collar as standard equipment is the EF 100mm f/2.8 Macro (non-L) which does not have lugs that fit in the slots and groove. There is a plastic adapter included with the B(B) ring that fits the EF100mm 2.8 USM Macro lens for use with the B(B) ring.

curation - I've 'lost' a photo. I know I have it but I don't know where — how can I find it?

A friend has requested a full-res copy of a photo I posted on Facebook a few years ago. Back then I just had a point and shoot, I didn't organize my photos well, and since I have started organizing photos, it's only the newer ones that are organized. So somewhere in the mess of folders on my drive is this photo, what's the best way to find it (amongst tens of thousands of photos)? Is there a Tineye-like program I can download and run on my machine?

Answer

The people who make TinEye have a product called PixMatch which can search individual collections. It's not implemented as a desktop application, though — it's a server-based API. And it appears to be priced for serious enterprise use, not for individuals. So that's there, but not really an answer.

But a competing company does have something for the desktop — Imense Desktop Similar Image Search, which runs on Apple Mac OS or Microsoft Windows with Adobe Bridge CS4. It's free for collections of up to 4000, and seems reasonably priced above that.

There are, in fact, a ton of things, once I figured out what to search for: Content-based image retrieval. There is actually a lot of work in this area, and a ton of both open source and closed tools. Most of these are focused on the big-enterprise/academia side of things, and are in various states of completion and polish.

Of these, I think imgSeek is the most interesting for the desktop case. This is Python/QT-based and so in theory should run on pretty much any platform, but is focused on Linux. It does a comparisons based on metadata (date, time, etc.), simple features like average luminosity or color, or by sophisticated wavelet-based estimation of similarity. That's probably overkill for finding the exact same image in a different size with different compression, but should work really well since that's basically the easiest possible case. It'll also find near matches, like this:

All that may be too much work for this specific one-time problem. How are your not-organized photos stored? Even if their filenames aren't helpul, the EXIF metadata should still be good. One simple approach is to import them into a program which can examine this data and search or sort by it. Or, you could use a program like jhead to rename them all so they have sensible date-based names. (Maybe both.)

autofocus - What does infinity focus mean and when should I use it?

All my lens have focus ring where at the end there's an infinity symbol. What does that mean? If I'm taking landscape shot and what everything from near to far to be in focus, do I use infinity? Or am I better of focusing onto a single point one third up from the bottom (I've read that, that's the rule of thumb).

Also, why is infinity a range on most lens. It's never a single point.

How can I take wide angle macro photos with a Nikon APS-C camera?

I am looking for wide angle macro solutions for Nikon APS-C cameras to create images similar to these. By "wide angle" I mean 20 mm (30 mm equiv.) or wider, and by "macro" I'm hoping to get close to 0.5× (not sure it will be possible).

My main concern is that simply adding even a thin extension tube will make it impossible to focus (by placing the plane of sharp focus behind the front element). I'm also worried that with some thin extension tubes I'd lose aperture control with G lenses.

What I'm looking for is either: 1. Confirmed working solutions (i.e. specific lens + specific extension tube; is there something that works with the 18-55 mm at 18 mm?); 2. Or alternative, non-extension tube based solutions.

Answer

I use a Nikon mount Sigma 15mm (22.5mm equiv) f2.8 lens which focuses to within 3cm to 4cm in front of the lens on a DX camera. Stopped down to f11 or f16 there is considerable depth of field.

Paul Harcout Davies and Clay Bolt have written an eBook on the subject of "Wide Angle Macro Photography.

This link points to an article on Wide Angle Macro http://www.imaging-resource.com/news/2013/07/16/wide-angle-macro-photography-close-ups-with-impact-part-1

powershot - Can I get the Canon hacker development kit to work for a camera that has no official CHDK builds?

I tried to find a matching CHDK version for my Canon PowerShot SX540 HS.

The tool ACID tells me:

No official builds are available for this camera

See

What could I do to get CHDK working on this camera?

film - How did they post process before Photoshop?

So, yes, I'm intrigued as to how they post process pictures before Photoshop (or computers, for that matter) came about. Or is post processing a by-product of the computer revolution?

My understanding of film photography (all from the film equivalent of a point-and-shoot we had when I was a kid) is that light burns into film then film gets developed. And, well, unlike bits, your end-product is tangible and "permanent", for lack of better term.

I'm woefully ignorant about film processing but I guess this is where the post-processing takes place? How do they tweak color temperatures? Remove red eyes? Retouch skin blemishes? Do they use special dyes/inks to achieve better colors/contrast?

Answer

There was quite a lot you could do, actually.

Let's start with the basics -- overall exposure and contrast. This is something that anybody who had a darkroom would have done as a matter of course. Photo papers come in different contrast grades, and some black-and-white papers were variable contrast, reacting differently depending on the colour of the light you used in your enlarger. You could do a lot about changing the overall exposure and contrast merely by changing the time that the paper was exposed and the contrast grade of the paper. Changing colour temperature in colour prints was a matter of changing the filter pack (or the settings on a dichroic light source). Small shops would go by a keen eye; large labs would use a colorimeter.

Photoshop (and similar programs) have tools called "dodge" and "burn", and these come straight from the darkroom. You would use a shield to "dodge" light from hitting the paper, or a larger card (often with a hole in it) to let extra light "burn" the paper. This would let you make local contrast and brightness changes.

"Masking", including "unsharp masking" also comes from the darkroom. Contrast masking would be done by sandwiching your negative together with a piece of unexposed film (usually something with a very low sensitivity) and exposing the film through your negative. That made a weak positive image, which you would then develop with low contrast. Sandwich the two together again, and your shadow areas got some extra density, bringing the overall contrast down. Put a piece of clear film between the two when exposing the mask, and you get an unsharp mask, which could be used to enhance the edges in the image (the same way that the Photoshop effect works). You could also paint directly on the mask or bleach out exposed areas in order to remove areas of the image.

Retouching involved using pencils or dyes on both the negative and the print. Since you can only controllably add density (you can put more black or colour on a little at a time, but bleaching is more-or-less an all-or-nothing technique), you would lighten areas by retouching the negative and darken them by retouching the print. Red eye correction was usually done on a print using a cyan dye pen and a careful dotting technique. It was all hand work, and it was enough of an extra-cost option that most people wouldn't have bothered with it for their snapshots.

Then there were wholesale changes you'd make by airbrushing and collage. That was normally done at a very large size and then rephotographed to minimize the appearance of the handiwork.

Add hand-tinting black and white pictures, using ortho/litho film to transform a continuous tone image into line art or bas relief and so forth, and the arsenal of tools and techniques gets pretty big. It was nowhere near as easy as Photoshop, and there wasn't so much an "undo" as a "start all over again", but we weren't stuck with what you could get at the druggist's by any means.

light - How do you avoid a dim portrait with a bright background and no external flash?

I took a picture once in a beautiful location with an awesome background, and a cool location to get the shot. The problem is, the location of the subject had substantially less light then the background, giving a silhouette effect. Without using an external flash, and on a low budget, what could I do to improve this picture?

Specifically, I shooting with a DSLR, outdoors. The DSLR has a small pop-up flash. The nearest good light source was maybe 5-10 feet away.

Thanks guys!

---

How do I avoid a dark subject when there's bright sunlight from windows?

by Franci

I recently shot some photos at a friend's wedding. The location was lovely with lots of light — sometimes too much. The sunlight from the windows and skylights seemed to overpower the shot and the subject/people were very dark. What are some ways to avoid this without using fancy equipment? (I'm just starting out, I'm not a wedding photographer or anything!)

Here is one example I took — and this is after I've lightened it somewhat with Picasa:

I'm using a Nikon D5000 with a standard 18-55mm lens.

Answer

Metering from the background as rfusca suggests may not give you the results you desire - the background will likely be very overexposed spoiling the beautiful location.

One solution to that problem is to shoot two exposures and merge them. One exposure is optimal for your subject and one optimal for the background. If your subject remains relatively still merging them is not too difficult and there is a wide variety of software available to do this. Google "HDR" if unsure! One problem with this method is that if the background is significantly brighter than the subject then the shot exposed for the subject may have lens flare or other defects due to the strong backlight.

However it's better to do it in one go if you can so I would say if you have no external flash then use the internal one! It may produce harsher shadows due to the position. The best way to avoid this is to diffuse (spread out) the light, using a sheet of paper, white t-shirt, whatever is at hand.

edit: che's suggestion of a reflector is a good option for the case when the sun is in the wrong direction, it's worth noting that it wont work if you're in a large shadow area, you need a line of sight to the sun.

exposure - Why is my camera metering indoor scenes as darker than I expect, forcing me to use a high ISO?

I am shooting in natural light, with my subject facing a full floor-to-ceiling south facing window. You would think my meter would allow ISO between 200-400 in bright light, but I was lucky to get it to 640, with f/3.2 and 1/60 (manual mode).

I've read other places that people say put your ISO down to 100 for indoor shots for greatest clarity (especially sharp eyes) — but don't know how I can with subjects potentially moving. Is there a setting in my camera (Canon 5D Mark III) I am missing, or something that might be making my meter need more light?

portrait - How does one best deal with shaded faces in bright sunlight?

When photographing people in bright sunlight, parts of faces are often shaded by hats or by their own contours. This creates highly-contrasted faces, and either a very bright background or very dark faces.

Using flash doesn't always help, especially when photographing a large group (~10 people) from a little distance.

What's your solution for this common situation?

Answer

For me, I have reflectors which can be positioned (sometimes with help) so as to fill in the light on the subjects. There are some reasonable 5-in-1 options out there, I have a 43" version of one of them and it works very well, folding up to a pretty small package and giving lots of options for cooling or warming the light as needed.

If you don't have reflectors, but do have larger, bright, surfaces you use, then that too is an option. What it really boils down to is getting some of generally available light redirected to the place you want it and, for that, many reasonably reflective items will help a great deal if sufficiently large. Heck, it can even by some bristol board or shiny wrapping paper, I've done both.

Anyways, those are what I do and, to be honest, I prefer that sort of light over a flash anyways. Fill flash can harsh, especially when it is on camera, and so I prefer to avoid it.

focal length - How to estimate camera sensor size?

I am using a smartphone for capturing photos and I need to estimate the camera sensor size (mm*mm). I have the resolution (in pixels) and the focal length (in pixels). I can also measure the size of any stationary object and its distance w.r.t the lens. Basically, I don't have a pixel-to-mm metric for any of the above parameters that I can use. Is there any way I can calculate that to estimate sensor size?

software - How can I recover deleted photos from an SD Card?

My technophobe mother returned from a European trip to discover she'd erased all but 15 images from a nearly full 2GB card. As I am the computer guy in the family, she posted the card to me and asked that I make something magical happen.

The photos were taken with and deleted by a Nikon Coolpix. (I don't know the model.)

I am a Linux guy, but there is a Windows Vista box at my disposal.

What is my best strategy to try to recover something?

digital - What do all the settings do in Lightroom?

What do all the do all the develop settings mean in Lightroom?

For example, what does the Fill light setting do, and how does this differ from the Brightness setting?

I can of course just play around with the settings and see what the effect is, but I've found that I get better results when I stick to the settings that I understand the theory behind (such as Exposure and White Balance).

Why does using my slave flash darken the image?

Why does my slave flash at full power actually seem to darken the image?

The camera (Lumix G1) is set to M-Mode, forced flash at -2, f6, 1/30s. I set my external flash (Nissin Di466 FT) to slave mode "S2" to ignore the first "measure" flash.

I do an experiment with three shots:

1) Slave flash off: Image is medium bright.

2) Slave flash +0.5: Image is brighter

3) Slave flash +1.5: Image is really dark with a red tone

How can this be? Even if the slave flash has missed the right point in time, image 3 should still have the same brightness like image 1, since the camera flash is still on. Am I missing something?

(iExposure is off, and ISO is set to 200).

[Edit: it turned out that on the Di466 "S2" is the mode that does NOT ignore the pre-flash. But I still do not understand the behavior.]

Answer

You guys are on the right track. Here's what's happening in each picture:

Slave flash off.

• Your camera fires a pre-flash


• The camera determines how much flash power it needs for proper exposure based on how bright the return flash is.


• The shutter opens, and the camera fires its flash at the power level it just determined.

You get a medium-bright picture.

Slave flash at +0.5

• Your camera fires a pre-flash, which triggers the slave flash.



• The camera sees a very bright return flash, so it decides to use very low power on-camera flash for the exposure.


• The shutter opens, and the camera fires its flash at a very low power, which triggers the slave flash again. At only +0.5 power, the slave flash still has enough charge to fire again immediately.

Although the on-camera flash was very dim, the slave is much brighter than is needed for proper exposure, so the picture is overexposed.

Slave flash at +1.5:

• Your camera fires a pre-flash, which triggers the slave flash.


• The camera sees a very bright return flash, so it decides to use very low power on-camera flash for the exposure.


• The shutter opens, and the camera fires its flash at a very low power. However, the slave flash, at +1.5 power, has already used more than half of the charge in its capacitors, so it can't fire again immediately.

Since the on-camera flash is dim, and the slave doesn't fire while the shutter is open, this picture is darker, and only consists of ambient light. Since your camera thought the scene was going to be lit mostly by flash, it balanced for xenon light. The ambient light (which is probably tungsten or tungsten-colored CFLs) is a much lower color temperature than xenon, so your picture has a red tint.

photoshop - How can I get the best quality prints from an iPhone photo?

I have a photo on my iPhone that I'd like to print, but the quality is poor. Is there anything I can do so that I can print it?

I have Photoshop CS5.

How to correctly expose when using a flash?

I have been using the Manual mode ever since I picked up my Nikon D3200 about 6 months ago. I am pretty well versed with the exposure triangle & how to use it.

However, recently - I am starting to discover flash as a non-evil thing. And reading the theory about it, has left me confused.

Everywhere I read, people always say...

Situation : subject is facing camera with sun in the background (bright background, dim foreground)

1. First expose properly for the ambient/background


2. Then expose for the subject/foreground

What does this really means? Should I select a focus point on background, adjust my exposure & then focus on my subject again & then adjust the flash compensation to adjust for proper exposure? (this might mean multiple photographs till I find perfect exposure).

It would be great if people who are well versed with flash photography could answer this for me.

Thanks,

digital - What's the difference between CCD and CMOS image sensors?

I keep reading articles about CCD vs CMOS image sensors. What is the difference between these two types? What exactly do these sensors do in terms of photography?

Is a CCD-based camera going to be able to compete in the future? If I buy one, can I count on using it for some years or would it be better to upgrade to a camera with a CMOS based sensor?

image quality - Is there a set of common criteria for evaluation of photographs?

Is there any set of criteria for evaluating a single picture that is in common use?

I have the following situation: I want to write down my criteria on how I rate my pictures. At the moment I give stars from 0 to 5 to my images but I just do so as I please. However, I thought it would be good to write down how I've done it, so that I get reasonably consistent results.

I am thinking of writing something down like:

1. ★ In focus, exposure makes subject visible. Basically, I have rated this image and it is okay.


2. ★★ Nice picture, subject has a nice expression on face (if human, etc.)


3. ★★★ Technically correct picture, very publishable.

But isn't there something like I am thinking to codify already out there? For example it might be used by professional reviewers in competition or stock photography.

Answer

I am certain there are no such generally-accepted criteria, because there are too many variable factors. Even technical aspects of image quality are subjective, and one person's "too much blur" may be another's "sense of motion".

I'm sure many specific contests have their own scoring systems and scoring rules, to help with consistency across years and between judges, but I don't think I'd want to apply those rules to my work, because my goals would be different from the goals of the contest.

The Professional Photographers of America association gives twelve elements for judging images for their annual exhibition. These range from "technical excellence" to "lighting" and "color balance" to "story telling" and "creativity". You might find these useful, but it's not really a simple star scale. I can imagine applying some sort of weighted score to each, generating a final number, and boiling that down to stars, but I think the particular weights would be a matter of endless debate.

What does it mean if the main peak of my Histogram is beyond the top of the chart?

I tried reading this thread about histograms, but couldn't understand it well enough to answer this question.

I took some shots yesterday where the main peak of my Histogram was actually off the chart. The histogram had one large peak and most everything else was very low. What exactly does this mean, and if it's something bad (I expect that it is) how can I avoid this in the future?

Here is the Histogram in question :

and the image can be found here. (Update: I altered the photo, so the link is taking into account Jrista's excellent suggestions. This histogram no longer corresponds to this photo.)

Answer

The height of each individual, vertical line in a histogram indicates how much of that particular tone your image has, or the tones intensity. As tones in a histogram progress from left (black and shades) to right (brights and highlights), where a particular vertical line lies indicates how intense the tones represented by that line are.

If one particular tone is extremely intense, and the rest are very low, then the image is primarily comprised of that (or those) particular tones. Generally, this happens in the highlights when they get blown out. It it happens somewhere else, then the histogram is simply telling you that your image is almost entirely composed of that particular range of tones.

It should be noted that the histogram generally does not show enough vertical lines to represent the entire tonal range of an image. Every individual vertical line in a histogram usually represents a small range of tones.

equipment recommendation - What's the difference between the levels of weather sealing on DSLRs (e.g. 50D vs 7D vs 5D vs 1D)?

My Canon 450D can (or at least has) survived light rain, condensation in the cold and a little icing up overnight during astrophotography...

The various different levels of camera above the Rebel/XXXD range talk about improved weather sealing, and of course the L lenses do too... but I've never seen an indication of exactly "how sealed" they are. People talk about the 1D/5D having better sealing than the 7D which is in turn better than XXD series, and that the Rebel/XXXD series just don't have it (though obviously the plastic shell offers some basic protection). But what's the difference?

In short, what is the quantitative difference between the weather sealing on a 50D vs 7D vs 5D vs 1D?

I'm referring to Canon models only due to familiarity with them, I'm pretty sure this all applies to any brand offering weather sealing.

There's a system called IP Ratings which define weather sealing against dust/moisture. Do weather-sealed DSLRs meet any of those criteria? By which I mean, does the manufacturer make IP rating claims? (It's all good and well to say "I once splashed water on my ... and it's fine" but that's no better than me getting ice/condensation all over my 450D and 10-22 and being lucky it still works fine).

Or is there some other specification which the different models meet? Ideally I'm after objective claims that can be made to differentiate between the levels of weather sealing (e.g. "safe in any level of rain", or "safe to submerse in water", or "safe on the beach/in a dust storm/...").

I'm not upgrading my camera body just yet, but plan to in a year or two and want to know if there's one that's going to be safer to use in some more extreme conditions, and whether I'll have a warranty after taking it there (;

Answer

I'm not aware of any specific claims for immersion, rain or dust resistance made for any SLRs. I've not read every warranty, but if there was even one that covered water damage I'd be surprised.

Weather sealing is typically a combination of high-tolerance, tight-fitting joints and gaskets. "Better" sealing essentially consists of more sealing in more places.

The closest thing I know of to objective data are renderings of weather sealing locations (courtesy dpreview.com):

_{(source: img-dpreview.com)}

_{(source: img-dpreview.com)}

_{(source: img-dpreview.com)}

As an aside, an interesting (though apocryphal) trick from the first Gulf War to keep dust off of cameras and film was to store them immersed them in water - the catch being you needed an a camera like the Nikonos, which is rated to something like 60m depth.

What should one consider when choosing a style of tripod head?

What should one consider when choosing a style of tripod head? There are ball heads, 3-way pan/tilt heads, geared heads, even gimbal heads.

I'm not asking so much about brands, but styles... how should one consider which type of tripod head will be best suited for their style of photography?

Answer

Your last sentence pretty much describes what you need to consider with tripod heads: what and how do you like to shoot.

As geared and gimbal heads are specialized, it's really between the pan-tilt and ball heads. Many start with pan/tilts due to relatively low costs, but will find themselves switching to the ball head for ease of use, and sturdier head (IMO ball heads offer a more sturdier mount than pan/tilts at the same price point--ie to get a sturdier pan/tilt you have to pay for a more heavy duty head).

3-way Pan/Tilt Head
With 3-way heads, your camera moves on 3 distinct axes (axissesis?). If you need precise movement on each axis for your needs (panning for sports for example), then a 3-way makes a lot of sense. It's downside is the need to adjust three knobs to set your camera position. Many start out with a Pan/Tilt head, because of the lower costs.

Ball Head
A ball head gives you less precise control of each axis, because your camera is mounted on a ball and socket joint, typically with two controls, one to lock the mount, and the other to adjust tension. You have less control, but are given more degrees of freedom to move your camera around, allowing you to more quickly adjust your camera with fewer controls to manipulate. Some ball heads allow for independently panning around the horizontal axes without manipulating the actual socket, but this is a feature, not a standard. This is probably the most general purpose type of tripod head, and many who start with budget pan/tilt heads move to ball heads for greater flexibility and sturdier mounting.

Geared Heads
A geared head is a type of head that uses a crank-shaft + gears to rotate the head. Typically found on 3-way heads, these heads allow you to rotate the head using a crank, rather than applying force to the camera body itself, resulting in smoother movement, and a finer grain of control over moving the camera body. Architecture, and any other application requiring a fine control over placing the camera make for good uses for geared heads.

Gimbal Head
Gimbal heads are specialized heads typically reserved for long telephoto lenses (400mm+). It gets it's name from a gimbal, a type of pivot support that allows movement on a single axis. Gimbal heads are designed to allow you to rotate heavy lenses about it's center of gravity, which results in easier movement. These are used in any application that uses huge telephotos, bird-in-flight, other wildlife, sports, etc.

What are these dark spots in my pictures?

I've been seeing these dark spots in my pictures. They appear a lot more on some pictures than others, but they are in the same place in the image and independent of the lens being used. Is this dust? I've also heard that you can get oil spots on the sensor.

The image is from a Nikon D7000.

diy - How can I make my own film scanner using a DSLR camera?

How can I make my own film scanner (35mm) using a 16MP DSLR camera?

For using the camera, I understand that I basically need a soft and even light source and a macro lens to focus on the films from close distance, all of these should be placed in a dark room or a dark box to avoid any unwanted light or reflection on my films.

Any ideas that how can get the best results?

Any DIY articles on how to make the whole setting? and what equipments do I need?

---

I can also use my normal CIS flatbed scanner, but I still have to make my own film adapter and light source for it. which one is better in your opinion, camera or normal scanner?

Answer

This is explained here but unless you really insist on building your own, I suggest you buy a slide-scanning attachment which is quite cheap.

In either case you need a close-focusing lens. If you have a macro lens, then use it. Otherwise you will have to get macro focusing using another macro technique such as extension tubes.

You will also need an even light source. The link above uses a flash which seems like overly complicated. Instead you can simply use a computer monitor showing pure white image over a large surface area. You can always adjust colors using WB and Fine-Tuning if your white is not exactly white.

technique - How can I make slit-scan photographs with a dSLR?

Surfing the web, I stumbled on an iPhone application to make slit-scan images. However, I have no intention of buying a smartphone.

How could one achieve similar results using a dSLR (preferably, but not necessarily, in-camera)?

Answer

Depending on what it is you want to photograph, producing a slit-scan image can either be trivial (done wholly in camera), or somewhat difficult (require various contraptions).

Most modern dslr's use a "rolling shutter" which in effect, emulates the slit-scan technique used by cinematographers.

The effect of which is very pronounced when using a dSLR that also shoots video. The so called "jello effect."

So, if you want to try making slit-scan photographs, you can take a photo of something fast (like an airplane propeller), or shake or throw the camera while taking the picture.

Otherwise, you'll need to set your dlsr on long exposure, and setup your own "slit" shutter.

Personally I'd just pony up for an iphone and buy the $1.99 app, rather than toss my camera around or build a shutter system ;)

equipment protection - How to protect lens from mist formation while shooting in places like beaches?

Usually when photographing cool breezy areas like beaches in the evening, I have experienced mist formation inside the lens. Once this mist formed, it stays there for at least an hour even after keeping the camera inside the bag.

How to protect the lens from these kind of mist formation? Is this really harmful for the lens?

Also what are the safe ways to get rid of the formed mist quickly?

flash - What Yongnuo wireless triggers work together?

Will a Yongnuo YN-622-TX operate a Yongnuo RF-605 attached to a remote YN-565EX flash, and will it allow the 622 to perform eTTL operability with the remote flash?

Also will the YN-622-TX operate a YN-560IV flash, albeit in manual mode?

How to make travel photography captivating, intriguing, thrilling?

When I travel I take photos of a variety of subjects like waterways, buildings, cultural events, the local people, landscapes, conveyances, nightlife, myself and my wife, things I see around me -- pretty typical stuff. I rarely plan for photographs. Instead I just take the best shots I know how at the moment that I want to record a memory or otherwise see something beautiful.

I know there are worse and better ways to compose shots (eg rule of thirds), better and worse ways to plan for and handle lighting conditions (eg magic hour), more and less interesting subjects (eg beautiful architecture).

What I'd like know is what recommendations do you have to make travel photos more compelling? How do you move from moderately interesting shots to something really engaging? Are there photo principles that apply especially to travelling? How do you increase the likelihood of catching something really special? Are there any recommendations on post-processing hundreds or thousands of different subjects?

Answer

The thing about travel is, you are someplace unique. The thing to do is figure out just what is unique about where you are, and try to capture some aspect of it that means something to you. For instance, in Amsterdam I saw bikes everywhere so I tried to get interesting shots involving bikes:

http://www.flickr.com/photos/kigiphoto/4165886056/in/set-72157622827849667/

The other thing to think about is that other people generally have an idea about what a place is. So you can either try to show something similar to what everyone knows a place is about, but with little twists - like this shot of the many buildings of Hong Kong across the water plus the famous sort of boat they have, I bought a flower from a street vendor and carried it around taking pictures:

http://www.flickr.com/photos/kigiphoto/5197306319/in/set-72157625391550866/

Which is a great way to meet people by the way. People love anyone with a flower!

Or, you can just try to go for the most nicely done canonical shot of the place you are at, so people are just excited to see a really good example of what they are expecting. For me Venice is canals and boats and I tried to find a nice atmospheric shot that would instantly say Venice to anyone viewing:

http://www.pbase.com/kgelner/image/80167194

I think it's also a good idea not to review too many images from the place you are about to travel to, so you don't get too stuck into thinking about getting a few particular kinds of photographs from a place.

What are the metal items on top of an older Nikon lens?

Does anybody knows what the two metal items on top of the lens are used for?

Answer

That's the metering fork, that was used to send information about the aperture setting from the lens to the camera on older camera models. The camera would have a pin that fits in the fork, so that turning the aperture ring moves the pin.

You can see some images of that at Useful Info: Nikon Lenses.

equipment recommendation - Is it worth buying an expensive CPL filter over an e-bay cheap one?

I have already got a circular polarizer filter (CPL) filter for my canon EF-S 18-55mm and it is working fine, although the quality goes down a bit compared to when I don't have the filter on, but its okay for the effects of a CPL.

Now I'm thinking about getting a more expensive "Hoya or such" CPL filter along with some ND filters, My question, should I get the expensive filters, are they worth that difference?

Answer

Absolutely, the best ones are worth every penny. While I cannot say I tried every polarizer out there, I tried over a dozen and kept the 4 best ones.

My favorite by far is the Hoya HD Circular Polarizer which lets one full stop more light than every other polarizer. This is an import advantage since more light lets you shoot at lower ISOs and faster shutter-speeds.

Keep in mind that Hoya makes all grades of filters not just the best ones. Even the lowest quality one is not bad but paying more makes a difference. They have 5 quality levels and the Super Multi-Coated one is very good too but does not match the HD's transmittance.

metadata - Can digital cameras sign images to prove authenticity?

Beyond the metadata/EXIF/IPTC (which can be easily altered), is it possible to prove that an image is authentic? If this is not possible, how does a photojournalist prove the authenticity of an original image?

Can digital cameras sign images to prove authenticity? How does this work, and what cameras can do it?

Answer

Yes, this capability exists to some extent, but not through "signing" the image in the normal sense. It's based on the sensor noise patterns. Jan Lukáš, Jessica Fridrich, and Miroslav Golja (and a few others) at SUNY Binghamton have done work relating to two fields - identification of digital cameras using sensor noise patterns and identification of digital image forgeries using sensor noise patterns.

Something like this paper probably discusses what you are looking for. By detecting interruptions and inconsistencies in the noise pattern produced by the sensors that capture an image, it is possible to detect what parts of a digital image may have been manipulated. It's not a trivial process by any means, but research has been done on using the characteristics of the hardware to perform this type of task.

The last time I did work in this field was about 5 years ago, so I'm a bit out of touch with the latest and greatest, but I do know that law enforcement and the press are both interested in this capability (or at least were 5 years ago). You might have to do some digging to see if/how this has advanced, but it seems to be the best bet at proving authenticity. I just don't see it as something an individual would have on their own.

How to reduce file size without losing quality or resolution?

I have 2,300+ pictures that I want to transfer to my phone but on their original size they take up a lot of space (6.44gb) I would like to trim is down to without sacrificing quality or resolution. I know it can be done under linux with something like pgncrush. I currently have access to a windows system and all the files are on jpeg format.

How do I do it?

Answer

I have found the answer I was looking. The answer is opt-jpg for Linux. I didn't find it on ubuntu repository. So you have to download the source of littleutils (http://sourceforge.net/projects/littleutils/) which has opt-jpg included.

To install from source. Download the Tar with wget and:

tar jxvf littleutils-1.0.27.tar.bz2 && cd littleutils-1.0.24

...

./configure --prefix=/usr && make && make install && make install-extra

You have to be root so sudo su

I used a duck image for example. The un-optimized file is 1.1M after optimization its 991kb without losing any image quality (to naked eye) or changing the resolution of the image. It might not seem like huge difference (a reduction of 108kb) but with 2300+ images and 6.44gb size on average with the same size reduction can add up to a lot of space.

You can see the original Duck image uploaded to flickr:

And the optimized one:

Can naked eye tell the difference?

As for how much space I actually saved. You will have to wait some time because I will have to let it run when I am not using the comp. This will take a while and I will remember to report back.

lighting - What is color temperature and how does it affect my photography?

I have seen color temperature mentioned with regard to white balance, mixing different sources of light, etc., but I haven't come across a clear explanation of what it means to talk about the 'temperature' of light.

How does the color temperature of my light sources effect the images I capture? Are some color temperatures inherently better than others?

Answer

Color-temperature is a way to describe the color of light along a spectrum that goes from warm colors (measured as having a lower temperature) to cool colors (measures as having a higher temperature).

Color-temperature is measured in Kelvin degrees and corresponds to the temperature at which a certain metal must be heated to emit light of that color. That is why lower temperatures (say 3000K) give off warm (yellow-organge) light and that high temperatures (9000K) give off color (blueish) light.

White-balance is the process of canceling the effect color-temperature in a photograph. This is because our brain corrects what our eyes see to let us see white as white, although it may be tinted by the color-temperature of light.

If the color-temperature of light is known, then its effect can be mostly canceled. Automatic white-balance guesses at that temperature (see this question). Preset white-balance use mostly fixed known temperatures (6500K for daylight, 9500k for cloudy, 3000k for tungsten, etc - actual values vary between cameras).

For custom white-balance the camera uses a sample that is known to be white and deduces the color-temperature of light from that. Some cameras actually report the measured color-temperatures when using custom white-balance.

Note that for light sources that are mixed or simply way off from typical lighting conditions (sodium vapor lights, some fluorescents) it is not possible to cancel the effect because some parts of the visible spectrum are missing.

Since colors affect the mood of a photograph and how we perceive images, so does color-temperature. It is known that warmer colors (lower temperatures) are generally perceived as more pleasant and some photographers purposefully set the white-balance wrong to convey a certain mood. Cool colors (higher temperatures) are associated with night and mystery. Neither is better, it must simply fit the photo and how you intend viewers to perceive it.

How can I/should I check the sharpness of my camera lens?

The sharpness of a lens is a major concern for most photographers. This might be because we are worried about a defect in the lens, a problem with our technique or a problem with the camera. Or we might want to select a better lens.

In all these cases it is very helpful if we had an accurate and reproducible procedure for checking the sharpness of a lens that can be used by all or most photographers.

So with that background, how can I/should I check the sharpness of my camera lens?

optics - What kind of mirror in a mirror lens?

A normal mirror, that we see for example in an elevator, is a glass sheet with thin metal coating on the backside, so light reflecting from the metal surface goes first thru the glass.

Metal mirror (aka First surface mirror) has no glass in front and is therefore free of chromatic aberration (practically speaking free, not absolutely). So I'd think a metal mirror would be ideal for use in photographic telephoto mirror lenses. But, in Wikipedia article, it looks like the mirror is made of glass with the reflective surface on the back. Or is this old news, and modern mirror-lenses actually use metal mirrors?

Why is first surface metal mirrors not used in photographic mirror-lenses?

Image by Paul Chin - Wikipedia

Answer

Cost and ease of design.

The main purpose of mirror telephoto lenses is to make them much more cheaply and compact than a conventional refractive lens can be produced. This is easiest to accomplish by coating the back side of a negative meniscus lens (known as a Mangin mirror) instead of creating a parabolic first surface mirror that would need to be shaped and coated in a way that is more expensive to produce and would also require correction for spherical aberration. By coating the back of the meniscus lens the light passing twice through the same lens is corrected by the glass of the mirror itself.

Mangin mirrors were first created for use as catadioptric reflectors in searchlights. They yield better performance and and are less expensive to make than the front coated parabolic reflectors they replaced.

terminology - What does it mean when a TV "supports HDR"?

I am a bit confused about how HDR (on TV) works. The way I see it, multiple images of the same frame are used to create one image which shows better details in low-light and high-light areas of the frame.

Why does the TV have to do anything about this? Shouldn't all movies that have HDR be preprocessed in this way so the resulting movie looks exactly like it should? Or does HDR on TV really mean that these multiple images per frame are available to the TV and the TV figures out how to combine them?

Answer

The answer by James Snell is pretty severely incorrect to say that photo and display HDR are unrelated. They both refer to the exact same thing: higher bit depth. When you create an HDR image, you use the multiple exposures to create a true HDR image that has a higher bit depth than a normal display can reproduce. Because of this limitation, you normally tonemap the actual HDR image back down into the low dynamic range space of a normal display.

What an HDR display allows is to display the HDR image natively without the tonemapping step (assuming the bit depth of the display is greater than or equal to that of the image), whereas on a normal display you're really only able to see a simulated HDR image.

tl;dr HDR = higher bit depth in both contexts. It's not a different meaning at all.

troubleshooting - Why has my 550D camera buffer decreased?

Normally I can shoot 9 JPEG's into the buffer. This amount is indicated by the number in the lower right of the viewfinder, next to the focus confirmation light. Now that number says 2. And indeed, if I shoot more than two JPEG frames subsequently, the camera will hang to write to the SD card and then will proceed shooting further.
This behaviour is independent of SD card speed, JPEG size or quality, or shooting mode.
When I switch to RAW I can shoot 4 frames in a row.

It seems that my camera buffer is partially filled, but I can't find out how to empty it.

Answer

As found on page 220 of the manual, the maximum burst rate can be altered by custom functions for noise reduction set to on. Also, this would explain why in RAW mode you do not experience this, as the noise reduction is probably not applicable to that shooting format.

I would suggest going into your custom functions and disabling High ISO Speed Noise Reduction. You could also do this by resetting the camera if you don't want to find the setting.

metadata - When exactly is "GPSTimeStamp"?

I'm trying to use EXIF data from my photos, and I discovered the wonders of the tag "EXIF GPS GPSTimeStamp" (a timezone-independent timestamp).

However, I notice that it's often different from "EXIF DateTimeOriginal". Usually by a second or two, but I've seen up to 211 seconds difference. The GPS time is usually, but not always, behind (earlier) than DateTimeOriginal. The DateTimeOriginal seems to be the accurate one in the case of a discrepancy. I've checked this for a few hundred photos from 3 different phones.

Does anyone know when, exactly, "GPSTimeStamp" refers to on most phones?

Since GPS signals encode timestamps from literal atomic clocks in space, I assume if the phone receives any signal at all, it will be accurate to less than a second. So that can't be the source of the error.

My current theory is that the "GPSTimeStamp" tells you the time of the GPS fix described in the other GPS tags, not the time the photo was taken. That would explain why it's usually earlier than the DateTimeOriginal. Is that correct?

Answer

Yes, it is the time at which the location was determined. That may be a second before the picture was taken, but it could be much more, if for example you are in a canyon and the GPS is unable to make a fix.

canon - What is EOS iTR AF?

I have read references to this feature on some Canon DSLR cameras and am wondering what benefits or uses it has.

Answer

Canon has introduced a new feature coined EOS iTR AF - Intelligent Tracking and Recognition Auto Focus on the Canon EOS-1D X DSLR.

EOS iTR AF is also now available (as of April, 2019) with the EOS 1D X Mark II, EOS 7D Mark II, EOS 5Ds/5Ds R, and EOS 5D Mark IV.

The camera attempts to detect the locations of faces and focus on these in the scene or alternatively it can identify subjects of a particular color such as in sporting events for example. Face detection is given the highest priority, but if this lock fails it will fall back to looking for the color information.

The default AF mode for the EOS-1D X uses phase detection AF information, but the secondary option uses the face and color detection of the iTR AF. This feature is achieved by using information from the RGB metering sensor as part of the AF system.

technique - How does one focus for landscape photos in very dark conditions?

Tonight I tried my best to take some night landscapes in the darkest of dark conditions. Hoping for an epic composition of the Milky Way and a landmark.

Of course, none of my glass could auto focus with nothing more than dots in the sky to lock on. I seemed to have the most success by lining up the infinity focus mark on the focus window, however, the 50mm 1.8 has no focus window.

How can I set (guess) focus on a lens in relatively complete darkness?

Looking though the viewfinder I see nothing but black. I tried using Live View function to set focus, but that's not helpful either. I'm shooting wide open at f/2.8 or f/1.8 to gather the most amount of light in the shortest exposure, so the DoF is short, and the focus needs to be on.

Answer

In the daylight focus on a very, very far away object, like a radio tower. Mark your focusing ring with a bit of tape or something, and you have your infinity setting.

For closer focusing in the dark carry a laser pointer. Tape it to the camera or tripod so it points at your subject. The red dot should be easily seen through the viewfinder, and it will be easy to tell if you've got it in focus or not. You will probably have to use manual focus. Turn off the laser when taking the photo.

How would IR-assisted white balancing work?

One of the Samsung Galaxy S6's new camera feature is to use its IR-based heart-rate sensor to aid in white balancing. Some of the write-ups on tech websites briefly mention how the IR sensor can 'detect the light around' or 'if a photo is being taken outdoors or indoors' for this feature to work. Are there more scientific explanations to how this works, or will we have to wait for actual reviews to be out?

The general photography angle to this is: are existing cameras DSLRs using a similar method to figure out white balance too?

lighting - Why is the Fluorescent filter for a flash green?

I just bought a Nikon SB-910 speedlight.

The filter that comes with it to use under fluorescent lighting it green, why is this? because certainly to my eye there is not a hint of green under normal fluorescent lighting.

Answer

Balancing for fluorescent lights is harder than say tungsten. The reason for this is that tungsten bulbs produce the same sort of spectrum (set of intensities at different wavelengths) as a daylight balanced flash, just shifted.

A fluorescent light doesn't have the same bell curve shaped spectrum, it produces a set of spikes at very particular frequencies. In particular there aren't many spikes in the red part of the spectrum. The reason you don't see a green tint is probably that the brain is filling in the missing information for you.

Using a green gel on the flash allows you apply a magenta colour tint to your image (to cancel out the green) which helps restore some red that will be missing from the fluorescent lit skintones.

You can never fully replace the missing frequencies with fluorescent lights, and some are much worse than others, for example sodium lights produce very few frequencies, no matter how you try and adjust the colours, there's no information there to recover.

Here's an example of an incandescent light source (a fire!):

Now because this source produces a similar spread of frequencies as the sun, albeit shifted toward orange, we can correct this to a achieve a daylight white balance:

Now let's take a shot under the worst kind of fluorescents:

It looks orange like the first shot. However, even if we shift the image by the same amount we don't get any colours, they simply aren't there in the first place:

So while the filter may help you take out the slight green tint that results from missing certain red frequencies, it wont replace certain colours that are lost.

Fluorescent lights are good for the environment, but terrible for photography. There is hope however, newer designs are improving the width of the spectrum, as defined by their CRI (colour rendering intent) number.

nikon - Why my "action" shots are blurry even shooting on AF-C, is this a lens or camera limitation?

I'm currently using a Nikon 28-200mm AF-D with my D7000. While trying to take action shots (e.g. my dog running or sports) none of the shots seem to be in focus even on AF-C mode. Would this be a limitation of my lens, or the body?

I tried to focus from the minimum focus distance to infinity and it took about ~0.5 seconds, so I'm assuming my lens isn't able to keep up with the subject which in motion.

I was wondering what you guys think the issue is and how I would be able to get sharper action shorts while shooting 6fps.

Answer

There are two issues that are probably affecting your results. Your lens is fairly weak in both areas.

• Auto Focus speed and accuracy


• Camera and/or subject movement

The size of a lens' maximum aperture affects the camera's Auto Focus performance. Not only because the AF system has more light to work with when using a lens with a wider aperture, but also because of the physics involved and the use of edge rays by phase detection AF systems. In general, the same camera with a "faster" lens (one with a wider maximum aperture) can focus more quickly and more accurately than with a "slower" lens. Regardless of what aperture is set in camera, focusing is normally done with the lens wide open. The lens is then stopped down just prior to the shutter opening. Performance of the motor driving the lens' focus elements, including the gearing in the lens, also plays a part.

I'm not familiar with the D7000's available options, but most DSLRs in this class allow you to customize how the Continuous Servo AF works. Through the custom menus you can tell it whether to place priority on focus speed (at the expense of accuracy) or accuracy (at the expense of speed). When shooting continuous bursts you can usually tell it to prioritize one way for the initial shot and then shift to another priority for the subsequent frames in the burst.

The rule of thumb for preventing blur due to camera shake is to use a shutter speed no slower than 1/equivalent focal length. In the case of your APS-C D7000, that means 1/1.5 X the focal length used. At the 28mm end you could use a shutter speed as slow as 1/40 sec if you are practicing good camera stabilization techniques when shooting. On the telephoto end you need a shutter speed of 1/300 sec or faster. Image stabilization would help prevent blur due to camera shake, but your lens doesn't have it. In the case of shooting fast moving subjects like your dog, it makes no difference anyway.

To stop motion of fast moving subjects like a dog or athletes in motion you need faster shutter speeds. Shooting football from the sidelines with a 200mm lens requires about 1/500 sec or faster to freeze the motion. The closer the action is to you, the faster the shutter speed that you need. The only way to get faster shutter speeds in the same amount of light is to either raise the ISO or open the aperture wider. If your aperture is already wide open, then higher ISO is the only way to increase the shutter speed. The problem with higher ISO is that the increased noise (and the effects of using aggressive Noise Reduction) will reduce the amount of detail in the image.

lens - Do old manual focus prime lenses give better image quality than new kit lenses?

Do old MF lenses give better image quality compared to new kit lenses?

I have Sony a6000 and I use it with the kit lens Sony E PZ 16-50mm F3.5-5.6 OSS.

I shoot as a hobby and I am not a photographer. Generality I find the image quality of the kit lens is good, but I read some bad reviews about this kit lens. And the opinion of many people is prime lenses give better image quality (sharpness, colors ...). The kit lens does not make very good background blur so I want a lens with f/1.8

I can't spend money on new prime lens as Sony E 50mm f/1.8 OSS (SEL-50F18) which has very good reviews. Sigma 60mm f/2.8 DN is still too much for me at the moment.

What I try to find now is if an old MF prime lens will give better quality pictures than the kit lens.

How the kit lens Sony E PZ 16-50mm F3.5-5.6 OSS compares to the old prime Minolta MD Rokkor 1.7 50mm (or other similar lens within the same price range)?

nikon - Is it necessary to turn off lens-based VR before turning off the camera?

I just bought a D3100 and started reading its manual. On the lens' Vibration Reduction chapter it said that the VR should be turned off before turning off the camera, every time I use it. Is it really necessary? Why?

I think the manual said it had to do with the lens stability, after the camera is turned off...

Answer

It depends on the lens, but it's a god habit to get into. Doing a "safe shut-down" ritual on a lens that doesn't need it has far fewer consequences than skipping the step on a lens that does.

In-lens optical stabilisation systems work by floating one or more lens elements under the control of servo motors. While VR (or IS, or whatever the brand name is on your camera) is active, there is no firm mechanical connection between the lens's stabilisation element(s) and the body of the lens -- it's essentially free to flop around inside the body if the motors aren't running. If you shut off stabilisation on the lens while the camera is still powered up, the element is returned to a neutral position and mechanically locked in place. If you don't, then the lens is still free, but there's no longer a motor to keep it in place.

Not only does that mean that the lens is less delicate to transport, it also means that if things go wrong and the element gets stuck, you're left with a non-stabilised lens that has all of its elements centred. If the element were to become frozen somewhere outside of its normal range of controlled motion, you'll be left with a lens that is visibly degraded; softness and vignetting will be centred around the lens's optical center, which will no longer be the centre of the image. In other words, you'll have a lens that makes really nice pictures only if you keep the subject, say, left of centre in the image.

I remember a time when we had to run a head-parking routine on hard disk drives before shutting down a computer. It wasn't always necessary, but if the computer were bumped or moved with power off and the heads unparked, there was a good chance that you'd lose your disk. Modern drives (basically everything made since 1993 or so) autopark the heads -- the "park routine" is just a spring, so you don't have to use the motor to move the heads to a safe position. VR/IS lenses will probably be the same as time goes by -- but it's the lens you're using, not the camera, that determines whether you need to let the stabilisation system centre under power or not.

focal length - Lens for 1/2" sensors, installed on a 1/3" sensor

I want to install a lens built for sensors 1/x" (with 1 <= x <= 3), on a sensor 1/3". I need to have an horizontal field of view of "a cm", when my working distance is "b cm". What is the formula of the focal length (where the lens is initially adapted for sensors 1/x") I need , please ?

autofocus - Where is the AF sensor located in a DSLR?

As I understand every DSLR has a separate, smaller sensor that handles phase detection focusing. Where is it located?

If this location is different for every DSLR, and therefore this broad question can not be be answered, where is the AF sensor on a Canon 550D located?

Answer

It's generally at the bottom of the camera body. The reflex mirror permits some light to pass through it, which bounces off a secondary mirror which hangs underneath the main mirror, through a lens, off another mirror though another lens and into the AF sensor:

The reason for all of this bouncing around off mirrors is that the AF sensor has to be exactly the same distance from the lens as the main imaging sensor in order for the phase detect AF to give accurate results.

Here is a cutaway drawing from Canon of the 50D, showing the different mirrors and the AF sensor itself. It appears all Canon DSLRs use the same arrangement for the AF lightpath:

exposure - When I change the EV compensation, how will that affect my aperture, shutter speed, or ISO?

Let say that we have the following values, as an example:

Shutter speed: 1/40
Aperture: 2
ISO: 1000

How can I get the EV number for this exposure, extract (or add) an EV value (0.33, 0.66 etc.) and calculate back the new shutter speed (or ISO) value?

In fact I want to calculate how the Exposure Compensation will affect my values.

Answer

The Exposure value can be calculated with the given Aperture and shutter speed using the following formula:
(src: wikipedia)
where,
N: Aperture value
t: Shutter Speed

The above EV is for ISO 100 called as EV100. EV For subsequent ISO values is calulated with help of EV100 using the following formula:


where,
EV100: EV from the first formula
S : required ISO value

The Exposure compensation works by adding or subtracting the required Exposure compensation value with the current EV to get the new EV.
This new EV can be reverse engineered with the above formulas to get the Aperture and Shutter speeds.

Applying the values you have given:

EV100 = 7.32  //At ISO 100
EV1000 = 7.32 + 3.32 = 10.64  //At ISO 1000

On applying Exposure Compensation of 0.33:

EV(new) = 10.62 +0.33 = 10.95

Now reverse engineer this value to get N and t accordingly.

Why would you want to take pictures without a memory card in your camera?

Canon DSLRs have an option to shoot pictures when there is no card installed in the camera. This option is enabled by default, and it got me too many times before I realized it can be disabled in the menu.

I was wondering what is the use of such mode. The only one I could think of is when you shoot tethered. Are there any other cases where it would make sense to shoot without a card?

Answer

The main reason for this option is commercial - it allows the camera to be tried out in a shop and see the result of their test. Without this, you wouldn't be able to properly try out cameras. Normally, cameras allow just a small number of test shots to be stored.

How do I prevent condensation in my waterproof GoPro casing?

I've recently been getting into whitewater rafting and have been using my GoPro on my trips. However, over time condensation will slowly build up inside the waterproof casing and obscure the lens (usually because I end up in the water).

Since I'm in an environment where water is present, I'd rather not use the open back casing nor do I want to open up the casing to equalize the temperature between the interior and exterior of the casing. What can I do to prevent fogging within the GoPro case when I take it out on the water?

Answer

What can I do to prevent fogging within the GoPro case when I take it out on the water?

An important assumption that you must confirm is that the condensation is due to moisture present inside the camera at sealing time and is NOT caused by water ingress during operation. If the camera is sucking in water, then you have a problem that must be repaired.

If the condensation is due to moisture in the air in the camera it usually occurs because the outer case is cooled to below the dew point of the internal air. You overcome this by lowering the dew point of the internal air, which you do by drying it.

You can dry air with a dessicant OR by cooling it to below its dew point so that water precipitates out. So ...

Some mix of:

1 - Use a desiccant inside the camera. silica gel is one. There are others available commercially. Wikipedia is useful They note -

• . Some commonly used desiccants are: silica gel, activated charcoal, calcium sulfate, calcium chloride, montmorillonite clay, and molecular sieves. I have been very impressed with both Montmorillonite_clay and Calcium Chloride.. Both of these can make a mess by liberating liquid water after capture if arranged poorly BUT a properly designed system can capture and retain far more water than you should have inside your housing.

2 - Close case when air is as cold as possible (low RH for a given situation). If you seal the case at home or in an environment when power is available you could use a modest peltier cooler to achieve lower temperatures than you will otherwise be likely to get.

3 - Use dry air when sealing. eg pump air through a dessicant with a squeeze bulb or similar and flush inside of camera with this air before sealing. Doing this when the air is cool is a bonus.

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Choice 1 can be used in conjunction with others.

Choice 3 is arguably the most "real" one as it provides air that is as dry as you can reasonably make it. Even better if it is cool when sealed as the RH will drop as the temperature rises.

What to look for when testing a wide angle lens before buying?

I'm looking at buying a used wide angle lens (specifically Canon EF-S 10-22mm f/3.5-4.5 ) for a crop camera. The question What should one look for when buying a used lens? covers the basics when buying a used lens.

I'd like to get tips about what to specifically look for when testing a wide angle lens. What are most likely to be flawed with a wide angle lens and how to test for these flaws. How to push the limits of the lens to make sure it's not one of the few with serious problems.

Keep in mind that the testing will happen in an uncontrolled environment, like a shop, public place or at the sellers house. This means that the test have to be quick and easy without using a rigid test setup.

Answer

It will be difficult under such circumstances to do anything but a cursory inspection. The best advice would be to know the lens you are going to buy and it's particular quirks.

Ideally, the seller could send you a picture taken with the actual lens in advance, so you could see for yourself, barring that, if you could bring a camera and a laptop, and try some tethered shooting, you could get a good idea of any issues pretty fast. If that's not practical, at least bring a lens and do some chimping.

Check for general condition and functionality. Specifically for wide angle, the obvious things to check for are corner sharpness, fringing, vignetting, and amount of distortion.

Obviously, any wide angle lens is going to go have all of those to some degree, which is why you have to know what to expect going in.

equipment recommendation - What film rangefinder camera can I buy for a reasonable price?

I'm interested in trying out film photography and I would also love to try out a rangefinder camera as those seem to be perfect for manual focusing in street photography.

Now, of course, the question is: Which camera and lenses should I buy? What are the differences? I'm all new to these cameras, so don't hesitate to include some very basic stuff in your answers :)

Regarding the price: As it is an experiment, I don't want to spend any more than 1000 USD in total for the beginning. If the whole thing turns out to be not for me, I should be able to sell the equipment for a good price, right?

Answer

If you're willing to reduce your budget by a factor of 10, you could get a Canonet QL17 GIII, which has a permanently mounted 40mm f/1.7 lens and shutter-priority auto exposure. I really enjoyed mine and considered it an excellent value. The 40mm focal length suited me well, and the lens "drew" nicely, with sharp focus and pleasant bokeh.

flash - Are flashes really subject to a "use it or lose it" problem?

I was just reading the manual that came with my new flash and stumbled over this warning:

14.3 Flash capacitor forming
The flash capacitor built into the flash unit undergoes physical change if the unit is not switched on for a prolonged period. For this reason it is necessary to switch the unit on for approximately 10 minutes at least once every three months.

Is this seriously a problem? How long does a flash have to sit idle before it has issues?

What kind of issues would I see? Slower recycle times? Inability to recycle? Total failure to power on?

Answer

With electrolytic capacitors, disuse can cause slower discharge, and longer recycle times, which can be restored by firing and recycling the flash a few times.

If you don't use them for a long period, the non-conducting dialectric can break down to the point they will short circuit.

Periodically turning it on will charge the conductive plates and this will prevent the dialectric from breaking down.

Image stabilization in aerial photography

Is image stabilization useful when shooting from a flying plane or helicopter?

Answer

Yes, it can help minimize camera shake. To take it to the extreme, serious aerial photographers sometimes use a gyroscope mount.

Related but not directly answering the question: you want to ensure that the camera is not touching the airplane or helicopter - you'll end up transferring all sorts of vibration from the aircraft to the camera.

nikon - Is there any way to recover photos taken without a memory card?

I went out today and took over 75 photos with my Nikon Coolpix P100, but I didn't have a memory card in my camera. I'm now unable to retrieve any of the photos - is there any way to recover them?

focus - What are the biggest issues with wearing glasses as a photographer and how can they be overcome?

To be clear, I'm talking about the photographer wearing glasses.

I wear glasses and I find that I continuously need to make sure my glasses are pushed up on my nose and that having things at the wrong angle can distort things. Some things I am wondering about that I would like incorporated into your answers:

• Do you have trouble looking through the viewfinder?


• Do you prefer contacts over glasses?


• Do you find it harder to manually focus?


• Do you have a special viewfinder? (I think I have seen things online that are the equivalent of a prescription viewfinder?)

Answer

I wear glasses, and I'm a good photographer (so I'm told).

Do you have trouble looking through the viewfinder?

No. You get use to it after a while.

Do you prefer contacts over glasses?

I have no preference when taking pictures, however my preference in general is using my contacts.

Do you find it harder to manually focus?

Not because of my vision, but because the default screen does not lend itself well for manual focus. A split focus screen will helps quite a bit.

Do you have a special viewfinder? (I think I have seen things online that are the equivalent of a prescription viewfinder?)

No. Every DSLR body I've used comes with the ability to change the diopter of the viewfinder which may allow you to use your camera without your glasses.

What are the biggest issues with wearing glasses as a photographer and how do you overcome them?

For me, the biggest issue was getting over trying to force the camera's body against my face while wearing glasses. This is extremely uncomfortable. Now I don't use as much pressure, and it's much easier to shoot.

nikon - Can I control the aperture of a F-mount lens with aperture ring from the camera body?

If I buy a lens with a manual aperture ring like the Nikon AF 50mm f/1.8D, then does that mean that I can only control the aperture on the lens? Or can the camera control it too? I want one with manual aperture, but I also want the camera to be able to control it when using presets.

My camera is the Nikon D3300.

Answer

When using Nikon "D" lenses on a newer Nikon body that controls aperture from the body you lock the aperture ring on the lens at the narrowest aperture. In the case of the 50mm f/1.8D that would be at f/22.

Be aware that Nikon "D" lenses are normally AF lenses that do not have an autofocus motor in the lens. Nikon AF lenses require a body with an in-camera AF motor to allow use of AF. When used on Nikon bodies with no in-camera AF motor AF lenses must be manually focused. AF-S lenses have focus motors inside the lens and are required to use AF with your D3300.

I want one with manual aperture, but I also want the camera to be able to control it when using presets.

There are only a very few Nikon "D" lenses that are AF-S that would give you both an aperture ring and the ability to autofocus with your D3300. But with "D" lenses you must lock the aperture ring in the narrowest position and use the camera to control the aperture with newer entry level Nikon bodies such as your D3300. Otherwise you will get an "fee" error and the camera won't take a picture. The aperture ring on "D" lenses may only be used to control the aperture with older Nikon bodies that don't allow you to set the aperture from the camera or with newer upper tier Nikon bodies that have a custom menu function that allows you to choose whether to control the aperture from the camera or using the lens ring.