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 has a narrow angle of view, so it would make sense that the angle would be smaller. However, this is the opposite of what one can see on real lenses.

Why is this the case?

Answer

That is a generalization that is not always true.

The front element is not only sized to accommodate the field-of-view but also for the maximum aperture. Since aperture is measured as a fraction of focal-length, a longer lens requires a physically larger aperture to reach the same F-stop.

For example:

• The Nikkor 200mm F/2 lens requires an aperture 100mm across and you can see from the spec that the lens diameter is 124mm.


• The Nikkor 35mm F/2 lens requires an aperture 17.5mm across and you see that the diameter of lens is much smaller.



• The Nikkor 300mm F/4 lens requires an aperture 75mm across, so although it is longer than the 200mm F/2, does not need to have such a large front element and its diameter is 90mm.


• The Nikkor 14-24mm F/2.8 is an ultra-wide lens with a diameter of 98mm although its aperture only needs to be 8.6mm across (24/2.8) but it ends up much wider to accommodate the field-of-view.

Contradiction in information resources on capturing UV light with a digital sensor

I encounter a contradiction.

Many resources state that a digital sensor are unsensitive to UV light. Even wikipedia, "However, newer photographic film and digital cameras are highly insensitive to UV wavelengths." http://en.wikipedia.org/wiki/UV_filter. Digital Photography Review goes even to the point that a digital photographer won't even need it on a beach (an UV-light rich area). "digital sensors are not and hence do not need UV filters in even bright sunlight". http://www.dpreview.com/articles/8049091537/the-uv-filter

While other resources state that digital sensor are sensitive to UV light. Are digital sensors sensitive to UV?

Can someone clarify this contradiction?

My prognosis is that a digital sensor is sensitive to UV light, but sensor manufactures include an UV blocking system on the sensor. But I don't know if that's true. I do know that IR light is blocked through a IR-absorption glass on the sensor itself.

Is my prognosis correct?

Answer

Most digital sensors are sensitive to UV to some degree, and most have UV/IR cut filters installed over them to keep that sensitivity from throwing off visible light colors. However, removing the cut filter to let in the full spectrum, or using a pass filter and long exposures, doesn't really solve the issue of allowing the camera to shoot in UV, because the majority of lenses also have UV cut coatings on them. Few lenses are suitable for UV shooting, and the ones that are tend to be expensive and rare (e.g., the UV-Nikkor 105 f/4.5), which is why this is a much rarer and more esoteric form of photography than IR shooting. It's most commonly done by forensic photographers.

See: All You Ever Wanted to Know About Digital UV and IR Photography, But Could Not Afford to Ask

equipment damage - Is it ok to breathe on the front glass element of a lens to fog it and clean it?

Nikon specifically recommends not breathing on the glass elements to clean them as harmful acids in the breath can damage the coatings on the glass.

However, I've read on many other websites that it is OK to clean the lenses in this manner.

What are the potential pros and cons of doing it?

NOTE: Shortly after this question was posed Nikon removed all references to the issue of breathing on Nikon lenses from the page at the above link.

Answer

Ever since I posted this question here, this has been featured on 2-3 websites:

Although I'm not sure if this was a direct result of posting this question here.

Nikon has now updated the support page and removed the statement where it said that breathing on the glass could damage the lens coatings due to presence of harmful acids in the breath.

Canon 700d - lens does not move when focusing?

I have a canon 700d. I have seen other 700d's, and when they focus the lens automatically moves in and out. My one doesn't. Why would that be?

troubleshooting - Why is the sky in photos always too white?

Why do I never seem to get a clear picture of the sky during the day, even with white puffy clouds in the sky? It always looks over exposed and whitened out? I am using a Nikon D3100, no lens hood, manual setting.

exposure - What's a good ad-hoc replacement for a gray card?

I know that a real gray card is the best thing to use to determine exposure. But I'd like to know if there are other naturally available features that can be used in a quick and dirty way. Are fields of grass or road tarmac appropriate?

The reason for asking is that I suspect that my new used (manual focus) lens is exposing incorrectly using my camera body. I don't have access to a gray card, but I do have access to lawns and pavements, nicely and evenly lit by a cloudy sky.

Answer

Grass is generally considered to be 18% grey. I would guess if you shoot in grey scale mode and your exposure is said to be correct, it should come up 18% grey.

There's also the sunny 16 rule, which is on a sunny day, shoot at 1/ISO shutter speed, f16. This should produce a correctly exposed picture. You can check to see if this results in a correct picture.

Both of these were tricks I was taught back in film days.

aperture - What's the base f-stop when counting an ideal f-stop for lens?

I've read a lot around this site that an ideal quality of the lens is achieved when using f-stop roughly 2 stops slower than the fastest value of the lens.

Firstly, I'm not exactly sure what "2 stops" mean when it comes to f-stop, but this isn't really important in what I'm about to ask. What I'd like to know is what is the base f-stop when counting this value.

Let's look at it this way: If I have a prime lens with f/1.8, then obviously I'll be getting the ideal value from f/1.8, let's say after 2 stops I get f/2.8?

But! What in case of zoom lenses, for example 18-55, which have f-stop f/3.5 - f/5.6. Should I take f/5.6 as my base value, or does the base value depends on the real fastest value at the exact focal length?

Therefore, if I set the lens to 18 mm, their fastest aperture is f/3.5 and thus the ideal quality is at f/5.6 and when I set it to 55 mm, their fastest aperture is f/5.6 and thus the ideal quality is at f/8 ? Or is it f/8 for the whole focal range ?

Answer

Real fastest value at the exact focal length.

But, this is just a rule of thumb — it's not necessarily exactly two stops in every case.

For the question of what two stops mean, see What does f-stop mean?. In short, each stop is approximately the-square-root-of-two times the previous one. That means half the light is allowed in (which is why the seemingly-weird series of numbers was chosen). Two stops is doing that twice, which conveniently works out to simply being doubling. Two stops from f/2 is f/4, and and two stops from that is f/8. Or, starting at f/1.8, two stops is f/3.6.

The test results comparison tool used by Digital Photography Review is interesting for looking at this. Try this test of Pentax's 18-55mm zoom, which like most kit zooms goes from f/3.5 at the short end to f/5.6 zoomed out.

You can see that at 18mm, the sharpness improves as you go from f/3.5 to f/4 to f/5.6. At f/8, it's more even from center to corners, but doesn't get any sharper. And beyond that, it drops off.

Then, change the focal length to 55mm. You'll notice that with this lens, overall sharpness goes down from 18mm at f/5.6. At f/8, it picks up a little bit, and a little more at f/11, and then back down again at f/16.

So, that fits with the two-stops guideline pretty well. Same for the Canon kit lens, and Nikon too.

With the Pentax DA 15mm f/4 Limited test, they've got test results in third-stops, and there you can see that f/7.1 is no better than f/6.3, and f/8 is worse — so that's only 1⅓ stops. On the other hand the DA★ 55mm f/1.4 shows peak sharpness at f/4.5 — closed down by 3⅓ stops. This doesn't reflect a problem with the lens, just different priorities in design. The Nikon 50mm f/1.4G is similar, with peak sharpness at 3⅔ or 4 stops down. However, the entry level Nikkor f/1.8G fits the "two stops" guide quite well, peaking at around f/3.5.

It's also worth noting that this test is primarily concerned with sharpness, because that's easy to measure. Other image quality and rendering characteristics are also affected. Vignetting (light falloff in the corners) gets better the more you stop down, and it's usually gone after two stops. And bokeh quality is usually improved by stopping down, too — generally, lens bokeh is nicer/smoother stopped down a bit, but of course it's less visible since you have greater depth of field. Plus, shape of the aperture blades will become visible in specular highlights, which is a side-effect unrelated to stopping down per se — some modern lenses have rounded aperture blades to make that not be a concern.

Is there always a way to capture all the light ranges to get good HDR images?

Let me explain the question. I've been making a lot of HDR photos, most of them in places where the difference between darker and lighter zones is no to big, and the transition from one zone to other is slight. And I get quite fine HDR photos.

But when I take photos in night, where you have a very big range between lighter zones (lamps) and darker zones; and the transition is strong, I can't get good HDR photos.

I mean, the dark zones close to the light ones, get an ugly glow that can't be removed. Even in the source images that will later compose the HDR image.

Is that just "light nature" or something else?

What do you do in this cases?

EDIT

In these cases, I tried 7 stops with +/- 1 EV., but I still can't have good HDR photos.

Answer

When it comes to HDR, it is important to understand the true nature of what your are doing. High Dynamic Range images contain a floating-point dynamic range that is nearly infinite. No device that exists is actually truly able to render the full dynamic range offered by a 32bit HDR image. To be able to view your HDR images, you ultimately have to downconvert them to a smaller integer bit depth, such as 16bit or 8bit. When you do so, you are mapping tones from the full range provided by the 32bit floating point image to the limited range of 16bit or 8bit integer images.

Even though a 32bit HDR image can technically contain and represent an immensely wide dynamic range, its beyond visibility on any modern computer screen, and well beyond what any printer is capable of. In cases of extreme contrast, such as photographs with the sun in them that also include deep shadows, or in your case, night photographs that include artificial lighting via lamps and the like, there is simply too much contrast to compress into a 16bit or 8bit integer image or print. If you try to tone map such an image, you'll undoubtedly get things like posterization, harsh edges around highlights, undesirable color shifts, excessive noise in shadows, etc.

There may be some things you can do to improve your images when taking the shot. Providing extra lighting for the shadows is the first thing to try. Flash can be useful for filling in some light into deep shadows. You may need to bring along some extra lighting. Try following the ETTR technique, or Expose to the Right, where you overexpose your shots as much as possible without clipping highlights (or in your case, you may want to clip them a little bit because of the extreme contrast difference). This essentially dedicates more of the sensors dynamic range to capturing shadow detail. You can recover highlights in post-processing, and effectively achieve a more balanced shot. Try combining ETTR with some fill-flash as well to get the best shots possible.

You might also try Exposure Fusion, which is an alternative process to HDR. Expose a few shots, one to capture the bright highlights of street lamps and the like, and a few overexposed shots to capture as much shadow detail as you can. Using a tool like Photomatix, you can "fuse" the exposures together to merge shadow detail into shots that contain highlight detail. The result is similar to HDR, but simpler and often produces more natural results.

Finally, some of the exposure stacking tools for night sky photography might be helpful with images that have had their shadows lightened but display too much noise. Using burst mode of your camera, snap a rapid sequence of shots of the same scene (best done with a tripod/cable release to avoid changes between frames) that covers as much contrast as you possibly can in a single shot (ETTR might help here as well). Recover shadows and fill light with a tool like Lightroom, and merge a sequence of a single scene together in a photo stacking tool designed for stacking astrophotography shots. These tools excel at merging images and eliminating noise in the darker parts.

Note that for almost all of these things, it is important to work in RAW through the whole process if you can. Don't convert to TIFF or DNG, use copies of the original RAW files from your camera. This is particularly important if you take the astrophotography stacking route, as those tools have a variety of pretty advanced algorithms that work directly with bayer array data to produce the most ideal, low-noise results when stacking.

lens - What lenses to bring while traveling? One good wide-telephoto or several smaller ones?

I have a Canon 7D and often take my camera on the road while traveling. In the past I've taken my Sigma 17-70 f/2.8-4 and my Canon 70-300 f/4-5.6, which means that I must switch out lenses quite a bit, depending on what I'm shooting. I get a much better overall image with the 70-300, but the 17-70 gets the big picture. Should I invest in a third lens for better travel portraits, close-up lenses to save space, or just a better lens overall (such as the Canon 24-105 f/4L)? I do love having low f stops for great focus and blur, but I also like having options, macro equipment, and reach. Perhaps there's no easy solution, but what would you do to travel relatively lightly in such a situation? Thanks!

What is a "2.2X Pro Telephoto" lens?

I am looking to enter the world of SLR cameras and learning some more about lenses. I came across a package that has a 2.2X pro Telephoto what exactly does that mean and how does it work? (Please explain it in lay terms I am new to the lingo here)

Answer

I'm assuming you mean this: Raynox DCR-2025, Pro 2.2x Telephoto Lens for Digital Still Cameras. In this case, beware of the word "pro", as it doesn't mean anything — Raynox just sticks that on all of their similar products to make them sound fancier. It's also disingenuous and confusing for Raynox to call this a "telephoto lens", because it isn't really.

This isn't a stand-alone lens, but is rather a "teleside converter" made to increase effective focal length of a "real" lens. It's made to give additional options for digicams and camcorders without interchangeable lenses, and it works by using lenses to increase the width of the incoming beam of light. You could conceivably use this on an SLR lens, but I don't think you want to.

In general, they're not really a good deal, since even when you can't change lenses, you can often get better image quality just by cropping. That's because the additional optics destroy detail, so you loose image quality. Might as well lose image quality for free by cropping the image to just the detail you're interested in.

If you really want to use a teleconverter, the kind which goes between your primary lens and the camera usually offers better image quality, although that kind also restricts the effective aperture. But I think probably what you actually want is a real telephoto lens.

lighting - How should I build a portable light box for shooting beer bottles?

I am working on a beer related website, and I would like to build a portable light box that I can take to a beer shop and photograph as many individual beer bottles as possible. What is the best way to construct this to ensure proper lighting and the ability to rapidly swap out beers and snap photos?

Answer

There are plenty of light tents on the market that would suit your needs:

Light Tent - Google Shopping

If you want to go the DIY route, your best bet is to choose a decent piece of diffusion material (thin plastic / acrylic are good for this) and make a tall three sided pyramid and fire the flash through the diffusion material for even lighting, see:

Strobist - A Ping from Ming on the Bling Lighting Thing

This setup really favours shooting from above however you could build a two sided box with sides at right angles which would give you the ability to quickly swap out bottles. When shooting glass you want the lit-up diffusion material to make up as much of the space around the bottle as possible so you don't get odd reflections of your light tent in the glass.

Is there a rating, spec or measurement that a buyer can use to compare how fast cameras can autofocus?

I know that Phase Detection autofocus is faster than Contrast Measurement autofocus.

Is there a spec that can tell me whether one DSLR or compact camera can achieve autofocus on a subject faster than another camera?

This information should be useful in picking cameras for photographing sports, birds, insects, race cars, et cetera.

Answer

Sadly no. Even worse, it is vastly unpredictable due to consistency at different focal-lengths, aperture and focus-distances. For DSLRs and SLDs, the choice of lens greatly matters too.

A number of review sites have methodologies and quote numbers in ms or fractions of a second which gives one relative measure but it not easy to generalize. In other words, you may get measurements saying that camera A is faster than B, but in another situation it is the contrary.

For compact cameras, the few that use Phase-Detection like the Fuji F300 EXR have the lead, followed by bright apertures ones like the Olympus XZ-1.

Among DSLRs, generally the ones with faster continuous drive usually have a fast AF and price to match.

Finally for SLDs, Sonly Alpha SLT use Phase-Detection. The Nikon 1 V1 and J1 also use Phase-Detection and claim to be extremely fast, although I have not tried them yet - one should be arriving soon.

lens - What are the differences among these Canon telephoto zoom lenses?

I am using Canon 500D with the kit lens (18-55). I think I have done enough with 18-55 and want to try out next lens. I have already decided to purchase 50mm prime. I also wanted to get a Zoom lens. When I looked around Amazon, I see many varieties of zoom lenses.

I have 4 questions.

First lens in the above list is $524 and rest everything under $200. I am wondering why such a huge difference? Is it because first one has USM in it?

I am obviously confused and request for expert help to choose which one to buy. Is there a problem in buying lens without USM? Will the low pricy one reduces image quality?

My friend uses Nikon and is there any zoom lenses available which can be mounted both on Canon and Nikon?

I have also seen people recommending Tamron AF 17-50mm F/2.8 as a choice for Zoom lenses. Is this the better choice? If yes, how it is better from longer ranges like 70-300? Since this lens offers F/2.8, can this be also used for portraits?

I shoot whatever I like, but mostly landscapes. Any help would be appreciated!

What are the uses of yellow, green, red, blue filters in black and white photography?

Could someone explain the difference in using colored filters for black and white photos? What is the best practice using these filters for portraits, landscapes, macro? For different types of weather: sunny, foggy, morning, evening, and so on?

Answer

If you are using a digital camera, there is little need to use colored filters, as you can apply their effects in post processing when you do the black and white conversion.

See Are there reasons to use colour filters with digital cameras?

Also How can using a color filter help to improve a black and white photo?

If you are shooting film, then

• Red is commonly used in landscapes. It will darken foilage, and will dramatically increase the constrast in cloudy skies. It will lighten skin if used in portraiture.


• Orange behaves like red, but effects are less.


• Yellow has a subtle effect - will darken skin slightly.


• Green will lighten foilage. It can be used in portraits to darken the skin


• Blue will lighten skies, and lower contrast if you want a hazy effect

35mm - Got back my film - Nikon FM2 missing shots, blue marks, what happened?

I'm shooting a Nikon FM2 (35mm) with Kodak Vision3 500T (24 exp) repurposed film from The Film Photography Project.

I got scans back (26 images). There's some blue lines - I imagine that those are due to the friction I heard when trying to advance the film in my camera.

Something else - I'm missing a large portion of the end of my shoot. I don't remember looking at the film counter when shooting - I just kept advancing the film until it wouldn't let me anymore, thinking the slight friction that I was feeling/hearing was due to the stiffer movie stock film. It's possible I went past 24 and continued until the camera wouldn't let me advance anymore. There are no multiple exposures on any of the images I received back, though I guess it's possible, if unlikely, that they exist and the lab just didn't send them to me.

What happened to the rest of the 'shots'? I am guessing that some sort of camera error occurred to where I was no longer shooting anything at a certain point, since the shots I'm missing are all in a big chunk at the end.

I had two rolls - and I remember switching rolls at some point, but I'm fairly certain I only took 3 shots on the most recent roll. The camera counter said that, at least. I guess it's possible that the counter was broken and all of the missing 'shots' are on that second roll. I don't think that this is the case - certain details that I remember about the shoot suggest this isn't what happened. I haven't gotten the second roll of film developed, but might based on the advice I hear here.

I'm lost as to what may have happened here. This was for a shoot over a month ago so my memory is a bit hazy, but I know I'm missing a large portion of the shoot (I estimate 8-12 photos) - and that it was towards the end. Any help would be appreciated!

edit: this is bulk loaded film. I've read that it's difficult to tell when it 'stops'. Is this the issue and how would I prevent this in the future?

How does a lens affect the saturation of a picture?

In many reviews people describe how a lens can affect the saturation of a picture, especially when it comes down to a comparison of two similar lenses, e.g. 50mm 1.8 vs. 50mm 1.4 or something like that and they point out that one lens is delivering stronger colors than the other one.

What is responsible in a lens to affect the strength of a color?

Answer

The quality and makeup of the lens elements used in a camera lens can have an effect on transmission. Top-notch glass will usually have high transmission, allowing through as much visible light as possible while filtering as little as possible. However, top-notch glass will also usually have coatings, usually multi-coating, that will have its own effect on transmission, and may introduce color cast or affect flaring. Glass that is not coated or cheaply coated will usually exhibit more flaring, which can have a significant impact on scene contrast.

Cheap glass may not have a high transmission index, in which case for a given exposure value, the overall contrast may be lower than quality glass that has a higher transmission index. Contrast affects both luminance as well as color saturation, and lower overall scene contrast in a color photo will usually also affect the apparent saturation of color. Cheaper glass or cheaper lenses may also exhibit various optical aberrations, many of which are explicitly related to the convergence or divergence in how different wavelengths of light focus. This can create purple/green fringing as a scenes depth progresses and focus changes, which can also have an effect on color and saturation.

Higher quality lenses will usually have better control of flare, higher transmission glass, better multi-coating that has a minimal impact on transmitted light, fewer optical aberrations, etc. etc. This all affects the ultimate quality of the images produced, and is most visible in contrast (both overall scene and micro contrast, the latter being an effect of lens resolution) and color saturation. Thus is the benefit of a high quality, more expensive lens...you really do get what you pay for.

exposure - How does this TLR camera expose properly?

I found a DIY TLR camera kit that lets you build the camera from parts, then use it to take photos. What I don't understand, is that the specs list:

1/150s shutter speed; f/11 aperture

From that description, it makes it sound like it has a fixed shutter speed and aperture. Assuming I use 24 or 36 exposure 35mm film, am I limited to one set of exposure values for the entire 24 or 36 frames? I am thinking I might be misunderstanding how TLR cameras work.

Answer

This is very similar to a Holga medium-format toy camera, where the shutter speed is approximately ¹/₁₀₀th of a second (give or take the particular camera you have and how it is feeling today) and the aperture is about f/13 (regardless of whether you have the alleged aperture lever set to one of its two non-functional options).

So how do you get the exposure right? You shoot in lighting that's right for the film speed you've chosen. You depend on the greater exposure latitude of film when it's off by a bit, and don't worry so much about getting it perfect. Or close to perfect. If you wanted it perfect, you wouldn't have a plastic DIY camera, right? Rather than control and execution of vision, it's about happenstance and creation through serendipity.

PS: this isn't normal for TLR cameras in general. It's normal for toy cameras, though.

What's the benefit of a tiny aperture?

In this answer to another question Rob Clement wrote:

Think background first. What story do you want to tell? Epic background, big mountains. Looking to deliver a sense of grandeur with your subject. Go big! f/22 or higher if you have it.

I understand that he's using depth of field to talk about keeping the background sharp. But even at a modest f/8, the hyperfocal distance for most common scenarios is only a few tens of feet... more than enough to get a mountain range in.

I also understand that wider apertures reduce sharpness... but a few stops down from wide open is usually enough.

And obviously, you can use a smaller aperture to reduce the light. But f/22 seems pretty tiny even for a bright day.

So what other reasons for using a tiny aperture exist?

Answer

Those kind of apertures often show up in macro work because the DoF is razor thin, so every fraction of a mm you can get matters. However, you also can be diffraction limited at such a aperture and actually end up with less sharpness. Cambridge in Colour has a good article on this very topic.

mirrorless - How can a speedbooster improve the light performance of a lens?

I have been reading couple of times now about those new speedboosters for mirrorless cameras. They are being reviewed as improving the low-light performance of a lens by one full stop.

In my knowledge, when you add elements to a lens, you would make the image not better, but rather worse. Can someone explain me how this works in general terms?

Answer

If you shine a torch (flashlight) on a wall and walk forward, the circle of light gets smaller, but brighter at the same time. The principal of the speed booster is the same.

A lens designed for 35mm projects an circle of light at least 43mm in diameter onto the sensor. The sensor in an APS-C format camera has a 28mm diagonal. The "speed booster" concentrates this 43mm circle down to a 31mm circle. Because the same amount of light is now falling on a smaller area, the amount of light per unit area is now increased.

Looking at it from a different point of view, the speed booster reduces the focal length of the system whilst the physical size of the aperture opening remains constant. Thus the f-number, which is the focal length divided by the aperture diameter, decreases.

Focal length changes by a factor of 0.71, thus the f-number changes by a factor of 0.71 which just so happens to correspond to one stop.

Fundamentally it's the exact opposite of what happens with a 1.4x teleconverter. A teleconverter increases focal length whist keeping the aperture diameter constant. Or alternatively a teleconverter enlarges the image circle but reduces intensity at the same time.

---

There are some other bold claims made by the manufacturers of the speed booster. In addition to increasing speed by a stop they also claim the resultant image is sharper, which goes against conventional wisdom.

However, the statement "when you add elements to a lens, you make the image worse" is not true absolutely (obviously if you remove elements from a lens you can make the image substantially worse, thus it is possible in theory to improve the image quality by adding elements).

It's true that each extra glass element will increase internal reflections and potentially introduce aberrations. Most add on filters are designed to make the lens do something it wasn't designed to do, e.g. focus at macro distances. However it's possible to use additional elements to correct aberrations present in the original design.

The speed booster falls into this category, in addition to shrinking the field of view the adaptor corrects for aberrations due to film era lens designs not accounting for digital sensor filter stack. The speed booster also increases telecentrcity, i.e. it makes the light rays strike the sensor more head on reducing vignetting and cross talk issues.

---

So if the claims are true, why hasn't this been done before? Users of APS-C DSLRs have long sought faster wide angle lenses, and teleconverters have been very popular for years.

Well, the problem is that teleconverters increase the backfocus distance, i.e. they cause the focussed image to be projected further behind the lens than it would be without the teleconverter. This isn't a problem as the lens/converter can be moved further from the film plane using a simple tube.

Focal reducers on the other hand (Speed Booster is just the product name of a particular focal reducer made by MetaBones) cause the backfocus distance to get smaller. With a DSLR there simply isn't space for the adaptor, and any optics to increase backfocus would negate any gains in image quality.

However if you take a lens with enough backfocus to accommodate a full frame SLR mirror and mount a focal reducer there's just enough space left for use with a mirrorless camera.

raw - Why are my NEF photos unusually dark in RawTherapee?

I've just started using RAW/NEF files and came across this problem with dark images. I've been reading a bit and I know that an application I open my NEFs with must do some processing to show what camera usually shows on previews. I also know DCP profile files can be used to show the photo in right colors.

As a beginner I've decided to try post processing of photos on a free program called RawTherapee 4.2.73. I'm fairly sure it's not programs fault because I've seen those kind of issues from other people on other programs. I also tried using the DCP profile file (from Adobes DNG converter) but there was barely any change.

Anyways below is an example of two very similar pictures, the left one was loaded for editing thus showing RAW data, and on the right only a preview (only as thumbnail) which is displayed correctly.

So what do I have to do to load NEF files correctly?

UPDATE

OK I'm confused now, I just took another picture and This picture is opened correctly also in RawTherapee. This is the picture (I uploaded NEF to tinypic.com but it got converted to jpg):

I made a picture of Histograms for previous picture that still isn't shown correctly:

Link to full size

From the picture above you can see very different histograms on camera and in program.

One last thing that I noticed is when I took intentionally an underexposed photo, it produced dark greenish NEF, but when I took properly exposed photo the NEF looked pretty normal maybe a bit bleached out.

Thanks!

Answer

I overcame the problem by converting NEF files to DNGs with Adobes converter. And I conclude that RawTherapee just doesn't know how to handle NEF files properly, since AFAIK with DCP profile file it should work correctly.

While this is not a solution to the problem but a workaround, I'll leave an option open for others to solve the problem and this answer will server and alternative solution to help others.

The Solution

I came across THIS post and there was the answer to switch to 14-bit. I just tested and it work great now.

Regards

flash - How to get beautiful even and soft lighting on face?

How do I get bright even and soft light on a face like this?

Image taken from this link

I got the exact same equipment but I wasn't able to reproduce the result.

First I tried lighting it from the side and I got this:

As you can see, it is not even at all. There are a lot of hotspots. Even on the right side where the hotspot is less apparent it is not even.

Then I thought maybe I should avoid side lighting, just like in the original video, I did a traditional clam shell style with a reflector at the bottom. I got this:

It seems to be a bit better, but it still doesn't have that even look.

Any ideas, what I am missing?

About my my setup:

Camera is in manual mode f/9, 1/250, ISO500

That setting avoided most of the ambient light.

The softbox is the exact one in that link. 26″ Rapid Box Octa. It has a deflector plate inside, and a diffuser fabric at the front.

flash - How can I improve the dull colors in my product photography?

I try to shoot some pictures of apparel, lingerie, cometics on a white fluffy rag or a white paper board with a Canon EOS Rebel T2i + a Canon - Speedlite 270EX II External Flash on a tripod in day light in a mostly white room. I want not shadow-less pictures but with little shadows, natural colors similar to from http://www.photigy.com/how-to-photograph-textured-subject-like-shoes/ or

Time to laugh: I spent 3 days taking hundreds of pictures, my back and legs hurt of continuous folding/unfolding. My photos - worthless piece of crap, the camera - crap.

First, with the flash. If it's pointed directly at the object, there no shadows at all, all of them are eliminated, ugly crap. If it is cosmetic bottles, they have disgusting illuminated spots. If the flash is pointed at a ceiling, it is still crap, it doesn't help much. Colors are not natural but very grey, the focus is blurry. Cheap work.

Second, without the flash. Holly molly, absolute crap. I would draw by hand better than taking pictures like that. Colors - dull, no focus at all like in a cheap camera for $100. Only Photoshop helps, and I can resurrect photos.

I tried to make a diffuser of white paper for the flash - didn't help, a 5% improvement.

I tried to shoot under a fluorescent bulb - crap. I bought another $40 bulb of the 3M brand with 1000 lums - it didn't help, yellowish pictures, dull, grey, poor focus.

The camera's settings are auto, I tried manual, set all properties 100 times - the same result like in auto. The manual focus doesn't help, works the same like in auto focus.

Please help.

My masterpieces (not edited):

Answer

This is a big subject, so any answer is going to be incomplete. Entire books have been written on lighting and product photography; if you're interested in a good one, "Light: Science and Magic" is in its third printing, with 234 out of its 277 combined reviews being 5-star on Amazon-dot-com. It's a text on principles, not a photographer's look-at-what-I-did portfolio, and covers a lot of ground. Well worth it if that style of learning appeals to you.

To create useful shadows the flash needs to be away from the camera. An off-camera TTL cable will let you do this; Canon has the OC-E3 cable, but much cheaper alternatives are not hard to find. This will let you move the flash four or five feet (1-1.5m) away from the camera, which will make a huge difference for tabletop photography. You can preview the effects of the flash placement by moving a flashlight beam across your subject, and the difference can be tremendous.

The 270EX and T2i has two exposure controls that you'll need to juggle, and you'll need to be out of Auto mode to do it.

The first is exposure compensation, marked by a +/- icon. A positive value makes the image brighter, and a negative one makes it darker. Use this when a white background or a dark subject dominates the frame, but keep an eye on the highlights and deep shadows when you use it. For example, there's some delicate highlights on the bottle of lube (excuse me, 'Enchanted Nights Ultra Lubricating Hand and Body Cream') that would become ugly if they were much brighter. If you're in Manual mode you set this more directly, by choosing a combination of shutter speed and aperture that's brighter or darker than the central meter position that the camera will encourage you to use.

The second control is flash exposure compensation. This tells the camera how much light the flash should add to the scene relative to the metered non-flash exposure – it makes the flash brighter or darker. A less powerful flash blast can fill in shadows when window/ambient is the main light source, and more power can make the flash be your key light and let ambient light be the fill. This is where you can really change how the photo looks.

Make sure that you have the camera on a tripod while you're doing all of this, and have the flash on a second tripod or on a stand as well. Having a consistent placement makes it much easier to see the effect of small changes and repeat what works. Also, don't do three days' worth of effort before looking at the results. :) I may take dozens of photos before I've dialled in my setup, look at them on the computer to confirm, and then wipe the card before taking the few 'good' photos that I did all of the work for – then repeat it all again for my next setup.

Finally, remember that what you're doing at the camera stage is simply creating the best possible raw material for digital editing. Removing the background, fine-tuning the lighting, and boosting the contrast and saturation is the next step in taking your lube bottle from its present 'American Apparel' advertisement state to a fully-groomed Victoria's Secret runway backdrop. After all, nothing in real life actually looks like it does in the magazines.

studio lighting - How can I photograph a reflective convex cylindrical trophy without reflections?

What I need to do:

Take a standard "Product Shot" of an old trophy/cup with writing on that doesn't look a complete mess thanks to reflections

What I have available to do it:

• Two radio triggered flashes


• Two CFL bulbs on stands


• Large "Light Tent"


• 1m diameter reflector


• ONE white blanket

What the problem is:

I don't have an entirely empty white room to do it in, and the concave cylindrical form of the trophy seems to emphasize any reflections present, including me, the light stands, the camera and any lights that aren't behind the object.

Here is my best shot:

(Yes, it's a little wonky, and the edges look rubbish, but at this point, I realised I couldn't get rid of the reflections without asking for some advice, so I gave up trying anything better for now)

I understand that my reflection would be greatly diminished if I was further away using a longer lens, but the further away I am from the object, the more ground there is between me and it that will be reflected. If I were up close to it, I could put my back against a white wall, the white sheet from the wall to the cup, a white background behind the cup and possibly something white over me and the camera (with lens poking through), but that setup is starting to sound a bit ridiculous.

Is there an obvious setup with the equipment listed above to get the shot I want?

EDIT - should probably mention that this is a museum artefact and cannot be altered, modified or have anything added to it. So any kind of non-reflective coating is not an option.

EDIT - The Winning Shot

As promised, here's the final shot:

And here's the setup I went for in the end:

Not shown in this image is a flashgun on full power pointing at the upper half of the back of the light tent. The camera is about as low as it can get on my tripod. The sheet mentioned above was clamped to the opening of the tent and bunched up around the lens. Focal length was 13mm (efl: 20.8mm).

The lens is still visible in the image (that ugly black blob), however, this was shown to the client and they were more than happy with the result. I suppose not wasting a client's time and money striving for perfection - when pretty good will do just fine - is a lesson in itself!

The "correct" answer is the one that matched my setup the closest, as the solution I went for was the easiest and cheapest, given what I had to hand. However, anyone reading this because they want to do something similar should read ALL the answers, as there is great advice to be found in each.

Answer

Round metallic subjects inherently reflect all of the surroundings, and the camera will always appear in the reflection. The best you can do is control the environment to make it reflect what you want.

If your studio is large, lighting only the subject, and making sure the camera and surroundings are dark may be sufficient. Black cloth or paper with a hole for the lens can help conceal the camera.

Another possibility is to set up a light tent: completely surround the subject with white material, light it via diffusion through this material, and photograph it though a small hole for the lens. Undesirable seams or reflections should be minimal and easily removed in post. Premade light tents are available in a variety of sizes from photography retailers, or you can make your own.

Finally, using a long lens to try reduce the size of the reflection will work only for reflections in curved subjects; reflections in flat subjects will remain the same size. The camera's own reflection can in general be controlled by keeping it in the dark, or by putting the subject in a light tent with only a small hole for the lens.

macro - Image Stacking for macrophotography

I'm planning to buy an image stacking software for macro photography. I have been trying to figure out the appropriate software to stack images if the photos are clicked handheld.

I understand that the best stacking happens when the camera is on a support. Is it high time to buy a tripod or there are softwares that can help me for handheld shots?

Note: I'm familiar with Helicon Focus.

post processing - What is an efficient workflow for picking photos from a large set?

In the last couple of days I shot quite a number of images at several locations (been to a concert and conference in another city). Now I wonder how others process large amounts of photos.

Do you first go through from first to last and rate, delete, tag, label, adjust metadata etc. for each image? Then crop/adjust? When do you put titles/caption - if at all - onto you images?

I'm really having a hard time figuring out an efficient workflow as I want to have my library and metadata as complete as possible. I tend to get stuck at one image that I'm not sure if it's a keeper while adjusting levels etc.

I use aperture, but I think this should be rather software agnostic.

image quality - If I want to shoot darker shots, is it better to increase the lighting and then darken in post to retain clarity?

I'm just getting started - in my last shoot, I was using a 6D with a 50mm/1.4. In low light, the pictures looked fantastic on the viewfinder but on the computer screen, appeared extremely grainy.

For future shoots, if I want to achieve something like this:

Should I shoot with way more light / lower ISO to retain clarity, and then just darken in post? What kind of setup would be needed to achieve the above?

With my setup -

Camera Canon EOS 6D

Lens EF50mm f/1.4 USM

Focal Length 50mm

Shutter Speed 1/40 s

Aperture f/1.8

ISO/Film 6400

I was getting very grainy results that I had to soften in post (in case you want to see my attempts):

https://500px.com/MICKBEN/sets/best-of

Any tips would be much appreciated.

Answer

The look you are going for is known as low key lighting. It is not necessary for the room to be dark. You just need to put enough light on your subject that there is a large enough difference between the shadows and the highlights.

I took this self portrait by shooting into a mirror in a fully lit room. By using a good amount of flash power I could use a fairly narrow aperture at a low ISO setting and a moderately fast shutter speed. There was a black curtain about 15 feet behind me. The only difference here is the direction of the light with reference to the lens' optical axis, and of course full color instead of monochrome. For my shot it was at about a 45º angle to one side and also a 45º angle below my subject. (Me!) For the example on the question it is at about a 90º angle to the side but at the same height as the subject's face.

For that kind of work, ISO 6400 is awful high with any camera. You're going to give up a lot of dynamic range as well as detail (via the noise reduction required) when shooting at such a high sensitivity. Here's how dynamic range drops off in the 6D as the ISO setting is increased. (As tested by DxO Mark here. To use the link you'll need to click on measurements-->dynamic range-->screen to view the info shown below). I've included the 5D Mark III in the comparison because it is interesting that the 6D seems to have tested at about a 1/2 stop advantage in terms of DR, even though the SNR tab shows both have near identical Signal-to-Noise Ratio curves.

Here's the SNR tab from the same link above.

Although I haven't used the 6D, I find that with my similar 5D Mark III, ISO 1250 or 1600 is about as high as I want to push it in a controlled environment. When an image is properly exposed at those setting, noise is very manageable without too much loss of detail. And there are not really many reasons to ever push it that far. ISO 800 and below are very clean on the current crop of Canon EOS FF bodies.

If you can add light to lower your ISO at least a couple of stops then that is the best solution. As you add light to your subject and reduce your ISO you can keep the background dark by shading the background from the light of the flash and closing your aperture if needed. If you are using f/1.8, try f/2.8, f/4, f/5.6, f/8, etc. until the background is dark enough. With normal flash, you can't shorten the shutter speed beyond your camera's sync speed (1/180 sec for the 6D) without one of the shutter curtains blocking a portion of the sensor when the flash fires. The main concern isn't how dark or bright the scene itself is, but rather how much difference in brightness there is between the subject and the backdrop.

If you can't add light, then if the camera isn't already on a tripod put it on one and lengthen the shutter speed enough to lower the ISO a couple of stops or more. In that case you will probably need to pull the shadows down when you edit.

And just another tip when selecting an ISO setting: In general, when you are concerned about noise you should probably avoid the + 1/3 stop ISO settings (125, 250, 500, 1000, 2000, etc.) with current Canon EOS cameras. This is due to the way EOS cameras adjust for ISO settings not 100 x powers of 2 (i.e. 100, 400, 800, etc). Some tests show less noise at ISO 1250 than at ISO 125!

What can be done using a 18-55mm lens?

I have a Canon EOS 1000D with 18-55mm kit lens (entry level, as many say). Whenever I go out for a shoot, I always end up feeling handicapped because of the limited zoom range.

Most of my friends keep suggesting I get a 'good lens' sometime. I agree on the need for a long range lens, but I am not quite ready to quit on this lens just because of the zoom range. And I am also sure that good photography would still be possible with an 18-55mm lens.

I have tried shooting flowers, close-range portraits, still-life and I liked the photos it gave.

I need pointers about where this lens is most useful. How can I make it work wonders ?

Answer

What can be done using a 18-55mm lens? I have a Canon EOS 1000D with 18-55mm kit lens.
I agree on the need for a long range lens, but I am not quite ready to quit on this lens just because of the zoom range. I have tried shooting flowers, close-range portraits, still-life and I liked the photos it gave.

I need pointers about where this lens is most useful. How can I make it work wonders ?

All text in blue <- like this, is linked to images - whether or not thumbnails are provided.
Thumbnails are not live linked.

All these things can be done with your kit lens:

• 
  

  Learn to minimise depth of field in a given situation (max aperture, max zoom, foot zoom to fit) to see how much background defocusing you can achieve. Not an ideal lens for this but results will please you. Try selecting between two objects in mid distance but at different distances. Can you get pleasing differentiation.

  
  


• 
  

  Set lens to minimum aperture. Use tripod or place camera on a wall etc. Take photos at night of street lights etc. Note halo/coma effect. What photos can you [produce using this.

  
  


• 
  

  "Through the bars": Find some "bars" - birdcage etc, put front lens element almost touching bars
  
  (as close as possible). Experiment with what you can achieve.
  Can you make the bars vanish? How can you use this ability?
  Larger version of "through the bars" here / thumbnail below:

  
  

  This was taken through cage bars. Can you see them?
  That used a 50 mm f1.8. What can you achieve?
  This photo was taken through a heavy mesh as seen here at f6.3.

  
  

In both cases this is achieved by placing the lens front element as close to the bars or mesh as you can manage so that they are well inside one focal-length of the lens centre and so are dispersed rather than focused. Your kit lens can achieve this same result allowing to to produce pictures of apparently uncaged beasties or birds or ... .

• 
  

  Super Macro: Do you have ANY other lenses. Using even an old lens from another camera that does not fit your mount, set spare lens to "wide open", invert so front elements of it and yours are adjacent and almost touching. Maybe tape together. Now point at something small and very close and well lit. Note massive macro effect possible. Experiment with focal length setting on each lens.

  
  


• 
  

  Set to small aperture, low ISO. Tripod or brace and photograph falling water and fountains.

  
  


• 
  

  Set to small aperture and low ISO and use flash. Photograph fountains that have streams of drops or blobs of water in the air. Experiment with flash level and ISO. Be amazed.
  Like this fountain shot - f/6.3 at 200mm, but your lens can do similar This used no flash. Add flash and use a smaller aperture and the background will darken or even vanish - jewels of water on "satin background."

  
  
  


• 
  

  Small aperture, low ISO, exposure compensation up. Photograph people when standing close to them looking slightly downwards with large area of roomlight lit carpet etc behind them. ie camera sees target lit by flash plus even carpet etc area behind in distance and not well lit by flash. Play with exposure until person is well lit for a nice portait but background drops away to almost blackness - even in a well lit room - and no photoshopping.

  
  


• 
  

  Do you have rear curtain flash? Experiment at night with people with lanterns and flashing lights etc.

  
  


• 
  

  Fun shots like this hair and water shot do not need special lenses etc - just lots of patience.
  (It took about 12 trials to get this right.)

  
  
  

  

  
  


• 
  

  Silhouettes - bright background, dark foreground, expose for bright. Even higher contrast than this can be easily achieved.

  
  


• 
  

  Lie on the ground like this, stand on chairs, climb trees, move in close,
  lean out of windows and trains
  Maybe like this - BUT carefully! !
  find interesting angles.
  
  None of these need special lenses but all add interest. This or this or this or this or this or this or this or this or this or you get the idea

  
  

etc - the aircraft is actually at 100 or so feet above the ground,
can be done with the kit lens.

17mm - Ham it up.
"Oh Mater ..."

Link to this answer: bit.ly/18-55kitlens

nikon - Will my SB-600 work off camera with any camera?

I own a Nikon SB-600 flash and no camera. Now, looking for a new camera, I want to know if I could trigger the flash from another non-Nikon camera body.

I never use it on camera and therefore I think I have two options for off camera triggering. 1. trigger by flash 2. trigger by a remote control device (e.g. Cactus or something cheap )

Questions:

1. Will flash triggering work?


2. can I put transmitter on, lets say panasonic camera and sb 600 receiver ?


3. Can the flash be mounted on other camera brands?

Answer

You cannot trigger it by flash. The SB-600 does not have an optical slave mode. You can buy an inexpensive optical slave trigger though and trigger it with the built-in flash on your camera.

You may be able to mount it in the hotshoe of a non-Nikon body, but it may not fire. In fact, it's possible it could damage the camera. Nikon flashes use 12V trigger voltage, and some cameras, like Canon, use 6V). There is some information here - Strobe Trigger Voltages

You can certainly trigger the SB-600 using a radio trigger, such as the Cactus, from a non-Nikon body. Whatever trigger you choose, you just need to make sure it's compatible with both the flash and the camera. The Cactus is compatible with the SB-600.

lens - Is it a wise-decision to buy full-frame lenses for use on an APS-C body?

I have a Canon 550D which I've been using for around a year now. I really love it and have learned a great deal with this and the 18 - 135mm kit lens. But now with experience I feel the need to get some better glass. I won't be buying a new body any time soon because I figure investing in some good glass is more important.

As I have looked around, I see quite a few good used L lenses I can get in ebay for good bargain prices. But I know that the EF lenses don't have the same focal length in the cropped sensors. Is it a wise decision to buy these EF lenses or buy the cropped sensor alternatives?

I have the following lenses in mind that I am looking to buy down the line from the canon range over the next several months.

16-35mm f/2.8L, 24-70mm f/2.8L, 70-200 f/4L.

Are these apt choices for cropped sensors? I know most pros with FFs use these but I am a bit skeptic that they will serve the same purpose for me. If so what are the alternatives for this that have almost as good image quality?

camera settings - As an inexperienced user, how can I best take action photographs with a DSLR and consumer superzoom?

I have a Nikon D5100 with a Sigma lens 18-200mm. I need to take fast action pictures of my grandson playing baseball, in short stop plays; this is a very fast position. What would be the best setting I should use without any blur?

equipment protection - What are the dangers of removing a lens while the camera is on?

The manual warns that you should turn the camera off to remove the lens, but it doesn't say why.

I suspect this may have to do with dust, but I could imagine there are lots of other reasons. I'm hoping someone can tell me the reason for doing this, so it will help me to never forget :-).

Answer

When I get this question from my students, the underlying question is often based on the persistent myth that taking a lens off without first turning off the camera will 'fry' the lens, the camera, or both (depending on who you talk to).

With both Canon and Nikon cameras the leftmost pins on the body (when looking at the camera) are the VBat (6 volt lens power) pins, so when the lens is disengaged and rotated counterclockwise the first thing that happens is that power is removed from the lens. Since none of the other lens contacts sweep over the VBat pin, that scenario is actually physically impossible. Additionally, since the lens power is disengaged from the moment the lens is rotated, the lens is no longer able to pass information back through the communication (dcl and dlc) and clock (dclk) pins. Thus there is very little danger of bad data getting passed between the camera and the lens and somehow 'corrupting' anything unless you really snap the rotation of the lens and there "happened" to be communication going on at just the right moment. In any case, simply turning off the camera and turning it back on would clear such an error.

While I have no direct experience with the pin and contact patterns of other brands of SLR/dSLR, I would be very surprised if the others (Sony, Pentax, etc.) did it differently.

backdrops - What surface to use for food photography?

Most of the photography I have been making recently has been for my Cooking.Stackexchange blog posts. I have run into some problems when choosing a surface to put the food on. Maybe somebody can suggest a better idea?

This is what I have used so far.

• Glass, frosted on the underside. This is what my dining table is made of. I am not too good at lighting, and the glass is practically unmanageable for me. While I have had some serendipituosly good pictures with great reflections, most of the time the results are bad. Looks weirdly green from some angles.


• an unrolled window blind, pale yellow. Sturdy thing, but if it gets a wrinkle once, it is hard to straighten it again. If liquid or powdered food is spilled on it, it is hard-to-impossible to clean during the shoot. Way too narrow for many compositions.


• Plain cheap off-white cotton fabric. Wrinkles a lot, can't be cleaned. Color not too great, a bit "dirtyish".


• MDF plate laminated with white melamin. This is what I currently use. Can't be folded/rolled for storage. The white melamin reflects colors from its surroundings - it creates no visible highlights in the picture, but when setting the white balance, I can either make the melamin white/grey (I don't have the equipment for even lighting) and give the food a slight off-color, or keep the food color and have a color cast in the background. The white surface is also a bit too even for my taste - it looks like I am trying to achieve a "no background" effect and failing. This is an example of what my pictures look like with it.

• a colored place set mat. It doesn't have the problems of the melamine plate, but when I shoot from an unusual angle (and I do that a lot for closeups), the geometrical pattern of the weave shows that the angle was weird. It is also moire-prone when resizing. The vivid color gets reflected in gleaming white porcelain plates. And the mat is way too small. An example, complete with bad angle:

• 
  

  A black silicone dough-rolling mat. Washing leaves droplet shapes on the matte surface, and they are hard to buff away from silicone. Dust is way too visible on it. Also, it looks like I am trying to achieve a "perfect black" background and failing. It is also too small. And many foods don't look good on a black background.

  
  


• 
  

  Arranging the food on a wooden cutting board. It looks natural for food, but the pattern is strong enough to be distracting (I ended up covering it with a napkin). Also, when the whole board is in the picture, I have to align the camera perfectly, else the sides of the board are not parallel to the sides of the photograph, and using the transformation tool only helps to a degree. This picture was made with the cutting board on the glass table, you can see the weird geometry and the greenish color of the glass.

  
  

Can you recommend a surface which doesn't have these disadvantages? It should be easy to stow away (I can't afford to keep a fully built-up setup all the time), reasonably cheap, and look good. I need it to be big (my melamin plate is about 100x80 cm and I hit its limits when I shoot from shallow angles). No strong colors, and it shouldn't reflect much. I would prefer some subtle irregular pattern, not a uniform color. A slight neutral color would be good - pale cream or yellow is OK, but I am considering a light neutral grey so I can measure white balance off it (when I shoot with natural light, it is too much work to make a greycard picture every time a cloud moves in front of the sun). And I must be able to easily clean it from spilled food during a shoot. Something pliable (so I can construct a makeshift seamless background) would be nice, but not necessary.

I guess the perfect surface doesn't exist, but if you can come up with ideas which match most of those criteria, I would be very happy.

Edit The "easy to clean" criterium is non-negotiable. I want to place a juicy berry directly on the surface, or a stack of cookies. When I move them around, I want to be able to wipe off the resulting juice stain resp. grease stain without much effort. This makes paper and fabric a bad choice for a "main" surface. (I am aware that I can temporarily use napkins under plated dishes, but I am more concerned about a "generic" surface right now). Also, I am pressed for space, so, I am looking for something which will look reasonably good in most situations, as opposed to a selection of surfaces which look great in a narrow range of situations.

macro - How can I calculate the change an extension tube makes to the maximum magnification of a lens?

Possible Duplicate:
How can I calculate what the effect of an extension tube will be?

My understanding is that extension tubes increase the magnification of lenses by reducing their minimum focusing distance.

But I can't figure out how to calculate the change an extension tube makes on to the maximum magnification of a lens. Is there a formula of some sort I can use?

Answer

This is a question that would have been simple to answer in the '70s, and there's still a relatively simple answer for unit focus lenses (lenses where the entire optical group moves as a unit when you focus -- with, perhaps, the exception of one or two lens elements that float within the group to correct aberrations for close focusing). By far the vast majority of currently-available lenses, though, are internal focus.

Internal focus lenses actually change their focal length when you focus -- the lens gets shorter as you focus closer, so the front element(s) don't have to move. The closer the lens focuses, the shorter the minimum focal length of the lens becomes. You need to find out what the actual focal length of the lens you are using is going to be -- and unless it's pegged at infinity, it probably won't have much to do with the number printed on the lens barrel or the number you see on the zoom ring.

At a 1:1 reproduction ratio, the distance from the optical center of your lens to the sensor plane will be exactly one-half of the distance between your point of focus (your subject) and the sensor plane.

At magnifications other than 1:1, the distances can be calculated using the formula:

1/sO + 1/sI = 1/f

where sO (displacement of the object) is the distance from the subject to the optical center of the lens, sI (displacement of the image) is the distance between the film/sensor plane and the optical center of the lens, and f is the effective focal length of the lens at the set focal distance, and:

hI/hO = (sI-f)/(sO-f)

(the the ratio of the heights of the image and the object is the same as the ratio between the distances of the image and the object from "infinity focus" on either side of the lens)

They're simple enough formulas if you know the focal length of the lens. With an internal focus lens, you either have to know it (that is, you can get the data from an outside source) or you can deduce it if you focus to the close focus limit on a well-defined subject (something with hard edges), measure carefully from the sensor plane marker on your camera body to the subject, then take a picture and count the pixels.

The size of your sensor and the number of pixels horizontally and vertically are known quantities (they should be in your manual), and your measurement will give you the value of s1 + s2. That should be enough to figure out f -- and once you have f, you know what's really going on between the lens and the sensor, so you'll know how much extra magnification a given thickness of extension tube will give you at the closest focus point. At the furthest focus point (when the lens is set to infinity), the calculation is simpler because you can use the f value that's printed on the lens. It's probably the close focus distance/magnification you're interested in, though, and if you can't find the focal length data for your lens on the intarwebs, you've got to experiment. (And $_DEITY help you if your lens is both an internal focus and a zoom.)

Or you could just buy a set of tubes and try them out.

equipment recommendation - Which lens should someone who enjoys the Canon EF 50mm f/1.8 get next?

I bought a Canon 550D months ago, and at that point I chose the 50mm f/1.8 because it was super affordable and quite popular. I must say I've taken some really wonderful photos with it; mostly with some people in them.

I'd like to upgrade to a second lens that has built-in zoom to take wider pictures. For example, when being in Barcelona, I was unable to take a good shot of the Sagrada Familia because the building was not fitting inside my pics.

Also I would like to take some distant landscape.

What would be the best next lens to get that would be great and cheap like the 50mm f/1.8 but serve a different and complementary purpose?

Answer

Some logical recommendations by price:

If you want to focus on wide angle shots, you may be interested in the ultra wide angle Canon EF-S 10-22mm f/3.5-4.5 USM, which would be suited for that type of photography. If you are interested primarily in long distance landscape shots, one of the fine 70-200mm lenses would be a great way to get into that.

To summarize, I think it is important to note that the Canon 50mm f/1.8 lens provides a great value or bang for your buck. I am not aware of any other lens that really provides that great value for the money in that price range. You may be able to find something used or second hand that has a great value(utility) to you. The options above are great compliments to the lens you already have, but you have to start to make decisions on what you want out of the next lens, what price range, and what trade offs you are willing to make to achieve that.

technique - How do I meter for long exposures (10+ minutes)?

One of my longstanding interests is long exposure night photography.

However, many of the situations where I am shooting require exposure lengths on the order of 10 minutes, which is far beyond what the internal meter in my camera (5DII) can handle.

Right now, I take a test exposure, extrapolate from that to guess my exposure time, try again, etc...

This works, but since the test exposure alone can be 10 minutes, and it generally takes me a few shots to get the exposure right, it can take 30 minutes to an hour just to figure out exactly how long I need to expose for.

Obviously, this is really inconvenient (fortunately, long exposure subjects don't move much, most of the time).

For instance, recently I did a series of 13 minute exposures at f4, ISO125. It came out really well, but I would up spending 2 hours to get one shot.

Anyways, is there an easier way to determine how long an exposure has to be, preferably that doesn't take multiple test exposures? I've looked at light meters, but none of them make explicit statements about how low a level of light they can handle.

Answer

At light levels this low, you'll be much better off by taking some test shots and checking their histograms rather than just relying on a light meter (which is usually optimized for measuring light, not darkness). However, you can make the test shots take less time.

Perform the test shots at the maximum ISO your camera can handle (avoid the uncalibrated expanded ISOs though), and multiply the measured proper shutter time by the factor you decrease ISO for your real shots.

Learn how a histogram's right-hand end for shots underexposed by 1/3 steps, 2/3 steps, 1 step looks like, so you'll recognize them and need fewer test shots.

Take the test shots with widest aperture and multiply measured shutter time by the difference to real aperture squared (another way to say it: multiply by two for each stop you'll be closing the aperture).

For example, if your test shot showed that at f/2.8 and ISO 6400 your exposure should be 8 seconds, then at ISO 125 f/4 you will need to expose for 8 * (6400 / 125) * (4 / 2.8) ^ 2 = 8 * 51.2 * 2 = 819 seconds = 13 minutes 39 seconds.

Note that if you happen to be shooting film, you'll also have to adjust for the reciprocity failure of the film you are using.

photo editing - What Photoshop plugins are must haves?

When you as a photographer edit your photos in Photoshop (after some processing using Camera Raw or Lightroom) are there any Plug-ins/Actions/etc. (free or paid) that are must haves for you as a photographer?

What do they do and why are they so important to your photography, be it workflow or effects?

Answer

I use most of the Topaz Labs Photoshop Plug-in Bundle regularly, and consider it to be one of the greatest bargains available in the world of digital photography at the moment (when purchased as a bundle — and there's a fully-functioning 30-day trial so you can assess them yourself, as with most of the better plug-ins). But it is perhaps worth examining what "must-have" means before making any decisions. And while I use and love the Topaz plug-ins, they aren't the only ones out there by any means.

"Must have" to fix technical deficiencies

Because of the Laws of the Universe, the best expressions in portraiture and the most exciting action in sports are always going to be captured on a frame that has something else wrong with it. Maybe the lighting is off, maybe the only camera you have with you is on your phone, maybe there was a glitch in the autofocus, maybe you forgot to reset an extreme setting you made on a previous photo. But it will only happen with the very best, unrepeatable images.

Noise Reduction

As others have noted, in-the-box noise reduction in Photoshop and Lightroom has come a long way, and recent DSLRs are a lot better-behaved than those of only a few years ago in this regard, what with sensor and microlens improvements and better in-camera noise reduction and all. But I've found Topaz DeNoise to be significantly better than anything else I've tried at reducing noise while retaining detail. Yes, that's a "for now" assessment -- no doubt others will catch up. But whether we're talking about my old D70^† at ISO 1600 or a D3s at ISO 25,600, the highest ISO on the camera that isn't flagged as "special" becomes just another setting; the resulting photos can be indistinguishable from well-exposed shots taken at ISO 200 (or 100 — whatever the base ISO for the camera is). And when you're working with what comes from a compact's 1/2.3" sensor, the results can approach what a "real camera" can do.

JPEG Artfiact Elimination

Shooting RAW isn't always practical either. Whether you're conserving space on a card or need to shoot at your camera's maximum frame rate, there can be very good reasons for shooting JPEGs with a camera that can provide RAW data. And again, there may be times when you're not shooting with your SLR. Or you may be asked to tweak a friend's or relative's pictures. There's no need to pay a huge penalty for JPEG compression (or even huge JPEG compression). While the "remove JPEG artifacts" checkbox in Photoshop does an OK job, it's nothing like as capable as an outboard filter. DeJPEG hasn't let me down yet, and it was one of the things in the bindle that I didn't know I wanted until that "impossible" image came along (I had resigned myself to careful retouching before I noticed the name in the filters menu, and said "what the heck... I can always undo it").

Deconvolution

Minor focus errors, depth of field that just misses being deep enough and lens softness are better handled by deconvolution than by contrast manipulation (like unsharp masking). Adobe recently demoed their own deconvolution/de-blurring filter, and it looks great. Unfortunately, it's not in CS5 and it probably won't be ready for CS6; it's very much at the alpha stage. Topaz InFocus (and other deconvolution filters) can rescue images that are "almost there". (It can also be used to derive detail from images that have significant subject or camera motion, but that's more of a forensic thing — it can cause some pretty heavy-duty ringing artifacts throughout the picture.)

"Must have" for artistic expression

Most of the rest fall into the category of time-and-sanity-saving extras. They become must-haves only in relationship to your stylistic preferences and artistic vision. Many of them can be duplicated (or nearly duplicated) with a little bit (or a lot) of playing around in the host program (Photoshop, Lightroom, etc.); the plug-ins simply make things a lot easier and more convenient.

B&W Conversion

There are, for instance, any number of ways to do B&W conversion in Photoshop. You can simply drop to greyscale, you can select a channel to work with, etc., and manipulate the image colours before doing whatever B&W conversion technique you eventually use. But you'll get the results you want more quickly and more easily with a B&W conversion plug-in that gives you real-time feedback on all of your tweaks. I really like Topaz B&W Effects — the user interface is consistent with the rest of their bundle — but I've also used and like Nik Silver Efex Pro. Either is a whole lot easier than the back-and-forthing you need to do to get the same results in Photoshop alone, and achieving the look of traditional toned images (sepia, gold, platinum, platinum/palladium, etc.) or hand-tinting is an awful lot harder in PS.

Colour Effects

The same sort of thing can be said for contrast (global and local) and colour adjustments. Not so much at the level of correction, mind you, but for expressive purposes. Again, I like the Topaz option, Adjust 5, but I've also used and like Nik Color Efex Pro for many of the same reasons. They're just a whole lot easier, more workflow-friendly and, yes, more fun than doing things the hard way in Photoshop alone, particularly when it comes to things like emulating colour film emulsions, faking toy cameras (Lomo, Holga, etc.) and exaggerating detail illustratively (the one-shot HDR look).

Lens and Filter Effects

Lens Effects can be a lot of fun to play with, and a great way to make the most of images that have distracting backgrounds or too great a depth of field. Like AlienSkin Bokeh 2, it will let you apply very realisic and progressive lens blur to various parts of the image (you get to set the number and curvature of the iris blades, the "creaminess" of the bokeh and the speed of focus transition). You can also simulate vignetting, pinhole cameras, LensBaby-style tilt/shift effects, fisheye barrel distortion, light leaks and so on. You can also "use filters" ex post facto, like graduated ND or polarizers (for blue-sky deeping, not reflection control) as long as the data are there in your image. It can let you "use" cameras you don't have or make lens or filter choices you wish you had made when you took the picture. It's not exactly a do-over, but it's as close as you can get in the real world, and it's a lot easier than doing the same things in Photoshop alone.

Masking

If you do any compositing, you'll know that masking is a geniune pain in the posterior, especially if you need to handle transparency and translucency. A good masking plug-in can make the process something you can easily tough out instead of something that makes you want to dial 911 (or 999, or whatever is applicable where you live). The edge-aware tools in the latest versions of Adobe's products are immensely better than what has gone before, but they're still not quite as easy to use as the better masking plug-ins. I really like Topaz ReMask 3.2, but OnOne Perfect Mask is also an excellent tool (as was UltiMatte/Corel Knockout in its day). In addition to compositing, they can make selective application of other filters and adjustments a whole lot quicker and easier.

Alterntive Sharpening and Local Contrast Enhancement

I happen to like the results I can get from Topaz Detail compared to other sharpening techniques. There's just more simultaneous control over more aspects of detail enhancement/reduction than you get with the built-in tools. Being able to work selectively at levels I'd call "shape", "detail" and "texture" (Topaz calls them large, medium and small details) can make both general and output image sharpening a lot simpler -- it's a lot easier to emphasize what you think is important in the image.

Detail Reduction and Abstraction

I have found less use for the Clean and Simplify plug-ins, but I can see why other people might find them useful. You would have to decide for yourself, based on your own artistic inclinations.

Try 'em, then decide

Almost all of the high-quality commercial plug-ins have a fully-functioning trial available for download. Which ones you'll find merely useful, which ones are distracting toys, and which are must-haves depends entirely upon your photographic style, your artistic vision, and the holes in your personal arsenal of photographic weaponry (and there will always be one). And there is much to be said for having the ability to salvage pictures that are either otherwise excellent (or important) but which suffer from some technical imperfection that make them less than desirable as they are. You won't know what plug-ins can do for you until you've tried them yourself on both your best and your worst images. You might just be amazed.

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^{† Don't laugh — it will sync with strobes at 1/8000s and with i-TTL flashes at 1/500 because it's a CCD camera that uses a hybrid shutter. The focal plane (mechanical) shutter never goes faster than the X-sync speed; it's always fully open during the exposure. 6MP and a low maximum ISO is a reasonable trade-off in a lot of situations, considering that I can use full-power flash at 1/1000s or higher with a lot of flash heads. No ND filters, no loss of power using high-speed sync. Great for web work, and prints up to 8x12 inches look pretty darned good if you're not using a loupe.}

What makes the focus ring on a lens go smoothly?

I’m curious about the smooth movement of the zoom or focus rings on a lens. How is the smooth movement done? Is there some kind of liquid with high viscosity? That doesn’t sound very probable. On the other hand, I have no idea how to get the smooth movement by purely mechanical means. Please enlighten me before I go disassembling my lenses. :)

Answer

The twisting motions you apply to focus and zoom rings are converted to forward and backward movement by helical threads and tracks cut into the barrels inside the lens. This photo shows an example of the threads that do the focusing duties in a partially-disassembled Nikkor prime:

Note the tracks cut into the inner barrel and the metal rails in the outer one which force the inner one to slide forward and back. Zooms that don't use a push-pull mechanism do something similar with less-dense threads so you don't have to rotate the ring many times to get through their entire range. (This technical illustrator's site has some excellent examples as well.)

High-quality lenses have precisely-cut metal threads that fit together with very tight tolerances. A very light coating of viscous grease provides smooth travel and the drag that we tend to associate with "quality." Less-expensive lenses forgo the metal and instead rely on molded plastics. This isn't always a bad thing; many auto-focus lenses had to sacrifice the feel and keep weight down as a way of reducing the load on focus motors to make them work faster.

If you're interested in seeing how all of this works without taking your lenses apart, order a service manual or ask a repair shop if they'll let you browse through one. Most show a complete tear-down of the lens and the illustrations will give you some idea how all of the parts work.

technique - How can I improve stitching of nadir and zenith shots in 360º hemispheric panos?

I am trying to implement full hemispheric panos as a product for Realtors and for another project I am working on, but am having problems with my software stitching the zenith and nadir points. My equators look good, but the stitching gets weird on the z-axis, especially if I'm outside and the sky is solid blue. I think the software gets lost in solid color and makes assumptions.

I am using a Nikon D700 in portrait on a Really Right Stuff pano-head. I take a series of shots, overlapping of course, both in x and y axis. I do have my pano head set so the point of axis revolves around the point of focus withing the lens, so I've got that going for me.

I am using PTGui and Photomatix Pro for stitching. Any suggestions? I am looking for workflow both in field and in the digi-darkroom.

Here is a messy test shot...

And another... Notice the black band at the bottom, this is my tripod head nadir incorporated into the pano. Also notice the funky sky with multiple solar flares. Ugly. Just plain ugly.

Answer

I have been shooting 360 equirectangular panoramas for quite some time now and when I started shooting them I had literally no idea how to go about taking them. Thanks to the Flickr community, however, I managed to master a really simple technique and an effective workflow.

Here are some examples of my panoramas:

First of all, the most important thing to consider in panoramic photography is the lens. The wider the angle the better. I shoot with a Sigma 8mm fisheye on a DX format DSLR and I think this is the best lens to shoot panoramas. If you use an 8mm fisheye lens on a FX (full frame) camera, the lens will deliver a circular image, which is even better, but as you know FX cameras are way more expensive than DX format ones.

The greatest advantage of a fisheye lens is that you can shoot a 360 panorama with only 4 to 6 images (depending on the overlap) instead of taking two or even three rows of pictures. Secondly, an 8mm fisheye lense offers a 180 degree horizontal field of view, so if you put your camera in a portrait orientation you won't have to shoot nadir and zenith separately as your lens will capture everything from top to bottom, so the zenith and nadir will form together from your stitched pictures. That solves one of the problems you have mentioned above.

Next thing to consider is your camera and the settings. You have to remember that you are capturing literally everything around you so you have to be extremely light-aware. As you may already know, you have to put your camera in 'Manual' and make sure you lock the shutter speed, exposure, ISO, white balance and, in some cases, even focus. That way, the amount of light will be exactly the same in every picture.

Shooting against the sun is inevitable in panoramic photography so you will always get some amount of lens flare even if the sun is partially covered by the clouds or your lens has special anti-flare coating. However, do not be afraid of shooting against the sun. I personally prefer shooting panoramas when there is no clouds in the sky as I can capture the whole sun. You can eliminate annoying flare in Photoshop by cloning or content-aware fill in CS5 (believe me it does a great job) or you can use the flare creatively.

Next, you have to remember that in terms of vertical field of view you are capturing a scene that even a human being cannot entirely see without moving the eyes up and down and your lens (a fisheye for instance) captures all of it without moving. Therefore, the picture will be unnaturally distorted closer to the top and bottom, especially if you are standing close to some object. In your third pictures, the stones at the bottom of the picture are distorted and the clouds in the sky as well. This is caused by an extreme angle at which the light reaches the edge of the lens and you cannot change it. I always crop my pictures for esthetic reasons. If you want to have a full uncropped equirectangular panorama then you have to select your nadir carefully, preferably a featureless area without any objects.

Finally, the gear, technique and software. I used to shoot my panoramas using a Nodal Ninja panoramic head but after a while I got really tired of carrying it with me and assembling it whenever I wanted to take pictures. Secondly, a lot of places (especially museums, and galleries) have a ban on tripods. The answer to that is a technique called 'the virtual tripod' and you can read about it here. This is a really effective technique and provided that you have a steady hand you can achieve excellent results. I personally prefer to attach the string to a weight resting on the ground instead of using a pendulum. Also, I use a 3-axis bubble level with my DSLR.

Many people argue that for professional pictures you have to use a panoramic head as the quality is better and there is no stitching mistakes. Well, maybe it is partially true but when you are using a panoramic head the tripod becomes an integral part of your pictures. There is of course a way to shoot nadir and zenith with a tripod to eliminate it from the picture but believe me it is extremely complicated and involves moving the whole tripod several times. I think that with the virtual tripod you can achieve excellent results and then you can spent the time it takes you to erase the tripod from your picture to correct any possible mistakes.

In terms of software, my personal favourite is called 'Hugin". It's a free open source panorama stitcher that has a great community of users and you can get it from here. There is a number of tutorials you can watch in order to learn how to use it. I have been using it for over one year now and never had to use anything else. Additionally, I also noticed that Hugin does a great job at removing people and moving object that can create ghosting. It also can set the control points for you and there is a variety of different projections to choose from such as stereographic, equirectangular, cylindrical, trans mercator etc. Moreover, you have a great deal of control over your panorama as you can adjust the centre, field of view, the horizon, size and much more. Finally, it creates good quality TIFF files that can be further edited. I use Lightroom 3 to work on my panoramas and it is a must have for every professional photographer.

All the best and good luck with your photography

Greg