G Dan Mitchell Photography

Yesterday I posted “Experiment #2: What do you see?,” in which I shared six image files comprised of three identical pairs of images and asked volunteers a) whether they saw any differences among them when viewed in their web browsers, b) to describe any differences that they noticed, and c) to try to identify the pairs of identical images. As describe in the original post, all of the images came from the very same source file – e.g from a single exposure – and were processed identically with the exception of one variable that was not identified.

Here are the 100% magnification crops from the three source images:

The differences among them are obviously in the amount of noise that was added to the image. No noise was added to the first image – any noise there was in the original capture. 10% level “Uniform” noise was added to the second image in Photoshop. 20% “Uniform” noise was added to the third image in the same way.

While I could have varied camera ISO to produce actual camera-generated noise, doing so would have also produced other variations in the images that would have given secondary and possibly misleading cues as to the differences between images. This most certainly would have affected part c) of “the question” as outlined above. While recognizing that noise added in post is not going to be exactly the same as noise produced in camera, I did try to ensure that the noise would at least be of a type and level that would clearly cause concern if the camera did produce it.

The soft photograph was chosen to avoid masking the noise with a lot of other sharp detail – this image provides very smooth gradients from black to white, where noise is typically easier to detect. I also chose this image because it is nearly – but not quite – monochromatic. This meant that I could increase the effect of the noise by using color noise rather than limiting to monochromatic noise – and that the color noise would tend to be more visible against the nearly monochromatic background.

While quite a few folks reported that they didn’t see any difference among the image when viewed in their web browsers – and, frankly, this did not surprise me – some did report noting differences. Test subjects have been known to both correctly identify real differences… and to think they have seen real differences where none existed. With that possibility in mind, I was interested to see how accurate the “perceptions of difference” might be, hence the challenge to find the pairs of identical images. The idea here is that if one can really see differences between images that one should then be able to categorize the images accurately based on those differences. I won’t comment here on whether any individuals were right or wrong, but here are the six images grouped as identical pairs.

No noise added:

10% noise added:

20% noise added:

A good number of readers asked, “What is the point?” A few even were upset at a test of something they regard as settled – e.g. that noise and other small artifacts become imperceptible when a large image is reduced to typical web sizes. (In this case each pixel in the jpgs is the average of close to 100 pixels in the original file.) However, I can say for sure that this issue is not resolved in the minds of all photographers nor in the minds of many who are making purchase decisions about cameras for themselves or for others.

My thesis was essentially that very significant amounts of noise that would be clearly visible in large original files at 100% magnification will be indistinguishable from files that have far less noise but are otherwise identical when the files are reduced for typical web site use.

A direct “point” might simply be that if you reduce 21MP full frame photographs containing large amounts of noise to 600 pixel width high quality jpg files viewers of the images on the web seem unable to reliably notice the differences in noise levels. You could reasonably extrapolate from this that if your main reason for shooting photographs is to share them on the web, noise levels in the camera may not be an important decision point for you as you shop. Though you cannot extrapolate the following directly from this test, I believe that shooters who mainly share jpg images or perhaps make letter-size prints will not see any significant image quality benefits from getting really high-end cameras. If noise levels as different as those found in this experiment cannot be discerned then the quite small differences in noise between two brands or models of camera are likely to be completely insignificant in images viewed online at typical dimensions. (If you make very large prints on a regular basis then your issues will be different.)

For my part, even though I created the images, I cannot reliably tell them apart by looking at them! When I look up my record of which image was treated which way I think I can see the difference, but I’m pretty certain that if I had to try to pair the identical images I would be unsuccessful. (Note: if you view the images one above other on this page you will think they are different due to viewing angle differences on your monitor. Go to the original post to see them displayed successively in the same location on the screen.)

(Experiment #1 tried something similar, though in that case the variable was the “sharpness” of the original image file.)

G Dan Mitchell :: Dec.15.2009 :: Equipment, Ideas, Tests :: 3 Comments »

Yesterday I posted a series of three images in a couple forums I frequent along with a request that a few people try a little experiment with them. Here it is for anyone else who would like to participate.

Below on this page are three images presented at a typical web viewing size. The question has to do with what you see when you look at them in your browser. (Please read some additional material further down that explains why you must only look at the photos in your browser for the purposes of this exercise.) Considering all aspects of the presentation of the images, in the end there are three possibilities:

1. all three images seem identical – e.g. there are no perceptible differences among them.
2. all three images seem different from one another – e.g. each is visibly unique.
3. two images seem identical but one seems unique – e.g. one is visibly different from the other two, and those two seem visibly identical

Before you give it a try, there are a few “conditions and warnings.”

• You could easily cheat by opening the files and looking at EXIF or other data. But don’t. Or if you cannot resist, please keep your observations to yourself. I’ll stipulate that you could find differences in file parameters by looking there – but that isn’t the point in this case.
• You should not assume that I am incapable of modifying EXIF and file size and so forth in ways designed to trick those who “cheat” and inspect the files directly. Nor should you assume that I have. Or that I have not. Or whatever… :-)
• The question is not “are they three separate exposures or one exposure,” so if, for example, you think that the water looks exactly the same in all three images that, in and of itself, isn’t relevant to the question – and your assumptions may or may not necessarily be correct.
• The question is not whether this is a good, bad, or indifferent photograph – I make no claims beyond the fact that it is used here as a test image.
• The question is not “what would they look like at 100% magnification?” Interesting question, but here the question is just about what you see in the images as presented.
• If you think that you see differences among them, the followup question concerns the nature of the visible differences. Note that the follow-up question is not “how might the differences have been produced?” Just describe what you think you see.
• There is no “point” inherent in the exercise, though when I explain more after getting some responses you might or might not draw some of your own conclusions. For now, just compare what you see.

(Follow-up observation. Having access to server logs, it is interesting for me to note the percentage of people who share a response versus the number of page views… ;-)

I have set this up so that clicking on each image will open it in a new window or tab – though it is a bit awkward in that you’ll need to manually return to this window after doing so. Once they are open in three tabs (best) or windows you can click between them to compare more carefully if you wish – but do stick to viewing them in your web browser since that is part of “the question.”

After viewing, leave a comment stating which option (1, 2, or 3) best describes what you see. In addition, if you select option 2 you might offer a brief explanation of differences you see. (Again, not analysis of downloaded files please! That isn’t the question and it spoils the “game” for other participants. ) If you select option 3 tell us which one is different from the other two and perhaps what you observe about the visual difference.

Here are the images (Click to open each in new windows if you would like – you’ll have to manually return to this window each time – or feel free to view them here “in line.”):

A.

B.

C.

Thanks for participating!

Dan

G Dan Mitchell :: Dec.06.2009 :: Equipment, Ideas, Technique, Tests :: 30 Comments »

I posted earlier today about increasing availability of the Canon EOS 5D II at places like B&H, so I thought it might be useful to begin posting on some of my experiences with the camera during the couple of weeks (and perhaps a thousand frames) that I’ve had it. Here is a copy of something I posted elsewhere earlier this week, in response to a post concerning image quality from this camera:

I’ve shot with cropped sensor bodies extensively in the past. I have shot with a full-frame 5D for the past two years. I recently began shooting with a 5DII and have done a thousand or so frames with it.

I cannot see image quality problems in my images, even in those that stress the ability of the camera in ways that should produce them if they are there: shooting wide dynamic range scenes, using high ISOs (up to 1600), inspecting at large on-screen magnifications, and making careful prints.

My photos have very low noise all the way through the shadows to pure black, even in some photographs where I’ve pushed the shadows either during RAW conversion and/or via the shadow/highlight tool in post. I’m seeing very highly detailed images with smooth tonal transitions. As far as I’ve seen the 5D II has a rather substantial dynamic range – as reported in a number of tests – and it is at least as great as that of the 5D.

Let me repost a couple of 100% magnification crops that I posted elsewhere from the 5DII.

The first was shot at ISO 100 at, IIRC, f/16 using a 35mm prime with the camera on tripod. The crop is a 100% magnification section from the very far lower right corner of the shot. The dark areas were pushed slightly, too, so if there were noise anywhere it would certainly appear here – but I don’t see it even at this resolution, which would be equivalent to a print width of five or six FEET wide. Seems like pretty good resolution to me! (It also speaks well for the EF 35mm f/2 lens.)

The second example is pretty much a noise “torture test” – it is a very dark section of a much larger image. (Again a 100% crop). It was shot using a 100-400mm zoom handheld at ISO 400 in cloudy conditions. There is some noise in the shot, but that is entirely normal – and this noise would be completely invisible even in a very large print. (The pattern on the lighter fabric near the left side of the frame is that of the fabric itself.)

My observations from 100% on-screen pixel peeping are confirmed by the more important test of printing.

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(If my post has helped you with a purchase decision, making your purchase from B&H through this link will help support the blog. Thanks!

G Dan Mitchell :: Feb.26.2009 :: Commentary, Equipment, Tests :: 1 Comment »

I’m taking the opportunity to use the photograph I posted earlier today to illustrate a couple of technical points about equipment and technique. Here is a 100% magnification 400 x 400 pixel crop from the far upper corner of the photograph.

Not much to look at, but that isn’t the point. At this resolution, you are looking at what would be a small section from a print that is four or five feet wide. Before I explain why I think this is important, some technical information about the image: Canon 5D, Canon EF 24-105mm f/4 L IS, 2.5 second exposure, f/16, focus point was on the foreground tree seen in the full image (e.g. – perhaps 50 feet closer than the subject of this test image), IS disabled, tripod, mirror lockup, remote release.

Some doubt the ability of this particular lens to produce sharp images. This sample challenges lens performance in a number of ways: it is a very low contrast image, the crop is from the far corner of the frame, the crop is not in the focus plane of the photograph, at f/16 the effects of diffraction blur should be just visible at this magnification.

With all of that context in mind, this cropped sample represents quite good performance. This section of the image would be very sharp, indeed, in a print at 16″ x 24″.

This photograph is not in the public domain. It may not be used on websites, blogs, or in any other media without explicit advance permission from G Dan Mitchell.

G Dan Mitchell :: Jan.03.2009 :: Equipment, Tests :: No Comments »

Miles Hecker has posted interesting test results in his Canon EOS big guns image quality shootout:

As some of you know, I am a landscape photographer. I migrated to full frame digital SLR’s from medium format film. I used to shoot 6×4.5, 6×7 and 6×9 film with the end product being prints of 20″x30″ and larger. As such, I chose to investigate only one area of the 5Dmk2 in this exercise, overall image quality or IQ for short. For this test, I decided to construct a still life with a wide range of color, lots of detail and very controlled lighting to obtain what for me are valid results.The test would produce 100% crops for pixel peeping. The final analysis of IQ however would be made using real life obsevers and detailed sections of 16″x24″ and 20″x30″ photographic prints.

What I like about his test methodology is that it eliminates the very difficult issue of normalizing on-screen tests of cameras with different sensor sizes and photosite densities but doing something that I have felt would make the most sense, comparing large prints from the different test cameras. In this case he tested the Canon EOS 1DsM3, 5D2, 5D, and 50D. 

I won’t spoil the fun by telling you the results here, but let’s just say I’m not at all surprised at the results.

G Dan Mitchell :: Dec.21.2008 :: Equipment, Tests :: No Comments »

From Night Photography blog by Andy Frazer: More 5D Long Exposure Tests:

Seattle-based night photographer Brian Chapman has posted another set of 5D MkII long exposure tests, this time all taken at night. Although this set was taken at ISO 400, underexposed, and then pushed during RAW conversion, the results are very interesting.

Brian Chapman’s experiments are essentially a night photographer’s torture test – shooting at high ISO, underexposing, compensating in post, adjusting the image, and including areas of uniform color and luminosity. If you aren’t familiar with real life noise issues in digital photography you might think, “Ugh! Noise.” If you have done night photography and made prints for images like those in the test you might be thinking, “Hey, that’s pretty darn impressive!”

G Dan Mitchell :: Dec.21.2008 :: Commentary, Equipment, Tests :: No Comments »

Although I’m not an expert on the subjects of sports photography or bird photography (or “BIF,” as aficionados write) using really long lenses, I have had some opportunities to pick up some skills in these areas recently. Since one of my photography contacts recently wrote and asked for some advice about using a longer lens to photograph birds, I thought I’d share a bit of what I’ve found to work for me.

First, if I were specializing in these types of photography I would likely use different equipment than what I currently have. For example, I know that many folks find the big prime telephotos to be ideal for their work and some prefer the very large, heavy, and expensive large aperture versions. Great lenses for sure, but not exactly suitable for what I do – so my long lens is a Canon EF 100-400 f/4.5-5.6 L IS. I shoot a full frame Canon 5D. This is a great camera for urban and wild landscapes and other types of photography that I tend to do, but it would not typically be regarded as ideal for the type of shooting I’m writing about today. Something with a faster burst mode might be better for those focusing on this type of shooting, and in many cases the advantages of full-frame might be outweighed by other factors.

That said, what have I learned so far? In no particular order, a list:

• Hit rates can be quite low. If you are the kind of photographer who likes to think a lot about The Shot before pressing the button, or who gets frustrated when not every shot is good – get over it. You are going to take a lot of bad photographs, but you’ll eventually start to get better and to get some good ones.
• 
  Tracking moving subjects takes practice. A lot of practice. In many ways it is like learning a sport – you need to do the thing many times, fail many times, begin to succeed, and learn from the process. The first few times I tried panning with a pack of bicycle racers my success rate was terribly low – lots of shots of rear wheels, tilted way out of horizontal and so forth. Eventually I began to smooth out the panning process, reserve a part of my attention for keeping the camera more or less level. Eventually I had more success when I focused up putting the center of the subject in a certain part of the frame, rather than just aiming and hoping.
• Turning off all focus points except the center AF point can help. I find this to be especially true with birds in flight. Unless the background is clear sky the camera will often AF on everything but the bird. With only one AF point active the trick becomes getting it on the moving bird, but if you can do this you’ll focus on the right subject.
• 
  Sometimes pre-focusing can be your friend. In particular with sports that follow a set path – like bicycle racing time trials – you may have more success by applying your careful analytical skills to setting up a shot. Find a good location, pre-focus on a place where the rider will likely be and turn off AF, begin tracking the rider before arrival at the pre-focus spot, and fire away. This can work with birds in flight, but in practice I find it much less reliable there since the darn birds tend to fly all over the place. However, you can sometimes determine that birds are following a particular route and position yourself accordingly. Along the California coast the birds often seem to follow particular routes relative to tops of cliffs or rocks that extend into the water. Spend a few minute studying this and you may locate invisible “sky trails” that they follow.
• Your camera’s “servo” mode may help in some cases, but it isn’t necessarily a panacea with subjects that really move fast. Sorry, you’ll have to figure this one out on your own. :-)
• Burst mode can be your friend. When subjects move very fast – both in terms of their motion through space and in terms of they own motion of legs, wings, etc. – it can be important to get multiple images. Even the relatively leisurely burst rate of my 5D is very useful. But you still need to think a lot about timing the shots – just holding the shutter down without thinking will result in a very low hit rate. Sometimes it is still better to take just a single well-timed frame. I’ll often put the camera in burst mode but still sometimes only shoot a single frame.
• The longest focal length is not always best. In fact, I don’t actually shoot my 100-400mm lens at 400mm all that often. In other cases I’ll use the 70-200 instead.

A few other perspectives I’ve picked up from using the longer lens and from shooting these wildlife and sports subjects:

• Not all sports and wildlife shots require long lenses. In fact, some of the most interesting shots in both categories can take the opposite approach and use wide lenses.
• 
  I’ve also learned more about how very long lenses can be great for certain types of landscape shots. Although I’ve always tended to think in ultra-wide, wide, normal, or shot tele terms when I do landscape, the first time out with the long lens I got a series of landscape shots that I could simply not have taken with the shorter lenses.
• Developing the high speed thinking that you must do when you photograph highly active subjects can improve your photographic work in other areas. If you are comfortable framing a composition given a few minutes to think about it, trying to apply your composition skills to an image in which everything is in flux will really sharpen your “seeing” skills.
• Working outside of your subject comfort zone – e.g. sports for the landscape shooter – has a bunch of positive effects. Not the least of these is understanding how these other subjects can be handled in a way that is every bit as aesthetically interesting as the subjects you may be comfortable with.

G Dan Mitchell :: Mar.30.2008 :: Commentary, Equipment, Tests :: 1 Comment »