Category Archives: Tests

Equipment, Ideas, Technique, Tests

Experiment #1: What do you see?

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(Update July 30, 2011: Since the original test was published quite a while ago, I have added this link to the outcome of this test. Of course, if you want to give the test a try yourself, you should read the whole article, try answering the questions, and only after that come back here to follow the link to find out how your response compares.)

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… ;-)

(Note on 9/10/11: Especially on flat-panel monitors, the position of the image on the screen may create visible differences that are not in the source images. Try to view the samples in the same location on your screen to avoid being misled by this. Once you make your observations and read comments here and in the follow-up post, you may see that others noticed and commented on this.)

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

Commentary, Equipment, Tests

Canon EOS 5D II: Early Observations on Image Quality

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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.

(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!

Equipment, Tests

An Example of Corner Performance on the Canon EF 24-105mm f/4 L IS

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Sample24105f16Corner.jpg
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.

Equipment, Tests

Using Prints to Test Four Canon DSLRs

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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.