Category Archives: Tests

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

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.

Using Prints to Test Four Canon DSLRs

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.

Testing the Canon 5D II for Noise

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!”

Shooting Active Subjects With a Long Lens

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.
  • The Sprint, Santa Rosa - 2008 Amgen Tour of California
    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.
  • 20080217_5981GDanMitchell.jpg
    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.
  • Fisherman, Winter Surf (2)
    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.

Sharpness Test Updated

I have updated my Sharpness and Aperture Selection of Full-Frame DSLRs post to include the corner crops from the same photos used for the center crops that were already there. Here’s the image I added – see the link for full information.

Corner Sharpness of the Canon 17-40mm f/4 L Lens on Full Frame

Since the question of how the Canon EF 17-40 f/4 L performs across the frame for landscape photography comes up periodically, I have posted an older test photo I made last year (2007) – updated here to include a comparison corner and center sharpness.


Technical data: Canon 5D. Canon EF 17-40mm f/4 L lens. Focal length: 17mm. Aperture: f/16. Shutter speed: 1/60 second. Shot on the tripod with MLU and remote release. If the full image were reproduced at this resolution the print would be about five feet wide. (Not that I’d do that – it is a really boring photograph! :-) In a more typical size print the corners would like very good, indeed.

A 100% crop would not be expected to be “razor sharp” – and we see typical results here. It is impressive to see how well the corner image quality holds up – despite the fact that grass is one of the most challenging subjects for a digital sensor and the fact that this part of the scene was much closer to the camera than the focus point in the center of the scene – i.e. the corner section showing the grass is only a few feet from the camera, and the camera is focused hundreds of feet away on the objects in the center of the frame. (On that subject, I’m convinced that a good number of the reports of “poor corner performance” in ultra wide lenses are actually due to the subjects in the corner being much closer to the camera position than the subjects in the center of the frame, especially when the “tests” are done by shooting actual landscape subjects.)

BOTTOM LINE: What does this tell us, how do we view this in the context of reports of soft corners on the EF 17-40mm f/4 lens, and what does this mean for anyone trying to choose a wide (or ultra-wide in the case of full-frame cameras) Canon zoom lens?

While this lens is soft in the corners when shot wide open, the lens is not particularly soft in the corners when stopped down. If your primary use for such a lens is, for example, shooting very low light handheld wide angle photographs the 17-40 is perhaps not your best choice. (The EF 16-35mm f/2.8 on full frame or the EFS 17-55mm f/2.8 IS on a cropped sensor body could be more appropriate zooms.) On the other hand, if you are primarily interested in subjects that are usually shot at smaller apertures (urban/wild landscapes, architecture, etc.) then the 17-40 can be an outstanding lens – though this is more true on a full frame body than on a crop body, given that you are unlikely to use the smaller apertures on a crop sensor body given the diffraction blur issues there. So, to state it very succinctly…

… the Canon EF 17-40mm f/4 lens is an excellent lens for shooting deep DOF small-aperture photography on a full-frame camera. (It is OK but not necessarily ideal for use with cropped sensor bodies, where I would prefer the EFS 17-55mm f/2.8 IS.)

G Dan Mitchell is a California photographer whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
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Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.

Canon 24-105mm f/4 IS Lens Sharpness: An Example

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