On sharpness, megapixels and lens testing

2007-09-08 • SEND FEEDBACK |
Related: lens testing

I recently made some group photos (teachers and students) as my kids began their school year. I have several observations as I look at the photos and make prints.

Image quality of theCanon EOS 1D Mark III [buy one @AMAZON] is very pleasing, and prints are excellent. I love the time-saving feature of ready-to-print images—I just don’t have extra hours in the day to work on “post”. Yes, each image could benefit from tweaks, but with all my previous cameras I wasn’t particularly happy with the default results, at least not on a regular basis. With the Canon EOS 1D Mark III, I know I’m going to get something good with little or no effort in “post”. See my July 22 comments on the 1D Mark III (and Zeiss glass).

Resolution—though image quality is superb with the EOS 1D Mark III, it’s still a 10.1-megapixel camera; resolution of individual faces becomes a concern with 20+ individuals. My feeling is that for a group of twenty, an 18" print is about the limit for professional-quality detail in an individual’s face—perhaps 24" if the group is optimally-arranged. Often the shot ends up having a wide aspect ratio, leading to even smaller faces. Such situations are one argument for a higher resolution camera such as the 21 megapixel EOS 1Ds Mark III.

Optical quality is also an issue. I used the Canon EF 16-35mm f/2.8L II zoomed to about 27mm for my group shot, and I was disappointed to see blurring and color fringing towards the edges. This is especially annoying on the EOS 1D Mark III, since it’s not even a full-frame camera (1.3X crop). The 16-35mm f/2.8L II cannot “hold” depth of field near the edges, something often overlooked when comparing lenses. For group portraits, blurry or red-edged persons at the frame edges does not look fully professional. It’s a good thing that Canon’s Digital Photo Professional will soon offer the ability to eliminate color fringing.

The confounding thing is that resolution charts and many test shots make the 16-35mm f/2.8L II appear to be a stellar performer, but real-world shots show that test charts can be like lies, damn lies and statistics. For this shoot I needed the flexibility of a zoom, but I would have very much liked to see how the Zeiss ZF 25mm f/2.8 performed. My conclusions are reinforced by similar disappointments seen in dozens of other shots taken that day. My lens is freshly back from Canon service, and I’m certain from resolution charts that it is performing to its full potential. It is an excellent lens, but I want more—not perfection, just consistent across-the-frame results.