Today I read a claim in a photography forum thread that “some 17-40’s are soft on the long end.” Having not noticed that on my copy I went back to some test shots I did earlier this year to compare sharpness at 40mm and 24mm with this lens.

The two images below are 100% crops – in other words, they are very small sections of a much larger print that would be something like 5 feet wide if printed at this resolution! The crop came from an area just below the center of the frame. Both were shot on a Canon 5D a 1/125 second and f/11. The camera was on a tripod and I used mirror lockup and a remote release. Both were converted from RAW using ACR with no adjustments to the original settings. The same sharpening process was applied to both.

24mm:	40mm:

My verdict? There doesn’t seem to be a lot of difference in terms of sharpness. And if there is a difference, it would hardly be significant in even a pretty decent sized print. I don’t think a difference would be noticeable in a 12″ x 18″ inch print, and frankly I doubt that anyone would notice even at a larger print size.

What do you think?

There is one other possibility. The person who posted the original message claimed that “some” copies of this lens exhibit this problem. There is no way for me to rule that out with only one sample.

One other related idea. Any zoom lens is going to perform differently at different focal lengths, and there will likely be some focal length or focal length range in which the “quality” may be measurably “best.” But this doesn’t mean that the other focal lengths are not good – in some cases so good as to provide virtually the same quality.

G Dan Mitchell Photography
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