First attempt at some lense tests

[chris.bailey]

Hardly scientific but these three shots are all processed in C1 from Raw and then cropped to 800 px x 800 px with no other adjustments.

28-135 @ 50mm
http://www.pbase.com/image/25158870.jpg

17-40L @40mm
http://www.pbase.com/image/25158880.jpg

50mm 1.4 @50mm of course
http://www.pbase.com/image/25158956.jpg

Shows how good the 50mm is but for close up work at open apertures the 28-135 is surprisingly good.

(IMAGE URLS CORRECTED BY PEKKA: do not use pbase image properties, use the pbase page link and simply append it with .jpg)

[samdring]

so 50mm on a 28-135 is different to a 50mm on a 50mm??

[Tom W]

The point of focus appears different on the 50 mm than on the other two. It focused farther back on the duck's head, while the two zooms focused on the beak. Perhaps you could try manually focusing on the same point with each of the three lenses.

[Jim_T]

What F stop did you use..

That's an important thing to mention when testing lenses.. Most lenses will perform *noticeably* better at f/8 than they will wide open..

Testing one lens at f/8 against another at f/1.8 isn't really fair.

[chris.bailey]

All were set wide open at their respective wideopenness (?) and I used a single autofocus point on the eye. The depth of field is different on them which I do not understand. I did move the 17-40 forward to get the same coverage as the 50mm jobs.

Will have to play further at the weekend

[Tom W]

That explains the out-of-focus beak with the 50 mm lens - the depth of field is shallower at f/1.8 than it is at f/4.0. It would be a better comparison if they were all shot at the same aperture, say f/4.0 or f/5.6.

Something else to consider - don't get so close to the subject that you've reached the close-focus limit of any of the three lenses. I'm not familiar with the other two lenses, but I believe that the closest distance that the 50 mm will focus at is 1.5 feet (about 1/2 meter). So, if you're right at the edge, the lens may be barely able to resolve the subject.