I just got this lens on Wednesday and have been playing around with it, trying to learn how to get the most out of it. I've learned through experience that every lens has its own personality that you have to get to know before you really become confident when using it. As part of this process, I've learned that:
1) This copy backfocuses, relative to my other lenses (requires +200um adj vs. +70 for my other lenses).
2) This lens has some field curvature - my first shots of flat subjects were outright blurry in the middle and sharp starting about half way out to the corners.
3) It's spherically corrected such that the foreground "bokeh" is exceptionally smooth, whereas the background bokeh is, um, not.
I've taken the following shots as a sort of sharpness "torture test", using leafless trees instead of a test chart. Despite the boring, colourless scene, there is lots of fine detail throughout the frame to allow sharpness (both resolution and contrast) to be judged. Focus is on the largest tree in the central portion of the frame. All images were shot in rapid succession without adjusting focus. All shots were processed identically in Lightroom 3.3 (WB adj and my default "S" tone curve).
F2:
http://farm6.static.flickr.com/5258/5540044555_a054235159_o.jpg
F2.8:
http://farm6.static.flickr.com/5015/5540051821_68b8c8e13a_o.jpg
F4:
http://farm6.static.flickr.com/5017/5540640610_6b109e7dea_o.jpg
F11:
http://farm6.static.flickr.com/5019/5540663634_faf18bef8d_o.jpg
In these images, you can see:
1) Purple fringing and resolution loss in the upper corners of the frame at larger apertures
2) Lateral CA in the upper corners at all apertures (correctible in PP, but I haven't done this here)
Overall, I'm impressed with this performance except at F2, where there appears to be a "fogginess" throughout the image. It's possible that this may be a focus error on my part, albeit a slight one. The fogginess is most pronounced at further distances from the camera. F2.8 is much "clearer."
Any insights or comments from other FA*24 owners? Is this fogginess I'm seeing here a matter of technique, or an inherent characteristic of this lens? If it's a technique issue, what do you do to avoid this (aside from shooting at smaller apertures)?
Thanks!