Thanks Sean, you bring up a good point (perhaps not directly or intentionally, but good non-the-less) - all my AF lenses are f/2.8 and f/1.2 (and I shoot wide open in most cases - indoor sports with $#!+¥ lighting) so the very shallow depth of field would obviously make back or front focusing more of a pronounced issue. Recently I haven't been very impressed with the image quality I'm getting from my EF 70-200mm f/2.8L IS USM (surprising considering the great reputation this lens has) or my EF 50mm f/1.2L USM for that matter as well. I can see a noticeable difference at 70mm using my EF 24-70mm f/2.8L USM (very crisp and sharp images) vs. my 70-200 (edges of things are blurry). It also varies depending upon which body I'm using these on; images with the 50 looks awesome from my 5D Mark II, but not as great from my 50D (this goes beyond differences in resolution and control of noise) - additionally images with the 70-200 from my 50D were great, but now that I use that lens primarily on my 1D Mark III they don't seem as sharp anymore.I'm only assuming that the issue is slight back or front focusing - thought it wouldn't hurt to see if AF adjustments were necessary and might fix the issue.


Quote Originally Posted by Sean Setters


From what I understand, microadjustments should be made from the focal length most used on a zoom lens. I think the microadjustment will help at all focal lengths, but you'll have the best results from the focal length you did the microadjustment at.



I'm aware of that, but what about working distance? If I make AF microadjustments to my 70-200 @ 200mm with a Lensalign or some other sort of target at 10-12 feet away will that ensure proper focusing when shooting something at a more typical distance of 60-100 feet away. Or should I be making microadjustments with the target close to say 70 ft away?