Most of my photography these days is wild birds, often from a public hide and inevitably often in flight. I achieve a reasonable degree of success, certainly for my purposes, but I'd like to reduce my failure rate, which are mostly "missed focus" of moving subjects.
I know my "birding" equipment (K-70 + Sigma 150-500mm f/6.3) is capable, when conditions are "right", but a few comparison tests recently suggest that a 400mm f/5.6 (actually a 70-200mm f/2.8 + 2x) might give a better "lock-on" rate on a moving subject. I should probably mention at this point that my "default" exposure is 1/1500 @ f/8 in TAv mode, which is chosen to cope with an amount of subject movement and give a degree of depth-of-field. My "default" autofocus mode is AF-S in spot mode. For in-flight shots, if there's time to make a choice, I try to use continuous autofocus, single point for a more distant subject and multi-point if the subject is reasonably close and against a plain sky. I have these options set up on the User modes so can switch from one to the other reasonably promptly
So, does half a stop really make that much difference to the autofocus accuracy and response, in which case I'll be considering saving (hard) for a faster lens and hope to get lucky second-hand, or is it simply that the smaller image in the viewfinder allows for better tracking on my part? Inevitably, no two "action" shots are exactly the same and the ergonomics of the shorter lens may play a part in all this.
I'll look forward to all the insights and experiences I'm sure I'll receive, the responses on this board have always been interesting and educational
Last edited by kypfer; 08-12-2019 at 01:35 AM.
Reason: spelling