7D AF spot problem

[neuroanatomist]

If the object that you are focusing on is far away, and very small (like the birds head above) and moving slightly, and the background is large and diffuse,and the the lens is not held perfectly still, or is not on a monopod or tripod, then the spot AF and photographer may have a hard time focusing on the subject and the spot AF will have an easier time focusing on a large diffuse background.

This is a common scenario for me - bird surrounded by branches, with the 100-400mm lens at 400mm handheld on my 7D. My settings are Spot AF and spot metering, and I prefer to use an off-center AF point for composition reasons. Here's where back-button AF really helps. The sequence of events goes: center subject in frame, half-press shutter to spot meter (also starts the lens' IS going) and press AE Lock, recompose with selected AF point over subject, press AF-ON to focus, press shutter. All of these were shot using Spot AF:

[Richard Lane]

Neuro, Great Shots and examples of how it should work, when you lock AF correctly. You have wonderful technique and your shots are relatively clear of a foreground mess. I hope that I didn't imply that shots of this nature (pun intended) are unattainable with Spot AF and a confusing foreground and/or background, except for the fact that it makes it more challenging.


Additionally, one user was focusing on a twig which the spot AF is supposed to get around, and the other user was focusing on a birds narrow head in a convoluted, low contrast corn field (not the easiest shooting conditions), so if they're slightly off, then they're OOF.


I believe that the users are not locking AF properly and/or there settings are off, since there are so many confusing choices (quite understandable) and I think that it is a common problem throughout the internet, and one that can be easily rectified with some discussion and practice.


Certainly, we can't be sure at this point if one of the cameras is malfunctioning, however, the OP did mention that he sent his camera to Canon and it checked out fine and he will do further tests on it like HDNitehawk had suggested.


Stay tuned folks!


I will be away from my computer until this evening.


Rich