Can I get some body focusing info on low aperatures?

I know we see a lot of lenses mounted where there's problems with front/back focus or other issues at aperatures of f/1.4-f/2.8

Isn't there some spec where 300/350d's only will focus down to a certain F range? And then the spec is F lower for bodies like 20/30d's?

I want to rattle off some numbers, but I just went through the 350d and the 20d manual and didn't find anything. I do know that the AF center on the 20d is better than the 350d. Something about | vs +. Can we get some clarification on this?

I think what you are refering to is more of a dof issue, rather than a focusing problem. At those large apertures, depth of field can be so narrow that it appears that there is a focusing problem.

This might help:

http://dofmaster.com/a​rticles.html

http://www.dofmaster.c​om/dofjs.html

Nope talking about the autofocus on fast lenses.

My equipment works great. I just see references to fast glass that bodies can't handle every now and then.

Maybe it's an urban rumor.

I don't know about fast lenses that a body can't handle. However, certain camera bodies have AF sensors that behave differently with faster lenses. Specifically, the center AF point on many camera bodies will function as a cross-type (both vertically and horizontally) sensor when f/2.8 or faster glass is mounted.

A 1 series body will autofocus with a f8 lens (center point only) Most of the other bodies need f5.6.

While we're on the 1-series, it features 7 cross-type AF sensors when f/2.8 or faster glass is mounted and a cross-type center point AF sensor with f/4 or faster.