As I have tested a lot of times when I am using my Mark III with a 580EX flash having enabled in custom functions of MarkIII the use of AF-Assistbeam it always makes OOF shots. I use the central AF point. Has anybody any idea about that issue?
Canon EOS 1D MarkIII white paper mentions that this function is supported on 580EX II and 430EX and it does not mention 580ΕΧ.
I can see the assist beam fire but in most cases the by utilitising as assist to one shot AF I see OOF shoots. On the other hand if I deactivate that option from the custom functions of MarkIII (disable speedlight assist beam) then it focus just perfect. Thats why I am trying ot find out what is going on.
I always use the flash in upside position for flash thru the ceiling
Ok you can control the AF assist beam in camera with the 580ex 1 or 2, did not know that but just gave it a whirl to be sure.
I'd be curious for you to test the assist beam by turning it on only in a dark room with a solid colored wall where the camera can not focus without it. What happens then?
In any case you should obviosly get in focus shots either way. Post examples, what shutter speed and aperture are you at? How far is the test subject from the camera and what lens? Have you tried other lenses?
Well Everything is OK I just tested again and it seems that finally it nothing wrong it works fine with AF beam assist enabled and the best way to work is in Manual mode for EOS 1D
