5D mk 3 2 quick questions

[Totti]

On mobile phone so will keep this brief as I can't find in manual:
1. Why does focusing sometimes flash AF point (av) sometimes not?

2. What is the process begins focus recomposing? Half press shutter on point, then keep half pressed while I frame and then click? Also what would be the point? If subject moves or if you want to use stronger AF points is my only guess.

Many thanks

Stef

[neuroanatomist]

If you mean flash red, it does that when focus is achieved and the light levels are low (there's a setting that controls that - AF point illumination can be off, on, or auto - yours is set to auto).

Yes, if you want to focus-recompose, you half-press the shutter with the selected AF point on the subject, then recompose, then shoot.  It's a bad idea from the center point with fast primes shot wide open, because it results in backfocus.  You may still need to even with the 5DIII, if you want the subject outside of the AF point spread, but start with a point at the edge, not the center.

[Dylan777]

With 61 AF points, do you really need re-comp?

[spinworkxroy]

With 61 AF points, do you really need re-comp?

Actually yes sometimes,  because i personally only use spot focusing so either i manually move the focus point, or i'll recompose..

[neuroanatomist]

With 61 AF points, do you really need re-comp?

Yes, if the subject is outside the AF point spread...

[Totti]

With 61 AF points, do you really need re-comp?

Actually yes sometimes,  because i personally only use spot focusing so either i manually move the focus point, or i'll recompose..

Thanks for the responses guys. apologies but it's all new to me. I've got a 5D and 2 lenses: 50 1.2, and a 24-105.

When you say you only use spot focusing, is that just the one little dot for focus? I have been using the one with the adjacent points unless I really want absolutely precise focusing..

It's been great delving into the world of semi manual photography. I've never had to specify AF points before (Sony a350 just used to leave it on auto) so while it's been a challenge thinking about where to focus every time i shoot, it's such a joy when you get it right.. Especially on 1.2 =)

[Mt Spokane Photography]

With 61 AF points, do you really need re-comp?

Actually yes sometimes,  because i personally only use spot focusing so either i manually move the focus point, or i'll recompose..

Do not use recompose with a fast prime like the 50mm f/1.2, at least not, unless you are at f5.6 or less.
 
The depth of field is very shallow at wide apertures, and you will be out of focus most of the time.  If you must use recompose, sell the 1.2 and get a cheap small aperture lens that will give you more depth of field.
Thanks for the responses guys. apologies but it's all new to me. I've got a 5D and 2 lenses: 50 1.2, and a 24-105.

When you say you only use spot focusing, is that just the one little dot for focus? I have been using the one with the adjacent points unless I really want absolutely precise focusing..

It's been great delving into the world of semi manual photography. I've never had to specify AF points before (Sony a350 just used to leave it on auto) so while it's been a challenge thinking about where to focus every time i shoot, it's such a joy when you get it right.. Especially on 1.2 =)