I've read that it is possible to have a lamp lit up when your picture is in focus when you are focussing manually. How do I enable this feature on a Canon 5D MkII?
Focus Confirmation is automatic, and should happen on a 5D with all Canon EF lenses.
There are several situations, however, in which the confirmation light may not work. The focus confirmation uses the auto focus (AF) system, so any time that AF is not possible the confirmation light may fail.
Canon has a document that explains these situations in detail but I will list several common ones here.
- AF is not possible due to low contrast.
- An extender/lens combination decreases the maximum aperture past f/5.6, which is beyond the limit for AF.
- The shutter/AE Lock button custom function setting is changed, which can effect AF
I think you have to be activating the AF function (i.e. by half pressing the shutter) as the AF system on a DSLR doesn't do anything until activated.