Autofocus when filming with 5D MK III?

Is this the right Forum?

At first: Of course, I do know that the best way is not to use auto-focus when filming, manual focus is prefered because of the better control. and to get rid of the sound of the AF-motor...

BUT, when I do use the autofocus (using the AF-ON button) when filming the whole film gets darker.
Is it some kind of setting / other method etc of using the autofocus so that the film doesnt go dark?
And maybe so that it uses AF all the time instead of just when the button is pressed?

I mean, a cheep Point to Shoot Compact camera can manage this without problems...


/Jocce
(Sorry for my poor English...I'm Swedish )

Check out the new firmware release that supports the 40mm STM lens, I think it's the fix to the darkening in video's, although it may still do the same for non STM lenses on autofocus.

No, that's not the purpose of STM.

The darkening of the frame is because the camera drops the aperture (to increase DOF - gives the camera more stuff in focus/acceptably sharp so that it can properly/more accurately lock focus, due to the way contrast detect AF works).

STM is just a quiet stepper motor to reduce the noise during AF/filming - only really useful for the cameras with continuous af in movies... the 650D/T4i being the only canon dslr to implement it. Don't count on the 5D3 or any serious HDSLRs ever getting that feature, it's just too finicky to ever be useful in serious filming work.

Not really sure theres a way to 'fix' the dark frame 'issue', and after all, AF during filming would look incredibly unprofessional. Just learn to MF like all HDSLR filmmakers do.