Canon Iris Pump when One-shot autofocusing

[stu aull]

When I do a 1/2 depression of "record" button to set focus (one-touch-auto), the iris opens noticeably for a sec then resets once focus locks.
Is this a situation others are having?
New to the whole auto-focus thang on Pro cameras. But my home DV camera does this pretty seamlessly...
Kind of shoots a hole in the follow-with-auto-focus dreams I had while rolling a take... or I have a problem?

-Tokina 11-16 Canon
-28-135 Canon

Stu Aull
S-X #199
Alaska

 

[Trevor Meeks]

I think it has to do with the lens letting in more light to assist focus, but I could be mistaken.

Also, i wouldn't ever expect to have smooth following auto-focus with a still-camera lens. Just sayin'

 

[Thomas Kruesselmann]

autofocus/touch focus does not work at all for me. pumping like hell. manual with confirmation is best. (scarlet-x, ef-s 17-55 2,8)

 

[stu aull]

thanks.
Maybe less of an issue outside with lots of light (??). Was diddling with this is a pretty poorly lit room, so makes sense to crack open the iris to max to assist. Clever actually...

Stu Aull
S-X #00199
Alaska

 

[Jack Shanahan]

i think its switching between RAW view and the other view. if u notice the color changes too....

 

[Tehben Dean]

FWIW DSLR's always focus wide open (dunno about in live view etc) I'm assuming because its more accurate and faster. It appears like Jack said that EPIC is just switching to RAW view or something to focus and it doesn't do that while recording so don't see it as a problem.