back focus issues

I am doing some more tests with my BMCC and am noticing I am appear to have back focus issues with my Canon 16-35mm f/2.8 L and my Canon 24-70mm f/2.8 L. Has anyone else had this problem? They work fine on my C300. I understood that the mount was designed to avoid such issues.

Any ideas?

Do you mean you can´t reach infinity or that your lenses are not parfocal?

What I mean is that if I zoom in to an object say 2ft away, focus, and then zoom out to my desired shot size the focus doesn't hold and the picture is soft. I the have a to tweak the focus to make it sharp again. Have tried all my L series Canon zooms and have the same problem.

In answer to your question my lenses should be parfocal but aren't performing as they should on this camera.

Same here...

Hi Christian I have spoken to Blackmagic here in the UK and they're going to check it out for me let me know. I will let you know what they say.

Your lenses are not parfocal. That is the problem. Same problem in my 5d and same lenses.

It's one of the problems of still zoom lenses. Most I find don't hold a sharp focus while zooming.