Have any of you experienced any problems if you use the Zeiss CP2 21 mm as still lens? I know it is a complete manual lens - but I tried to you use it in a timeelapse and experienced that if I tried to you the live monitor as a reference all the pictures where over exposed. But if I tried to set the exposure according to the build in exposure meter - the pictures where fine - but the live monitor shows an almost black and dark picture.
Any ideas why?

I have seen this with Pentax Takumar lenses (with an M42 to EF adapter) as well. It seems to be a bug in the camera that when in Stills mode the screen doesn't accurately reflect expose. However, if you switch to Movie mode the exposure will be reflected properly on the LCD screen.

I did a timelapse with a Zeiss 28 recently and never had that problem. But like Jeremy said I set my exposure in movie mode, I never thought about the still mode thing. I used Aperture priority mode and make use to use the eye piece cover on the back.