[1200D] Video under-exposed for a few frames

[Telemak]

Hi!
I have install ML on my 1200D and i have a little problem (sorry for the english)
I have, randomly (or not) some frame under-exposed, after 1 second the exposition back to normal :O
A video of my problem:https://drive.google.com/file/d/0B1YOcN703yUCNFpLLS1SWjRnMHM/view
Thanks for your help!
Théo

[Levas]

Probably some autoexposure settings at work there.

For filming without autoexposure, you must be in M-mode on the mode dial and set shuttertime, aperture and ISO values yourself.
This was probably filmed in Tv,Av or some other mode.

[Walter Schulz]

Or 50/60 Hz flicker:
http://urbanvideo.ca/avoid-video-flicker

[Telemak]

Thanks for your reply!
My EOS 1200D have a "simple" video mode, i can just set ISOn (other parameters are set by the Canon firmware) with ML i can bypass this problem
Without ML, i can only set "manual exposure" on Canon setting, when "manual exposure" is enable on the Canon firmware, the button to open ML (the bin) dosen't work, when manual exposure is disable i can access again to ML
And i have do some test, is not a frequency problem :/
Thanks!
Théo

[a1ex]

Some lenses are known to do this when you use exposure override on other cameras, but no idea how to fix. Does it help if you unscrew the lens a bit after setting the aperture?

[Telemak]

I try this, i don't very know if that resolve the problem
How can i holding the unscrewed lens?
Théo