@rob_sheridan asked a question the other day on twitter that i didn't have an answer to:
“Even with a 45mb/s card, I'm still getting occasional stuck frames (1 frame holds for 4) on 5DM2 videos. Anyone know anything about this?”
and someone replied to him and he posted:
“This report of jerky frames when the exposure shifts automatically is consistent with what I've been seeing: is.gd/m8z5 -thx @rikerke”
So, i did some digging only to learn that indeed, there's a known “issue” with the 5D mk ii and video – which as it turns out is even discussed in the user manual (page 124): “If the brightness suddenly changes during movie shooting, that part might look momentarily still”
Ok, so what is this issue? I think the post by sulka explains it well:
“What's happening is, whenever you're recording video, if the camera changes the aperture, it skips 2-3 frames, and replaces those skipped frames in video stream with copies of the last frame recorded.”
It was also discussed pretty well in this DPReview forum thread and this thread with a specific post and an example video where you can plainly see the impact (when the camera switches from the bright outside to the darker interior shot)
Now, there were also posts on twitter about rumors that this will be fixed in the next firmware release, but nobody replied to me asking for documentation of that rumor anywhere. So, we'll have to see when and/if Canon addresses the issue.
Oh, and locking the exposure with the button on the back of the camera or using one of the “aperture control” tricks will prevent the stuck frames in the first place.
Photo Credit: photo by planetMitch