Is this an example of rolling shutter phenonemon?
 

One of our videographers shot this today with a 5D Mark II. I've never seen camera flashes come out this way on any of his other videos.

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Yep, that's exactly what that is. The duration of the other camera's flash is shorter than a single video frame, creating "flashing banding" in a few consecutive frames (due to most cameras having a pre-flash for focus assistance). You'll get it with strobes at parties, too. It's caused from the pixels of the CMOS sensor being scanned from top to bottom one line at a time, rather than simultaneously like a CCD sensor. The effect it has on a CCD sensor is different brightnesses from frame to frame instead of banding, due to the timing of the flash. If a flash goes off at the beginning of a given frame, that frame would be brighter than the one following it where the flash only lasted for a fraction of the duration of the video frame. There's a trade-off though. CCD sensors will give light-streaks (think flashlights, candles, christmas lights, light bulbs, etc) which appear as either vertical or horizontal, edge-to-edge streaks that emit from light sources.

An easy way to deal with this in post is to just use a white flash for the whole frame. Strobe lights firing quickly are probably something not ideal for a CMOS camera, but that is a rare occasion.

BTW, its "phenomenon".

Good evening,

If you shoot many weddings, you better get the software that cleans that up for you!! I believe its new blu. It will save a lot of time. I shoot two cameras and i just swap cameras when that happens. as my second camera is a ccd camera.

dale

PHENOMENON

You are correct, Marcus. I can spell, I just can't type...:)