Streaking caused by flash

J

jeremycloe

New member
I recently shot a wedding on the 7d and there were three photographers shooting photos while i was shooting video. Every time one of their flashes went off it distorted my image with huge ugly horizontal lines. It was almost like interlaced footage blowing out. I haven't had too much experience with digital slr's shooting video. Any idea how to avoid this in the future? Thanks for your help!
 
Welcome to the world of rolling shutter CMOS cameras.

Look at this article for a discussion on what happened to you (the "partial exposure" effect).

And no, there's not a thing you can do about it. You can try to fix it in post by blending a white frame onto the unflashed portions, but you can't do anything to prevent it from happening in the first place.
 
If you're talking about split frames - where the flash image only shows up in part of the frame - it's the nature of the rolling shutter in CMOS cameras. The flash is occurrring faster than the camera scans the sensor, so the flash frame only appears on part of the frame. There isn't much you can do if there are flashes going off while you're shooting.

Here's an example shot with an EX1 (another CMOS camera)
http://freshdv.dreamhosters.com/mjeppsen/video/ex1_strobe_cmos_rolling_shutter_artifact.mov

If that's not what you're seeing - then post some grabs so people can hopefully help you figure it out.


EDITED TO ADD:
Typing while Barry posted I guess.
:)
 
It is what it is. Not much you can do about it.

But keep this in mind… In "The Informant" there's a shot where a photographer shoots a flash, and there's one frame of partial exposure on screen, just like in your footage, probably. Of course I think I was the only person in the sold out theater who noticed, including the wookie sitting next to me. :D
 
stephenmick said:
But keep this in mind… In "The Informant" there's a shot where a photographer shoots a flash, and there's one frame of partial exposure on screen, just like in your footage, probably. Of course I think I was the only person in the sold out theater who noticed, including the wookie sitting next to me. :D
Click to expand...

Seriously?
I totally didn't notice it at all....
hm

I guess I'll take your word for it.
:)
 
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