strobing red vest

ramkuma

ramkuma

Well-known member
My co-worker shot an interview indoors with someone wearing a bright red vest which glows in and out. Both white balance and iris were on auto setting. Was it the auto white balance that caused this?
 
No, fluorescents can flicker (as can many other ballasted lights); your eye doesn't see it, but even some modern electronic ballasts will flicker at a high enough shutter speed.

Thing is, you don't see it as a "flickering" - more like a steady pulsing of brightness levels, depending how your shutter synchs with the frequency of the ballast. Take a camera to a lighting store and watch the LCD at anywhere from 250th - 1000th shutter, pan around the different lights - you'll see the effect.

In the US, shooting at 1/60th can alleviate much of this since we're on 60hz power.
 
On a CCD camera, shooting with a high shutter speed under fluorescents can cause a constant cycling color shift, it almost looks like continuously-hunting automatic white balance.
 
Barry_Green said:
On a CCD camera, shooting with a high shutter speed under fluorescents can cause a constant cycling color shift, it almost looks like continuously-hunting automatic white balance.
Click to expand...


Interesting. It was shot at 1/60 at 30fps. Doesn't seem that 1/60 would be fast enough to do the hunting automatic white balance (this is exactly the effect that occured)? Next time when shooting under flourescent should I go down to 1/24?

On the flip side, perhaps it was the fact that the camera was in auto white balance that caused the strobing/hunting on the red vest.
 
No, you should stick with 1/60th. If you were on 1/60th, then that didn't cause the issue.

But if you were in AWB, that could have caused it.
 
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