Rolling Color Bars on Image??

T

tommygdawg

Well-known member
Hey all,


I've recently noticed this on my GH1 footage. I was scrubbing through it and saw a strange banding-type effect. It's not the same as the FPN or banding we (or maybe just I) have seen before. It's like colored bars, tinted green (perhaps the color changes), that rolls up the image in every video I record. I notice it most in underexposed/lowlight areas with mainly flat-colored surfaces.

I'm not sure what this is. But it's just colored bars that roll up the image. It's not a huge deal, in fact it's hardly noticeable. But lately it's been getting me really curios. Any thoughts?




Thanks!
 
It's caused by shooting at a shutter speed other than 1/60th. It happens on all CMOS camcorders. If your power system is 60Hz (USA) and you shoot at 1/60th, you'll never see this. But if you shoot under fluorescent or HMI lights and you use a shutter speed other than 1/60th, this can happen.

So don't ever shoot at any shutter other than 1/60th unless you know exactly what you're doing.
 
Interesting! Does this only happen when near electronic light sources (i.e. not the sun, candles, etc.)? For instance if I was shooting outside at 1/50th, would it happen?
 
It's safe to shoot in sunlight at 1/50th. You can shoot under Tungsten/incandescent light sources at 1/50th, but to stay safe, it's a good idea to shoot at 1/60th (in the U.S.)
The problem is with lights that use non-continuous power, like fluorescents and HMI's.
 
Magnetic-ballast HMIs, magnetic-ballast fluorescents, and street lights and stadium lights (mercury & sodium vapor) all cause it.

Sunlight and tungsten light, as well as high-frequency electronic-ballast HMI/fluo lights, should all be immune from it.
 
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