Horizontal Dark Lines

M

Malko

Active member
What am I doing wrong? I notice that this happens in fluorescent lighting, but my shutter speeds have always been correct... 1/125 for 720/60p and and either 1/60 or 1/125 in 1080/24p, correct? This happens at ISOs all over the map I believe and this particular shot was with the stock lens, though it's just as bad on my 50/1.4 FD.


 
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This is a classic 60 hertz fluorescent lighting sync problem. You didn't mention which shutter you used for this shot, but I'll bet it was 125. The problem is that 125 is not an exact multiple of 60 hertz, so it causes a slow rolling sync problem. Because the GH1 (and most other cameras) don't have any other shutter speeds that are multiples of 60, I think you have to use 60 across the board - for 1080/24p and 720/60p.

As a test, I shot some video under a 60 hertz fluorescent light at many different shutter speeds. I could see the band on the LCD, but it was very subtle at 125. Once I got up to 250 and 320, the video was full of stripes.
 
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That makes sense. So even for 24p, it's better to stay at 1/60 under flou. lights? I don't seem to have that issue with the EX1 I use when I have it set to 1/48 (though I know the GH1 does not do this).

I did have this at 125 because of reading somewhere that it was a good default speed for the 720/60p mode (since it's the closest to 120 as you can get). I just didn't look at the shutter speed as I switched to 1080/24, or else I would have had it on 1/60...
 
Yes, certain types of fluorescents cause the 60 hertz flicker that you see in your video. I think it's only safe to use 1/60 shutter, for all modes, under these lights (NTSC).

Many professionals on this forum prefer 1/50 for 1080/24p, because it approximates the 180 degree shutter of motion picture cameras, and 1/60 for 720/60p, because it's a close as you can get to the 180 degree shutter without forcing the camera to drop frames.

The 1/125 shutter was recommended for slow motion sequences, when shooting 720/60p.
 
I'm paraphrasing what I've read in other posts. My understanding is the following:

1/50 would be the most filmic shutter for 1080. However, 1/60 is better if you're shooting under magnetic-ballast fluorescent, HMI lighting, sodium-vapor or mercury-vapor lighting.

When shooting 1080, it's recommended to stick to 1/60 unless shooting strictly under tungsten or strictly with sunlight, or you know for a fact that the lights use high-frequency electronic ballasts.

Hope I got this right.
 
Maybe I look at the EX1 with less scrutiny - it not being my personal camera, and typically just used for well lit interview shots. On one hand I'm surprised that I haven't then run into this issue earlier in my career but the more I think about it, I almost never shoot anything under florescent. I guess that's a product of only being taught how to do things right (light everything indoors) without seeing the real consequences for myself of not doing it.

Thank you all so much for clearing that up!
 
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