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Old March 1st, 2007, 06:21 PM   #1
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Issue with fluorescent light and high shutter speed

I am prepping a shoot for a music video where the band will be shot under all fluorescent light. I really don't like shooting under regular commercial tubes but the band insists and there are way too many in the venue to change them out. I went ahead and shot some test footage of the location. Looking at the footage I notice that there is a weird fluctuation with the image and white balance. It seems to get brighter and darker ever few seconds and also the white balance goes from cool to warm during the fluctuation. I am shooting 24p with a 1/250th shutter speed. Has anyone else experienced this? Is this normal for shooting a high shutter speed under these conditions? Any help would be appreciated. Thanks
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Old March 1st, 2007, 08:07 PM   #2
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Using the standard 1//60 shutter speed, or possibley 1/120 should help.

This happens because the line frequency is close to, but not exactly the same as the field rate for NTSC video, and because the output and color balance of a discharge lamp varies somewhat during the line power cycle at the rate of the 2x the line frequency. When you use a high shutter speed, e.g., 1/240, you are reading the light for a small a portion (about 1/4) of the 60 Hz power curve and thus you see the variation. If you use a slower shutter speed the variation is much less because it is averaging the light over the full power cycle. (and it may look even worse if you use a faster shutter) The frequency of the variation corresponds to the difference between the line frequency (60 hz) and the NTSC video field rate of 59.94 Hz).

This is why studio flourescent lamps for video use special high frequency electronic ballasts.
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Old March 1st, 2007, 08:46 PM   #3
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Don is exactly right. You might even be able to dial it in closer by using 'clear scan' as you would with a computer monitor so that you are right on the line frequency.

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Old March 1st, 2007, 10:15 PM   #4
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Thanks alot guys that really clears up alot. I had never had such a request but I guess these guys were inspired by another metal band that did a similar video in real crappy fluorescent light. I will try to do another test using clear scan if not look into some cheap alternative to kinos and just do some CC in post. The only problem is that there are about 30 lights in this square area. Thanks again
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Old March 2nd, 2007, 02:22 AM   #5
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You're shooting at 1/250 at 24p so it's not like you're trying to capture reality. If you want more realism use the synchro/crystal/clear scan and add the effect in post. Also, use shutter speed selectively, it can become tiring and lose it's emphasis fairly quickly. Good Luck.
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Old March 2nd, 2007, 07:29 PM   #6
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Charles,

What effect could I use in post? I have heard that it is impossible to simulate the aesthetic of a fast shutter in post. Also since the band is a hard rock/metal band, the high shutter is suited for the concept and music of the video. I hardly ever get a chance to use a high shutter also so this in fairly new for me.
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Old March 3rd, 2007, 04:14 AM   #7
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You can use the fcp strobe filter with a value between 1.3 and 1.8 to get a fairly decent simulation. It won't emulate it exactly but then again that's the lighting trade-off. I'd just shoot it both ways. Good Luck.
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Old March 3rd, 2007, 02:00 PM   #8
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Shutter effects cannot properly be emulated in post. You can use some smoke and mirrors to get something similar. You dont have a lot of options, the syncro-scan option will get you a consistent image but you lose your shutter options.



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