How to deal with stroboscope effect caused by room lights at DVinfo.net

David Niemeijer · May 23rd, 2007, 04:14 AM

I recently shot some HD footage in a school using a PAL 1080i camera from Sony. Later, when editing the footage I noticed there was a slight stroboscopic effect on the material (a bit like what you see when shooting a CRT monitor or TV with a DV camera, but less pronounced). My guess is that it was caused by a difference between my capture frequency and some native frequency of the lights in the room. Is there any way in Final Cut Pro to correct for this. Is there a way to prvent the issue from ahppening while shooting, for example by adjusting shutter speeds or so?

Thanks,

david.

Dean Sensui · May 24th, 2007, 02:01 AM

If your camera has a "clear screen" feature, which is actually intended to allow the camera to sync with the flicker of computer CRT's, then that would solve the problem.

I ran into the same issue in New Zealand, using NTSC cameras under 50 Hz fluorescents.

The gelled tungsten lights we used helped mask the problem -- which went unnoticed until it was too late. That's one of the follies of rushing a setup.

By the way, there's a difference between working quickly and rushing. Rushing often leads to carelessness and mistakes.

Marcus Marchesseault · May 24th, 2007, 06:24 AM

Changing shutter speed can help, but it is not very likely to work. I have a method that works, but it won't work with most cameras. I can set the V1 to 1/30 shutter and shoot 30P so I still get the full framerate, but the motion blur is excessive for most purposes. No fluorescent light flickers as slow as 30 times a second, so 1/30 shutter will always work, but that's a really slow shutter and I would only use it in extreme circumstances.

May 23rd, 2007, 04:14 AM	#1
David Niemeijer Tourist Join Date: May 2007 Location: Amsterdam, Netherlands Posts: 4	How to deal with stroboscope effect caused by room lights I recently shot some HD footage in a school using a PAL 1080i camera from Sony. Later, when editing the footage I noticed there was a slight stroboscopic effect on the material (a bit like what you see when shooting a CRT monitor or TV with a DV camera, but less pronounced). My guess is that it was caused by a difference between my capture frequency and some native frequency of the lights in the room. Is there any way in Final Cut Pro to correct for this. Is there a way to prvent the issue from ahppening while shooting, for example by adjusting shutter speeds or so? Thanks, david.

May 24th, 2007, 02:01 AM	#2
Dean Sensui Inner Circle Join Date: Oct 2001 Location: Honolulu, HI Posts: 2,054	If your camera has a "clear screen" feature, which is actually intended to allow the camera to sync with the flicker of computer CRT's, then that would solve the problem. I ran into the same issue in New Zealand, using NTSC cameras under 50 Hz fluorescents. The gelled tungsten lights we used helped mask the problem -- which went unnoticed until it was too late. That's one of the follies of rushing a setup. By the way, there's a difference between working quickly and rushing. Rushing often leads to carelessness and mistakes. __________________ Dean Sensui Exec Producer, Hawaii Goes Fishing

May 24th, 2007, 06:24 AM	#3
Marcus Marchesseault Trustee Join Date: Nov 2005 Location: Honolulu, HI Posts: 1,961	Changing shutter speed can help, but it is not very likely to work. I have a method that works, but it won't work with most cameras. I can set the V1 to 1/30 shutter and shoot 30P so I still get the full framerate, but the motion blur is excessive for most purposes. No fluorescent light flickers as slow as 30 times a second, so 1/30 shutter will always work, but that's a really slow shutter and I would only use it in extreme circumstances.