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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old May 4th, 2003, 01:34 PM   #1
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Drifting White Balance

Every so often folks have reported slowly drifting white balance (slow shift back and forth between blue and orange over several seconds).

I've observed this to happen with flourescent lighting and a fast shutter speed setting. It is a probably beat between the 120 Hz lamp arc frequency and the NTSC field rate.

If I use incandescent lights or normal 1/60 sec or 1/120 sec shutter the problem goes away.

Probably not applicable to PAL systems, and probably not an issue with high frequency flourescent lighting systems.
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Old May 4th, 2003, 02:29 PM   #2
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Hey Don,

thank you very much for your report as I thougth that there's something wrong with my XM-2 (PAL of GL-2). So, this effect is not limited to NTSC. I was shooting with high manual shutter speed, manual white balance, manual focus and got that slow shift back and forth between blue and orange, too. We were using normal flourescent lighting, not high frequency so I cannot tell you if this eliminates this issue.

But I would love to hear from someone who has similar problems or solutions because this is really annoying.

Chris
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Old May 4th, 2003, 04:01 PM   #3
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Avoid short shutter settings when mains fed fluorescents are around.
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Old May 5th, 2003, 04:51 AM   #4
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Interesting to hear that it is an issue with PAL as well. Thanks for the additional feedback.
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Old May 5th, 2003, 09:41 AM   #5
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I had this happen on a shoot a couple of months ago with my GL1. I was using the auto WB since I was filming a continuous shot from outdoors to indoors. The WB was fine outside, and it adjusted correctly once inside, but after a minute or so, it started to drift. The indoor lighting was incandescent. After switching to manual, everything was fine, but I had to split up the shot into two takes.

Rick
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Old May 5th, 2003, 01:37 PM   #6
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In auto mode the WB is adaptive with some time delay. This could well have been yr case. It's excluded that WB gets a periodic drift with incandescent-only lighting.
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Old May 5th, 2003, 06:00 PM   #7
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IMO

Avoid auto WB at all costs under flourescent lighting.

The same thing happens on my XL1s under the same conditions you describe. It's not exclusive to the GL1 or GL2.

Pick up some WB cards to match your needs, and the problem will most likely go away.

******edit, my bad on the manual versus auto*******
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Old May 6th, 2003, 02:02 AM   #8
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Dan,

I thought that using WB cards is called "manual white balancing".


Chris
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Old May 6th, 2003, 04:36 AM   #9
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The whole problem exists because of the (slight) frequency difference between mains power and the camera framerate. Manual WB doesn't solve this problem. If you are lucky and there is very little (less than 1/20 Hz) freq difference and a TTL and not to slow reacting auto WB, the Auto WB can correct the problem by compensating the (slowly) continiously changing WB. And again set 1/60 or 1/50 shutter time under fluorescent conditions in order to minimize the effect
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Old May 29th, 2003, 04:29 AM   #10
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WB shifting

I've been using an XL1-s (PAL) in a studio with a white backdrop. For lights I've just been using 500W halogens.

Whilst it's been possible to achieve the correct colour balance, I've noticed a slow shift from white to yellow on playback. This occurs over around 5 seconds. The shutter speed was around 120th, but next time I will try changing it incrementally to see the effect. Thankfully it wasn't too difficult to remove the subject and place them on a white background when editing, and the shift was slight enough that you don't see it on them (just the original white background).
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