GL2: color changes during a shot

i just bought my GL2 2 months ago. Lately, i discover a serious problem. when i shot in a not-so-bright environment, the color of some part of the screen (especially the white, sometimes the skin) changes randomly during the shot. it wasn't really obivious. some people can't notice it. (the canon technicians probably) it beomces apparent when u digitlly boost up the brightness on a computer. also, it usually happens when i use a violet tone for my white balancing. I always shoot in manual mode or use one of the preset white balance. It still happens for both modes. I never use auto white balance. I am a film student and have to use the camera for my and other people's work. it really pisses me off. it is a 2000 dollar camera for christ sake. I don't know if it is just my camera or a general problem of the GL2.

anyone experiencing the same problem? also, i bought the GL2 from a authorised dealer in hong kong, but i m now studying in US. what can I do? my warraty say it only covers Hong Kong.

[Ken Tanaka]

(I posted one reply, but immediately deleted it after reading your problem more closely.)

"... it usually happens when i use a violet tone for my white balancing"

Can you tell us more about how your are doing this and the type of lighting you're using?

[Peter Moore]

I have this problem, but ONLY when I use auto-white balance. When I manually white balance I've never seen this happen.

it happened in three different ocassion:

1) room lights (tungsten), manual white balancing with the use of a yellowish orange construction paper as the "white" reference.

2) room lamp (probably tungsten, or whiter light bulbs), with the use of the preset "tungsten" white balance mode.

in both ocassion, things tends to look a bit violet but not very extreme, which looks pretty cool in itself, except for the flickering.

is it possible for me to post some screen capture on this discussion board?

[Ken Tanaka]

No, we have no such graphic posting facility. Email them to me and I'll make them available for all to review here on my .Mac site.

one more thing
in the second situation, i also hv sunlight coming from the window. that's why it is violet

the picture i captured are in BMP and is about 1MB each. I have two pairs of them. is it ok if i email all of them to u?


thanks.

[Ken Tanaka]

Fire away.

to tanaka:

can't seem to reach u by email. hv u get the pictures?

[Ken Tanaka]

I have uploaded Chow Sing Sing's samples to my .Mac site. If you're interested in evaluating them, simply click on the "Chow Sing Sing's GL2 Stills" folder and download the files, labelled "Door.jpg" and "Drawers.jpg".

Note: I have converted them from .bmp to .jpg (minimum compression) to ease downloads for dial-up folks.

[Ken Tanaka]

My opinion: This is a very subtle, nearly imperceptible color shift. I speculate that this was induced somewhere in the color gain system due to extremely low lighting.

To determine if your GL2 has a problem I'd recommend experimenting first with a well-lit, near-white flat subject with a standard white balance. Shoot 10 secs and review for color consistency. Then white balance with whatever you were using for these shots and shoot the same subject again and review. Etc. Make sure you keep gain at 0 throughout your tests.

Basically, determine at what point in the exposure range you begin to observe this shift.

actually that is what i suspect too. when i notice such shiftings, if i turn the gain up , the shifting is gone. I m going to do the test u suggested. i expect canon is better than that. it's very subtle but i still feel bad because the amera is very good i many other aspects.

thank you so much. you have been very helpful to all he DV users around the world.

[Dan Holly]

I have this same issue on my XL1s under florescent lighting when shooting in "TV mode", and using the auto white balance(danger danger will robinson).

On this particular shoot, we had no control over lighting.

Luckily, when this happened we were shooting b-roll footage, so I didn't have to go back and reshoot.

If I get a chance I'll find the footage and post a clip of the issue.
It may be a few days because I'm shooting a 40th b-day party tonight.
(similar deal to how Dylan got roped into the wedding shoot =)

[Ken Tanaka]

Dan,
Indeed, auto white balance is prone to such color shifts and should generally be avoided. But Sing's issue is that this phenomenon occurred after he manually white balanced the camera. That's where the puzzle lies.

[Dan Holly]

Thanks for the clarification Ken, your always a bundle of good info !