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Green tint on outdoor manual WB


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#1 Ollie Bartlett

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Posted 05 July 2007 - 09:41 AM

hey there,

my first post here so a big hello to everyone.

ok here's the deal. whenever i try to manual white balance outdoors, especially in a field or forest, my images always come out with a green tint, forcing me to use the outdoor preset on my XL2.

i cant figure this out as surely it cant be caused by light bouncing off the green surroundings, although i only believe this due to experience white balancing blue to give a warm tint and balancing orange or yellow for a cold bluish tint.

Noobish question i know, and i should know the answer to this problem by now, but its always been too easy to just flip to a preset rather than confronting the problem.

cheers guys,

ollie
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#2 Jason Debus

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Posted 05 July 2007 - 10:23 AM

Are you using a grey card to WB?
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#3 Rupe Whiteman

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Posted 05 July 2007 - 11:28 AM

Yes - the green cast is from the reflected light in the conditions you describe. The foliage/leaves act as reflectors and hence put green into the light they reflect.

... and you should never use a grey card to wb!! Only white card or coloured cards for warming/cooling the wb. You could use a pale green card to take some of the green out if you're manually wb'ing. Otherwise stick to the preset daylight setting.
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#4 Jonathan Bowerbank

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Posted 05 July 2007 - 02:30 PM

Are you using a grey card to WB?


Yeah, wouldn't make sense to use a grey card while WHITE Balancing. Some people shoot a grey card when shooting video though, in case they shoot a scenes at different times and need to balance them in post.

It's most likely the reflection off the green foliage giving you that tint. When white balancing, you can use a giant white card and tilt it just a bit so it catches some of that green. The most effective way would probably be to have the white card in the shade, facing the direction the sun is coming from with the camera turned away in the exact opposite direction of the sun. That way you should get the full green reflection and be able to balance it out.
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#5 Ollie Bartlett

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Posted 05 July 2007 - 06:06 PM

cheers for the reply guys,

im probably totally missing the point, but wouldnt green light reflecting onto the white surface whilst white balancing cause another tone to be prominant?

ie blue filter on white when balancing gives a warm tone afterwards, yellow or orange filter when balancing gives a cool tone afterwards. why would green reflection then cause a green tone? surely it would partially remove the greens from the image as it would recognise those slight greens as actually being white.
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#6 Michael Nash

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Posted 05 July 2007 - 06:14 PM

im probably totally missing the point, but wouldnt green light reflecting onto the white surface whilst white balancing cause another tone to be prominant?


If the white card is in direct sunlight, it's getting far more "white" sunlight than the shadows are. When you white balance to this, light reflecting off the foliage is filling the shadows with green light. If you aim the white card away from the sun, and into the shade where it's catching all that green bounce, white balancing on this will "neutralize" the green bounce. But then, your direct sunlight will look a little pink!

It's always a challenge to get a good manual white balance it mixed light, which is what you've got here. So if your preset is working for you, use it!
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#7 Michael Collier

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Posted 05 July 2007 - 07:29 PM

I think everyone has missed the problem here.

First I have shot a ton outside in all kinds of conditions in foresty locations. Never did the bounce off leaves provide enough level to even put a tint in the shaded areas of frame, let alone in direct sun areas.

Second, and most telling, he is saying he gets the green tint when whitebalancing, but when he switches to preset, there is no tint. If it were bounce off the leaves, it would tint regardless, since the preset would not factor in that green bounce. In fact, if it were bounce, he would find it easier to get proper colors when using a manual balance, and the green tint would be more obvious when using preset.

So I am doubting its bounce off green leaves. As for what it is, I draw a blank. Its really odd for a WB to have a green tint, of all things, especialy if under preset there is none. My gut feeling is that there is a problem with the circut itself that does the whitebalancing. Somehow its seeing more magenta than it should and overcorrecting. Also its possible a setting in the menu only clicks on when its not in preset mode, so a tint might only apply to a WB shot, not a preset (I would say no from my experience with XL2s, but its possible I suppose)

I do have a few followup questions to narrow the possibilities. 1. does the green tint exist only on manual balance outside, or will you get the same effects inside. 2. have you tried whitebalancing under a tungsten light gelled with CTB and got the same result? 3. Have you checked your matrix settings? 4. does the XL2 have a tint control in its setup menu? 5. (most obvious) is your whiteballance sheet actually WHITE?

I would go through those questions, but it sounds like something that a canon repair would have to look at.
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#8 Ollie Bartlett

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Posted 06 July 2007 - 02:42 AM

hey Michael,

in answer to your questions:

1: it only ever happens outdoors (specifically in a field or forrest, city is fine). Indoor WBing has never caused a problem.

2:havnt tried the CTB, or at least not a specific blue with a mind to finding the answer to this problem.

3:colour matrix settings are all fine. i usually only alter them after ive white balanced.

4: i cant remember. it has loads of settings but ill check today after work.

5: white balance sheet is white.

5 more nuggets of info for all you would be digital detectives.
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#9 Michael Nash

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Posted 15 July 2007 - 04:43 PM

I think everyone has missed the problem here.

First I have shot a ton outside in all kinds of conditions in foresty locations. Never did the bounce off leaves provide enough level to even put a tint in the shaded areas of frame, let alone in direct sun areas.


I've had that happen many, many times. In fact it's pretty predictable that green areas in daytime will tint everything up to the midtones green. But each camera has its own biases.

The fact that the manual white balance and the preset look different is almost irrelevant. The preset is just RGB numbers that the camera recalls. Manual white balancing attempts to line up the RGB levels, but is susceptible to the camera's own setup. It's not uncommon for a camera's white balance to come up slightly incorrect, or to not match the preset. I've seen different cameras come up way out of whack, often with different results from different cameras of the same model. After two decades of shooting video I'm actually pleased when a camera is tuned correctly and a manual white balance comes up white, and I can use it reliably. I "paint" or pre-program a white balance whenever possible.

It sounds like this particular camera is just sensitive to green, since the problem only shows up in the presence of green light.
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#10 Chris Keth

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Posted 15 July 2007 - 11:38 PM

I've had that happen many, many times. In fact it's pretty predictable that green areas in daytime will tint everything up to the midtones green. But each camera has its own biases.

The fact that the manual white balance and the preset look different is almost irrelevant. The preset is just RGB numbers that the camera recalls. Manual white balancing attempts to line up the RGB levels, but is susceptible to the camera's own setup. It's not uncommon for a camera's white balance to come up slightly incorrect, or to not match the preset. I've seen different cameras come up way out of whack, often with different results from different cameras of the same model. After two decades of shooting video I'm actually pleased when a camera is tuned correctly and a manual white balance comes up white, and I can use it reliably. I "paint" or pre-program a white balance whenever possible.

It sounds like this particular camera is just sensitive to green, since the problem only shows up in the presence of green light.


Michael sounds right to me but I have one other thing to watch for. Is there a chance the card you white balance with is discolored a bit, say from using it as a bounce too close to a light or something?
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