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Old January 6th, 2008, 09:32 PM   #1
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Another newbie question about white balancing.

First, let me thank everybody on this forum who continue to answer my questions even though at this point i don't have enough experience to answer others', you've been a big help! Suppose your shooting under an orange lamp and you want to accurately depict the orangish cast of the light. If you white balance under the lamp the camera will "correct" for the orangish tinge and shift it more towards the blue spectrum right?

1) So, in the absence of some kind of color temp meter, would you just have to eyeball and roll the temp back down? Would there be any point to WB in the first place in this situation?

2) In theory, wouldn't white balancing shots at a bunch of different locations that have different lighting situations "neutralize" all of the color temps giving all the shots an overall consitency at the expense of fidelity to the original appearance of the sources?

Last edited by Cal Bickford; January 6th, 2008 at 10:31 PM.
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Old January 7th, 2008, 12:56 AM   #2
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The answer to number 2 is an overwhelming "yes." This is why I use white balance presets more often than not. I mean, if I'm in a room with nice warm tungstens light, why would I want to neutralize that warmth? If I did, I would use a white card to balance, but I rarely want that. I like the variety of light color we find everywhere.

Typically, the orange light we sometimes encounter out and about, is sodium vapor or something like that. If we go by what we know about visible colors and their respective color temperature, we know that orange light has a low color temp (<2700K). If you balance with the tungsten preset, you should get somewhat accurate, orangish color, though it may appear reddish in some cases. I've had mixed experiences. If it's not quite how you'd like it (and you're viewing a color-accurate source) tweak. Definitely start from the tungsten preset, though. White balancing to that source will just neutralize the orange effect and you seem like you don't want that.

Good luck.

~~Dave
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Old January 7th, 2008, 12:52 PM   #3
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What kind of camera are you using? Professional shoulder mount camcorders usually white balance exactly neutral no matter what light there is. My experience with consumer camcorders is that they won't white balance like that, they white balance in steps, I guess to prevent neutralizing every color in full auto w/b mode (what most people will use with these camcorders).
Even semi-professional camcorders like the DVX100 don't seem to w/b as accurately as a professional camcorder. For example I can't see much of a difference when I white balance a DVX100 through a 1/4 CTB and without a filter. With a shoulder mount like the Sony DXC D30/35/50 there is a distinct difference, the picture is extremely neutral without the filter and, when using the 1/4 CTB, looks about the same as the DVX's picture without any filter. That means the DVX's white balance is warmer by default.

If you want to keep an orange/yellowish color tone with a shoulder mount camcorder, first white balance to the source and see what you get. If it says "2700K" then you will get a really nice yellowish warm color with the 3200K preset. If it says "2200K" then you should start to worry that the yellow tone might become a nasty orange/red. So if you get 2200 but still want to keep the yellow tone then there's two possibilities: either use a light CTB filter (1/4 is good in my opinion) in front of the lens (respectively a 1/8 directly on your white card) or find a light source with a higher temp (your on-camera light for example) and mix the light sources until you get a white balance a few hundred Kelvin higher than 2200 (like 2700 in that case)

If your camera has a color display, then you roughly see what you get. I say roughly because the displays are never accurate, you need to practice a little with the looks of the display and the corresponding picture on an accurate monitor.

Quote:
2) In theory, wouldn't white balancing shots at a bunch of different locations that have different lighting situations "neutralize" all of the color temps giving all the shots an overall consitency at the expense of fidelity to the original appearance of the sources?
That is very true indeed, but unfortunately not everyone who claims to be a professional has thought about it. There's too many people who white balance whenever they move their tripod a few feet from the original position.
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Old January 8th, 2008, 07:47 AM   #4
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Heiko- I'm using an A1.

So I guess the only way to try and maintain color fidelity is to eyeball it huh? I've been using an 18% grey card to WB but maybe a white card would work better for eyeballing K temp.

Also, I saw it asked somewhere else here but didn't see an answer - I understand why an 18% grey works for WB (as well as a black card). In theory, should any card w/ equal RGB values work? ie: 20/20/20, 7/7/7, etc...
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Old January 8th, 2008, 10:20 AM   #5
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For the record, I don't believe using an 18% Grey card is an accurate thing to white balance with. Grey cards are for exposure. For white balancing, if you want to get a neutral white balance (this doesn't apply to your orange light question), you should use a white card (or wall or sheet of paper) that is being hit by the light you want to show up as white.

When you tweak, like Heiko and I said, make sure you're looking at something that is calibrated and accurate. Camera LCDs aren't always reliable, so test and test again.

Also, when you're tweaking, I suggest looking at a frame you're going to shoot rather than the white card, just so you can see how each adjustment affects your whole image.

Good luck.

~~Dave
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Old January 8th, 2008, 12:22 PM   #6
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Quote:
o I guess the only way to try and maintain color fidelity is to eyeball it huh?
100% color fidelity is hard to achieve, because the human brain white balances as well. A halogen lamp in a daylight environment looks yellow to the eye while in a low-Kelvin tungsten environment it looks bright white. However if you take your camera and white balance in daylight, then the halogen lamp looks more orange/red to the camera than to your eyes in the same situation. If you compensate for that with another white balance then the daylight will become blue, which isn't the case for your eyes...
If you look at a window from inside a tungsten lit room, the window will never appear as blue and the room never as orange to your eyes as they will to the camera. The only way to represent the "real" look is to light the room with 3200K and bring the window down with something like a 3/4 CTO

The presets on a camera (tungsten and daylight) are supposed to represent the best color fidelity possible in typical situations. They fail however as soon as something like a greenish fluorescent is involved (that's why some camcorders/photo cameras do have a fluo preset as well). They also fail when the color difference becomes too big (like the 8000K window and the 3000K room in the same frame)
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Old January 8th, 2008, 06:19 PM   #7
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For those

Hi all:

For those of you who are new to the game, if you use FCP, you will find shooting with a Kodak stepped gray card is a great idea. The card has black on one end, and white on the other with all of the steps of gray in between. If you shoot the card under your lighting sources for every setup, you can get a really nice starting place for white balance with FCP's three way color corrector by simply using the three eyedroppers, one each on black, gray and white which correspond to your darks, midtones and lights.

Many new users are intimidated by the three way color corrector but this method makes it really easy to get into using it. Then you can begin from an accurate point and tweak it from there to your taste. As a lighting cameraman, I like to shoot as close to what I want the end product to look like as possible but I have found that when you are shooting low color space formats like DV, HDV, XDCAM EX, etc. it is wiser to get a neutral signal onto the tape/card, then CC to get the color you want in post. If you are shooting a 4:2:2 format like DVCProHD, etc. You have a bit more latitude to play.

Hope that this helps!

Dan
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Old January 11th, 2008, 08:49 AM   #8
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thanks, its much clearer now!
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