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Old November 8th, 2002, 03:31 PM   #1
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White or Gray Card for White Balance?

Either one better?
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Old November 8th, 2002, 04:52 PM   #2
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I bought an 18% grey card. Perhaps I did it wrong, but I didn't like the look at all. They say white, however, can saturate the luminance in the camera.

Someone on here (I'd credit them but I don't know who it was) had this tip for creating "warm balance cards" that give a warmer look to footage. If you don't have these programs, you can always go to the local Kinko's and get it done.



"To make the cards I used CorelDraw and printed in "best quality" on 8 1/2 X 11 card stock, but
Photoshop should do the trick, too. The color saturation values (C-Cyan, M-Magenta, Y-Yellow, K-Black)in percentages I used were:

Warm 1 -- C/15 M/2 K/5
Warm 2 -- C/20 M10 K10
1/2 Warm: C/7 M/1 K/2
Minus Green: C/10 Y/10 K/2
1/2 Minus Green: C/5 Y/5 K/1"
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Old November 9th, 2002, 08:39 AM   #3
 
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Be aware that the white balance setting on any DV camera is very sensitive to color in the reference card. This includes the effect of the light being used to illuminate your "white card" during calibration. For example, if you white balance early or late in the day, under sunlight, the yellow tint of the light during that time of the day will affect the overall white balance as somewhat blue and cold. I've found the best white balance lighting to use is noontime on an overcast day, with diffuse light...no shadows....and use that 18% gray.

Good luck.
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Old November 9th, 2002, 08:50 AM   #4
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Well, I have been using a gray card and it seems to work well. I wanted to see what the group was using, plus I think this is an excellent topic for newbie shooters.

BTW, is there some place to get those white balance cards that are different colors? I know that some shooters like them because it can enhance certain colors during production.

Thanks
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Old November 9th, 2002, 12:10 PM   #5
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I don't understand why anyone would use a grey card for white balance. The grey card is for exposure, pure and simple. I can see using a colour for effects but grey?

Which is better for white balance, I'd say white. I have a 3x3 swatch book for creative WB, the most used gels are 1/4 to 1/2 CTB, Straw and CTO
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Old November 9th, 2002, 01:12 PM   #6
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As long as there is enough light, white balancing will work with 18% reflectance cards too. White balancing is a matter of ratio's between RGB (mainly RB) ratio's in a scene, not the absolute light levels.
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Old November 9th, 2002, 01:44 PM   #7
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I picked up a set of white balance cards from warmcards.com

They have a white balance card system that is very portable and comes in different gradations depending on what the available lighting is like.
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Old November 9th, 2002, 02:01 PM   #8
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"Be aware that the white balance setting on any DV camera is very sensitive to color in the reference card. This includes the effect of the light being used to illuminate your "white card" during calibration. For example, if you white balance early or late in the day, under sunlight, the yellow tint of the light during that time of the day will affect the overall white balance as somewhat blue and cold. I've found the best white balance lighting to use is noontime on an overcast day, with diffuse light...no shadows....and use that 18% gray.
"

In general, I have found that white balancing in the shadows rather than in direct sunlight gives the most pleasing results...warmer skin tones and neutral shadows. When the late afternoon sun becomes noticeably warmer, this will preserve that look rather than neutralize it. It's important to keep white balancing through this period before the sun goes down to maintain some consistency.

I have always used a white card, just make sure that you expose for it which may be different than the scene you are shooting. I don't see why a grey card will work also, but if you are moving fast and packing light, there's plenty of white objects around (paper, clean t-shirt) but the card is one extra thing to haul.
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Old November 9th, 2002, 06:02 PM   #9
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So Charles if I understand you right there really is no difference in using a gray card vs. a white card? [b]HOWEVER[B], since most scene likely have white objects than gray ones to white balance the cam on, white is probably a better choice?

I guess the question now would be is how important is it for the white balance target to be really, really white? Could you mix gray card and white cards without much (or noticable) difference?
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Old November 9th, 2002, 10:48 PM   #10
 
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An 18%gray card is smack dab in the middle of the luma range of black to white. 18% grey, while reflecting only 18% of the light striking it, is, nevertheless 50% black and 50% white. The advantage to using this to calibrate a still camera lightmeter is obvious. Movie cameras are a little different because of the issues of white balance. The camera lightmeter can't tell the difference when it comes to white, between 7.5, 18, 50, 70, 90 or 100 %. I contend that a white card, if the illumination is too bright, will saturate your light meter and hose up the white balance. An 18% grey card is less likely to do this and since white balance only measures luma, the camera doesn't give a rat's axx whether it's 18% or 100%.

I suggest you check out this website: http://www.geocities.com/hollywood/l...2/expose01.htm

It's got some extremely interesting and useful info about white balancing.
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Old November 10th, 2002, 04:59 AM   #11
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An interesting site, Bill. Two remarks however:
- On yr post: whitebalancing is based on RGB ratio's measurements and not on luma. Saturated luma outputs (about)equal amounts of RGB and like you mention BW corrections aren't possible anymore.
On the article: an incident lightmeter doesn't measure 18%, it just caculates out of the 100% incident light, what the exposure setting need tol be at 18% scene content.
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Old November 10th, 2002, 07:17 AM   #12
 
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DRE...

Yep....I learned the Zone Sytem on 35mm still photography. It has a use in video, IMHO. Indeed, if I go into photoshop and set up three "cards" at:
1-16, 16, 16
2-120, 120, 120
3-255,255,255
I will get three cards at 7.5 IRE, 50IRE and 100IRE

RGB indeed maps to IRE. Note that most image editting programs will map an RGB of 16x16x16 to the setup value.
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Old January 10th, 2003, 05:25 PM   #13
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white balance

you can use almost anything to white balance off of as long as the color components are identical to pure white. one trick that I learned years ago...rather than spending money on "warm cards"...get free "Jungle swatch book" from Roscoe or Lee...they are big (about 3" square) swatches of gel, including all of the Blue Correction and CTO orange gels....just pic the amount of warm or cold you want to add or detract, stick the swatch in front of the lens when you white balance, and tweak as needed.....great if you are in a pinch....the ORTHODOX way to adjust color is to white balance, then add correction with gel over the fixtures..the swatch book is the quick and dirty way too do it.
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Old January 11th, 2003, 05:47 AM   #14
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Steve:

I've never used the warm cards, but I can see a certain advantage in that it can be physically awkward to wield the swatchbook in front of the lens, particularly when shooting handheld. Imagine that late afternoon run-and-gun mode, having to fish the Jungle book out of a pocket and select the gels, all with camera on the shoulder.

And incidentally, great minds do think alike (or in my case, substitute "fair to middlin'" for "great"):

http://www.dvinfo.net/conf/showthrea...ht=jungle+book
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Old January 11th, 2003, 01:38 PM   #15
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Just remember that it is not always desireable to white balance. For instance, if you white balance in the late afternoon light, you eliminate the lovely warm color that is available at that time of day.

Additionally, if you "cheat" the white balance using warm cards or balancing through a blue gel, you are making global corrections to your picture. That means that the blue suit the executive is wearing will become brown. Not a good thing.

The best time to improve the look of the picture is in post, where you have more control over the corrections. This is one of the reasons every foot of film that is shot goes through color timing.

Remember that all whites are not created equal. There will be subtle color differences that the camera will discern, giving you slightly different color balance, from scene to scene as your white source changes. You can buy a Kodak gray card at any photo store, which has 18% gray on one side and white on the other. This will give you a good white standard to use. There is also a new card coming from Kodak, called the "Gray Card Plus." It contains white, black, and gray chips on one side. Besides using it to white balance, shoot a bit of footage under your scene lighting, then correct the footage in post to the proper levels. Then adjust the levels to create your "look."

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