White Balance Sheet

Question

Level 2

330 points

White Balance Sheet

hi guys,
this thread is addressing/asking you pro-product photographers...

to allow a perfect white balance, i have shot photos with a page having white, grey and black references on it in the image, then cropping it. however, i have lost the page and i have no idea where i have that file. instead of creating a new one - do you guys have such a document handy to share (pdf or so) so it can be printed and be placed in the photo at the next shooting?

or do you use other/pre-produced reference cards?

in case you don't have such a document - would anybody be interested if i create one and share it here? let me know.

G5 Dual 2, Mac OS X (10.4.6), 6GB ram, 30" + 23", X800, 1.2tb RAID, Aperture 1.1.1

Posted on May 9, 2006 12:33 AM

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Answer 1

May 9, 2006 4:10 AM in response to steebow

The reason a grey card is useful is that it is a known neutral colour combination. By taking a sample grey card shot in the lighting conditions you are about to shoot in, you can determine the ambient colour temperature.

By white balance adjusting this sample card shot you have a template to apply to the real shots you will take in that exact setting.

Be warned, there are many, many situations where the grey card trick is not perfect. For example, indoor arenas use sodium lighting that flickers on and off depending on the alternating current. If the lights are not wired properly, they can be out of synch some on some off. Same grey card test shot - 3 different temperatures.

The point is you can assess the reflected light off a known surface, your grey card you carry around in your kit.

Michael

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Answer 2

May 9, 2006 4:18 AM in response to Michael Tooker

Sorry - forgot the crux of the reason.

Therefore you want a purchased grey card that is exactly neutral, not one that was created from a photo.

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Answer 3

May 9, 2006 5:30 AM in response to steebow

To dig further, you do not want a Kodak grey card or similar. That's old school and the problem with them is that they are tone neutral but not color neutral. They were made for camera meters which do not see color and are only concerned about 18% grey for exposure metering.

You want a digital grey card, something like these:

http://www.rawworkflow.com/products/whibal/index.html

http://www.rmimaging.com/ "Digital Grey Card" (also sold at other retailers like Calumet)

or a MacBeth Color Checker and you use the second brightest square in the black to white row for white balance

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=3 25035&is=REG&addedTroughType=search

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Answer 4

May 9, 2006 3:02 PM in response to Jon Roemer

Here is the tip of the day:

If you want a supply of free disposable but very good white balance sheets go to HOME DEPOT or any other store that sells BEHR Premium Plus paints and grab 3-color sampler strip 3B44: Statue Gray 3B44-2, White Silence 3B44-1, Oil Shale 3B44-6.

All three of those swatches are very neutral. The Statue Gray comes out with L ab values of 82.6, 0.4, 0.7. You probably won't get much closer with an expensive MacBeth color checker--though you should probably own one of those too.

Throw about 50 of those BEHR samples in your shopping cart and stick a few at a time in your camera bag. Toss them out when they get soiled and get a clean one to start over. What the heck...they're free!

Just call me digital imaging's answer to Martha Stewart (but don't lock me up).

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Answer 5

May 9, 2006 5:00 PM in response to thomas80205

Here is the tip of the day:

If you want a supply of free disposable but very good
white balance sheets go to HOME DEPOT or any other
store that sells BEHR Premium Plus paints and grab
3-color sampler strip 3B44: Statue Gray 3B44-2,
White Silence 3B44-1, Oil Shale 3B44-6.

The problem is that they might not be neutral all across all light sources and the samples may not be consistent when viewed against each other.

I'm a professional. I would never go the BEHR route. The whi-bal cards or the robin myers cards are relatively inexpensive and the best way to go if you don't want to pay for a MacBeth Color Checker.

Aperture is a professional tool. It doesn't make sense to skimp on this.

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Answer 6

steebow Author

Level 2

330 points

May 9, 2006 6:29 PM in response to Jon Roemer

hi guys
thanks for all the input. my problem is that it's pretty hard to find the products you have mentioned here in australia. no b&h photo here etc. will see if i find a photo-pro shop that imports these products.

while it is not the professional or accurate way, i have had quite good results with a simple "self printed" page (printed with black ink only) holding 3 gray values, an "off-white", a middle gray and a "near" black. with these (especially the 245 white and the gray, i got pretty accurate colours in photoshop (using levels). so for the "no budget" solution, this was pretty good already.

guess, i will create such a document again and share it here for those, who are happy with a "quite ok" (yet not 100% pro solution of course). at the same time i will see if i can find the products you have mentioned and once i have it, i'll let you know how the comparison turn out.

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Answer 7

May 9, 2006 7:55 PM in response to Jon Roemer

Jon,

The problem is that they might not be neutral all
across all light sources and the samples may not be
consistent when viewed against each other.

I have about $150 worth of 'professional targets' and I use them when I can. If I am getting in someone's pickup to go shoot a cattle roundup and can only take what's in my backpack or the target needs to go on a fencepost where it may get distroyed then I pull out the BEHR card.

I have measured quite a few with a Eye-One (which is a full spectrum photo-spectrometer that accounts for metamerism) and they are pretty consistent. No worse than the variations that I measure on Greatag Macbeth color checkers.

The White Balance setting is not so precise in most photos. Unless you work in a well controlled studio all the time the paint cards are good enough for my 'professional' work.

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Answer 8

May 9, 2006 8:49 PM in response to thomas80205

Jon,

Sometimes I am totally off base with a suggestion so I pulled my BEHR paint cards and a Gretag Macbeth color checker and compared the Statue Gray to Patch #2 (one step below white) on the Color Checker.

I measured the 380nm to 730nm visible range and compared them using Gretag Macbeth Eye-One Share software. For metamerism (change in color in different light sources) they are indistinguishable. Here are the L ab values for additional comparison:
BEHR 82.3, -0.1, -0.3
GMCC 81.1, -0.6, 0.0

While your point that the paint cards may vary batch to batch I think they are well up to the standards needed for most uses, they meet the <1.0 ab variation standard of the WhiBal cards and have I will probably buy one of those and add it to my set of references (I'm a color geek), but I will continue to use my free disposable Behr card when that makes sense.

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Answer 9

May 10, 2006 12:28 AM in response to Jon Roemer

Hey Jon, thanks for the gray card info. I found that very helpful. I'll be passing that on to the other photographers I work with.

Steven Georges
Press-Telegram

PowerBook G4 Mac OS X (10.4.6) Photojournalist - homepage.mac.com/daddysteve

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Answer 10

May 10, 2006 6:36 AM in response to thomas80205

While your point that the paint cards may vary batch
to batch I think they are well up to the standards
needed for most uses, they meet the <1.0 ab
variation standard of the WhiBal cards and have I
will probably buy one of those and add it to my set
of references (I'm a color geek), but I will continue
to use my free disposable Behr card when that makes
sense.</div>

Makes sense to me!

Jon

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Answer 11

May 10, 2006 6:52 AM in response to Steven Georges

Based on your suggestions I’m going to pick up a digital grey card, but what do I do to adjust the white balance with the photos I’ve already taken?

I’ve tried using the WB eyedropper in Aperture to pick a neutral grey area in the photo to set the WB. However, the results I get seem very random and I’m often unsure about what area of the photo would qualify as “neutral grey”

Are there any tips for finding the right area on a RAW photo to sample with the eyedropper for WB?

Ken

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Answer 12

May 10, 2006 12:37 PM in response to krwilkins

You are raising a thorny problem. First if you are shooting in a place where you know in advance there will be no neutrals then try to make a shot at the beginning with a white paper business card or some other neutral. The White Balance won't change so much from shot to shot.

You need to find something in the image that you 'know' to be nutral. About L level 80 or higer works best for me but I have seen others in this forum reccomend more medium grays. but not so high that one of the channels is clippiing at 255.

If there are no neutrals and also no skin tones in the images your WB can be pretty subjective (far from the actual scene) and it will look OK. Aperture has the auto adjust RGB button that will stretch the three histograms seperately to fill the full tonal range. I think that it was Andrew Rodney who published that as the 90% rule (it works 90% of the time).

For some reason adjusting the three histograms in Aperture doesn't work as well for me as it does in Photoshop when I use the Auto Levels - separate command. But adjusting the R, G, and B channels manually using the Levels adjust still gives a good result.

I find that there are really very few images with no neutrals for the WB clicker to latch onto, less than 5% for my shooting.

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Answer 13

May 10, 2006 12:43 PM in response to thomas80205

You are raising a thorny problem. First if you are
shooting in a place where you know in advance there
will be no neutrals then try to make a shot at the
beginning with a white paper business card or some
other neutral. The White Balance won't change so much
from shot to shot.

You need to find something in the image that you
'know' to be nutral. About L level 80 or higer works
best for me but I have seen others in this forum
reccomend more medium grays. but not so high that one
of the channels is clippiing at 255.

If there are no neutrals and also no skin tones in
the images your WB can be pretty subjective (far from
the actual scene) and it will look OK. Aperture has
the auto adjust RGB button that will stretch the
three histograms seperately to fill the full tonal
range. I think that it was Andrew Rodney who
published that as the 90% rule (it works 90% of the
time).

For some reason adjusting the three histograms in
Aperture doesn't work as well for me as it does in
Photoshop when I use the Auto Levels - separate
command. But adjusting the R, G, and B channels
manually using the Levels adjust still gives a good
result.

I find that there are really very few images with no
neutrals for the WB clicker to latch onto, less than
5% for my shooting.

Thanks for taking the time to explain.

What does “About L level 80” refer to? Is this on the RGB readout?

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Answer 14

Hud64

Level 1

20 points

May 10, 2006 7:15 PM in response to thomas80205

Thanks for the tip. For some of my needs, I believe the Behr solution would be adequate. Those who need to guarantee a more accurate card value know who they are and can spend the money if they choose (they most likely already have). But I for one will be making use of your tip on occasion. Thanks.

dave

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Answer 15

May 10, 2006 8:44 PM in response to krwilkins

On the RGB readout there is a L value "Luminosity". Its a 0~100 scale, 0=black 100=white. My belief is that a white-point set to a spot with higher lumiosity will be more accurate, as long as none of the RGB channels is at 255.

The L value comes from the L ab color space.

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