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Old Jul 16, 2004, 4:43 PM   #1
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I must really be asking tough questions lately. Not replies. Hmmm.

I'm shooting some marble and granite slabs that are stored vertical and in rows. The main problem is the stone behind me gets reflected in the stone that I'm shooting. I figure I can hang a black fabric behind me to help with that.

The lighting is tricky too. The colors are tough to get right without much Photoshop work. I have an 18% gray card and was wondering if this can help me get better color balance?

Anyone? Anyone? Beuller?

:-)
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Old Jul 16, 2004, 6:48 PM   #2
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The way the White Balance setting works in the EOS digital is that you should take a picture of the 18% gray card under each of your lighting conditions (hopefully just one), and recall this picture(s) as your reference during the Custom White Balance. ie the camera is calibrated to the absolute reference of your gray card regardless of the color of the marble or granite slabs.

The other way is like you already know shoot in RAW and set the White Balance during the conversion or fix it in Photoshop. BTW you can also include the grey card in a corner of the picture so you can easily match it during post editing
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Old Jul 16, 2004, 7:00 PM   #3
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Hey I have an idea, if you want to check the white ballance shoot a white card and save the grey card for it's intended purpose, setting the exposure. That is what I would do anyway. Different strokes, more than one way to skin a cat!
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Old Jul 16, 2004, 9:39 PM   #4
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HawkEyes wrote:
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Hey I have an idea, if you want to check the white ballance shoot a white card and save the grey card for it's intended purpose, setting the exposure. That is what I would do anyway. Different strokes, more than one way to skin a cat!
I've always wondered about that! Sounds logical you take a white card to set the white balance. I think the 10D manual even mentions that....

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Old Jul 16, 2004, 10:58 PM   #5
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HawkEyes wrote:
Quote:
Hey I have an idea, if you want to check the white ballance shoot a white card and save the grey card for it's intended purpose, setting the exposure. That is what I would do anyway. Different strokes, more than one way to skin a cat!
Actually the back of the Kodak's grey card is white... :-)


barthold wrote:
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I've always wondered about that! Sounds logical you take a white card to set the white balance. I think the 10D manual even mentions that...
For White Balance, it does not matter... I argued for a white piece of paper before as the manual state, but it only affects the brightness (ie needed for the exposure). The white balance is still correct with a grey card. You should try it sometime...
Beside which white sheet of paper are you going to use, super white or regular white?

FYI: http://www.photoxels.com/tutorial_white-balance.html
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Old Jul 17, 2004, 9:16 PM   #6
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NHL, thanks for the link. It doesn't explain why setting the WB on a gray card actually works. It just mentions it can be done. Any idea why that works?

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Old Jul 17, 2004, 11:54 PM   #7
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barthold wrote:
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NHL, thanks for the link. It doesn't explain why setting the WB on a gray card actually works. It just mentions it can be done. Any idea why that works?
What color is your white card (or sheet of paper) when you turn the light off in a darkened room?
Grey is anywhere between black and white (18% in this case)... The color is still neutral that's why the WB works. :idea:
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Old Jul 18, 2004, 9:49 PM   #8
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Barthold,
The reason the grey card works is that grey is made up of equal levels of Red, Green and Blue and that is by definition when "White Balance" is achieved. However, not all things that look to your eyes grey are actually balanced therefore be sure to use a standard calibrated card.
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Old Jul 19, 2004, 5:30 AM   #9
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There's multiple shades of gray :-):
http://www.pictureflow.com/products/whibal/

... if you click on the comparison chart some white (ie copy paper) are not too neutral either!
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Old Jul 19, 2004, 12:58 PM   #10
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OK, I have some shots taken with my gray card in the photo and done in RAW format (10D). What's the best tool to use to balance the image based on this gray card? There's an auto selection in the Photoshop RAW window which seems to come out nice. What other tools are there? I've use the midtones eyedropper in the Levels dialog box in the past with good results too. What about the color values (numbers) when I put my cursor over the gray area? Where should they fall?

Thanks.


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