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white balance vs, gray card
Old 10-24-2003, 08:38 PM   #1 (permalink)
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Talk to me about white balance in digital photography.

Tom Snyder

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Re: white balance vs, gray card
Old 10-24-2003, 08:58 PM   #2 (permalink)
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White balance tells your digital camera what is "white." Once determined, all the other colors are set. One trick we used to use with video cameras when shooting people for interviews was to put a light blue gel over the lens while setting the white balance. This forced the camera to adjust and gave the overall image a warmer look.
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Re: white balance vs, gray card
Old 10-24-2003, 09:33 PM   #3 (permalink)
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Okay.
Is it the same as what a gray card means to my film camera ?
With film, metering on a gray card makes color vibrant and real.
If I ever own a digital camera, could I meter an exposure reading
on white card, and get a simular result ?
Tom Snyder
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Re: white balance vs, gray card
Old 10-25-2003, 06:51 AM   #4 (permalink)
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Hi:
No, white balance has nothing to do with exposure. Rather it is a reference for the camera to know the light temperature so that white is recorded as white rather than yellow (incadenscent/warm) or blue (tungsten/cold). For example it means you can totally negate the "golden hour" effect of warm late afternoon sunlight or the coolness of early morning sunlight just by adjusting the whitebalance on a digital camera video or still.

Whatever light source your under, you just point the camera a a white object, such as a sheet of paper for example and hit the whitebalance control and from then on the camera makes the proper adjustments. It like having smart film in a camera if that makes it easier to understand. No need for daylight film, tungsten film and a lot of color temp filters.

This begs the question of how you get a slightly warmer color in your pics if the camera insists on balancing for pure white? You can do it through filters or by shooting a card that is something other than pure white. Years ago we used to use off color paper, but there is a product out there now I think called warm cards or something like that which is a set of colored cards you can use to whitebalance a camera for the effect you want.

Now the 18% reflectance card is just a handy reference for getting exposure right. It mainly gives you an average reference of reflectance when determining exposure settings. I think it loses a bit of its appeal with digital since you can see what is going on immediately but it still has use when setting up.

Hope this helps.
Rick

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Re: white balance vs, gray card
Old 10-25-2003, 08:35 AM   #5 (permalink)
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Use the white card to set the custom white balance on the camera. You can use Warm Cards instead if you want a warmer color balance.

Now having set the white balance, take a photo of the gray card (fully filling the frame with it) at what you feel is a good expousre setting. Look at the histogram of the photo. There should be a spike in the middle and not much else anywhere on the histogram. If its not in the center, adjust the exposure and shoot again till it is near the center. You now have the correct white balance and the correct expousre for the current lighting situation.

Here's a colorful photo to brighten up this discussion:



Cheers,
rfs
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FINALLY!!!!!!!!^^^^^
Old 10-25-2003, 10:31 AM   #6 (permalink)
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somebody got it right!

I am so tired of reading threads that say..."WB off a grey card"


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Re: FINALLY!!!!!!!!^^^^^
Old 10-25-2003, 11:03 AM   #7 (permalink)
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Sorry Clint, but I've been using a grey card for 3 years for WB and I know many pros who do the same thing. It's hard to argue with the results.

Marc
 
 
Re: FINALLY!!!!!!!!^^^^^
Old 10-25-2003, 12:01 PM   #8 (permalink)
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A whitecard has nothing to do with white. Itís all about neutrality. The WB is the cameraís reference to neutral, thatís why you can measure the WB with a greycard. A greycard is even better, because the CCD can make a better measurement.
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In Retrospect
Old 10-25-2003, 09:34 PM   #9 (permalink)
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Is WB a filter built into a camera ?

A gray card is all about neutrality.
A film camera exposure is set to gray.
I still shoot film.

All to often I see digital images that discount
the time of day, clouds, sun and all other factors
that pertain to a real enviroment.
They do not present real world images.

I am confused, and will continue to shoot film,
metered on a gray card, with a Minolta Spot meter.

I did receive some good input in this forum line.

Does anyone believe, a cheap camera, a good lens,
and exact metering make a good image ?



Tom Snyder
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Re: In Retrospect
Old 10-26-2003, 06:27 PM   #10 (permalink)
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Your example seems to have a magenta cast to it. It really makes no difference if you metered against a gray card using a Minolta meter or any meter. That metering did not affect the color cast of the photo. On film you would need a filter to deal with the cast. In Digital you use custom white balance do deal with color casts. The procedure I described earlier for digital guarantees a perfect color balance for the given light and a right on exposure. By the way, if you use a gray card to do the white balance you will not get the same results as using a white card. Virtually every digital camera guide specifies doing the custom white balance with a white card. Now perhaps that is because a white card is always white and gray cards vary so much (13% to 18%).
Cheers,
rfs
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