5D - CWB: prefers a white card over a gray card?

Started Jul 16, 2008 | Discussions
Fawad Junior Member • Posts: 47
5D - CWB: prefers a white card over a gray card?

I attended a flash photography class at Helix the instructor Will Crocket said that for some reason the 5D prefers a white card over a gray card for custom white balance.

Has anyone else found this to be true?

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Kagetsu Regular Member • Posts: 250
Re: 5D - CWB: prefers a white card over a gray card?

Yes, I honestly have. I'll also add, that the Auto white ballance is suprisingly good on the 5D, and even better on the 1Ds III. I'm also using the CWB white/full spectrum disk for my white balance. In fact, the 1DsIII is so good in about 90% of the time, that I didn't really need to use the CWB.

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Ken Phillips Forum Pro • Posts: 16,361
The camera cannot tell!!

Really! As long as it's properly exposed, you can use a white or grey card. (Of course, the card must truly be neutral, unless you want to push towards warm or cool.)

Go out on a nice cloudy day, put the camera in P, and shoot a white target, a black target, and a grey target, filling the frames. Surprise!
KP

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93octane Contributing Member • Posts: 725
Re: The camera cannot tell!!

I'm intrested to find out on this for sure. I currently have a Whibal and it does an OK job and was thinking about picking up a photovision calibrating target. When you say white would white be like a piece of paper???
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luben solev
luben solev Senior Member • Posts: 2,119
Let me guess....

"Go out on a nice cloudy day, put the camera in P, and shoot a white target, a black target, and a grey target, filling the frames. Surprise!"

They all come out mid grey!!!

Luben

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xtoph Veteran Member • Posts: 9,871
more or less

that is, the camera's white balance does perform better when exposed to the top third of the histogram. if you're using manual exposure (which i usually do), then often you will get better results from a white card than from a grey or darker card. eg, clicking the white square on the (cheap) sticker of the (expensive) whibal card sometimes works better than clicking the card itself.

if you're using auto, you want to be sure to dial in some overexposure to get the measured point up higher on the histogram.

Victor Engel Forum Pro • Posts: 17,900
I read this long ago

Well, for digital photography it was a while ago. I'd just recently purchased my 10D. I was puzzled at the time why a white card would be better than a grey card. However, if you think about it, it makes sense. There is simply more signal for a given light level from a white card than a grey card. If you were to increase the light level for the grey card reading, the camera wouldn't be able to tell the difference between the two.
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Ken Phillips Forum Pro • Posts: 16,361
Yeah, if your metering is correct! [nt]
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Ken Phillips Forum Pro • Posts: 16,361
Obviously ...

... you'd adjust the exposure, wouldn't you? It may be cloudy or bright, or inside or out - which may easily affect the amount of light reaching the camera more than the reflectivity of the card.
You should expose the card, grey or white, the same way.
KP

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Victor Engel Forum Pro • Posts: 17,900
Re: Obviously ...

The longer the exposure, the more heat noise from the camera.
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mchahn Contributing Member • Posts: 824
Re: Obviously ...

I'm out of my expertise here, but if the sensors weren't linear, then a white card and a gray card might give different WB results. In other words if you put in light that is twice as bright but has the exact same color, the numbers coming out of the sensor may not be exactly twice as much in each color.

In that case using an 18% gray card would be better since your eyes see color much better in gray than in black or in white. That may be the reason gray cards are usually recommended.

Of course, the sensors in the 5D may be so linear that there is no difference in white or gray, except for the advantage of white putting out bigger numbers (mentioned in an earlier post).

In any case, I seriously doubt it makes any difference in a good camera like the 5D. The actual colors in the light vary so much in a scene that the variation in the calibration method is probably insignificant.

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