Don’t use white paper for white-balance (with examples)

Started Jul 16, 2011 | Discussions thread
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Don’t use white paper for white-balance (with examples)
Jul 16, 2011

There have been a few threads recently on white balance and the value of (relatively) expensive white-balance reference cards vs. plain white paper. So here’s are a couple of examples of custom white balances using both references, and then I’ll explain what’s going on.

In this set of crops the WB reference is included.

First, let me note that the half with the gray reference has the correct color. If you check the RGB values of the references you’ll see that the values are nearly the same within each reference, yet the color of the clock is very different. Before I explain why, I want to say that I understand the idea of adjust WB afterwards and of setting a WB that one finds pleasing. But there are also photographs that need to be as accurate as possible. And even if I want to have a color cast, I still want to see as accurate an image as possible first, as a reference point (and personally, I don't add color casts with white balance tool...I'll use other photo editing tools.)

The half of the image with the white reference demonstrates the problem with using white paper that contains Optical Brightening Agents (OBAs.) The clock has an obvious yellow cast. That’s because OBAs take invisible ultraviolet light and converts it into visible blue light. The blue makes the paper look “cool” or more white in most indoor lighting situations (outdoors it looks blue in shade.) The extra blue is throwing off the custom white-balance process, and causing the camera to reduce the amount of blue in the image. This creates a yellow cast.

So if you prefer to set a custom white-balance in the camera then it really is worth it to spend the money on a proper reference that is spectrally neutral, like a Digital Gray Card, Whibal, ExpoDisc/ExpoCap, Digital Grey Kard, and others. If you use anything else you risk adding an undesirable color cast to your image.

You spent a thousand bucks (or more) on a camera and lenses...it just doesn't make sense to me not to spend another 15 to ensure accurate colors.

.

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