How do I find a neutral reference to set white balance in a photo?
Asked 10/25/2015
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I understand white balance as correcting the color of the light so objects look as if they were lit by neutral white light. In Photoshop or a RAW editor, the white balance eyedropper is usually used on something that should be neutral gray, white, or black.
My confusion is: how can I know what in a real scene is truly neutral? Is it a good approach to take one reference shot with a gray card or white paper, then use that to set the white balance for other photos taken in the same light?
Also, can snow be treated as a neutral reference? If I sample snow in sunlight versus snow in shade, I get different results. Why does that happen?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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To answer your question about different white balance results from snow in light and shadow: snow that is in sunlight will have a warmer light falling on it, while the light that falls in the shadows is reflected light off the sky, so tends to be more blue, so cooler.
You need to pick something that is not blown out. So snow, if the RGB values are all near 255, will probably not give you much correction - if one or more of the values is blown, then the relative difference in values will not be correct.
In any case, you don't necessarily want to find something that is perfectly neutral, and then correct it fully, because it will take all the warmth out of the image. Often you want that. So it's a subjective thing - find something close to neutral, apply the white balance correction and then use your judgement whether it improves the image or not. If it overcorrects, try another spot, or use the correction and dial it back some until it looks right to you.
Originally by user4191. Source · Licensed CC BY-SA 4.0
user4191
10y ago
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Generated from our catalog & community — verify before relying on it.
Yes—using a neutral reference shot is the standard approach. If you photograph a gray card (best) or a reasonably neutral white paper in the same light as your subject, you can use that shot to set white balance for the other images made under that same lighting.
For the eyedropper, a mid-gray area is usually better than pure white or black, because whites or blacks may be clipped and won’t give reliable RGB relationships.
Snow is not always a good neutral target. Snow in direct sun is lit by warmer sunlight, while snow in shadow is often lit mostly by blue skylight, so they naturally have different color temperatures. That’s why sampling each gives different white balance results.
Also, white balance is not purely technical—it’s partly subjective. A fully neutral correction can remove the natural warmth or coolness of the scene, so you may prefer a result that looks believable rather than perfectly neutral.
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