White Balance in Digital Photography

I’ve been experimenting with all the different settings on my camera. Yesterday’s experimentation focused on the “white balance” control. This is a concept that I never learned when I was doing film photography and since I bought my first digital camera, I have always used the AWB (auto white balance) setting to let them camera decide what the right setting is. So yesterday, in trying to understand how the white balance settings work, I did the following experiment. I was making photos in the late afternoon around my condo. I made the following with my camera set to AWB.

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I wasn’t happy with this image because the bluish hue doesn’t match the golden hue of the late afternoon sun that my eyes were seeing. So I changed the white balance setting to “daylight” and then made the following image. All of the exposure settings for this new image are exactly the same as those for the previous image.

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The colors in this second image much more closely match the colors that my eyes were seeing. Seeing such a significant difference in the two images made me do some reading about the white balance settings. The details of white balance are pretty technical and I don’t understand all of it after my hour or so of reading. But I think I have enough of the details to explain how to use white balance effectively. Of course, explaining and putting into practice are two very different things so I have some work to do!

To understand white balance, you first have to understand that all light has a temperature. This seems intuitive to me since we often talk about the “warm” light that comes from a setting sun. So warm light is yellow while cool light is blue. This cultural association of colors with temperature is actually the exact opposite of the actual temperatures of the colors. The way these temperatures are measured is pretty technically complex but you can read about it at a bunch of different online sources. For me, I think it will be enough for now to remember that full sun in daylight is 5500 degrees kelvin (degrees kelvin–or K–is the measure of temperature). Yellows, oranges, and reds are lower in temperature and greens, purples, and blues are higher in temperature.

When I used to shoot film, indoor lighting was challenging because with most film, skin tones would come out looking yellowish. I had a filter that I would add to the lens to get rid of the yellow in skin tones. This is because most film is designed to capture natural light, in particular, that 5500K light of full sun daylight. So when shooting indoors under artificial light (usually tungsten), there is a lot of yellow in the light but less blue because indoor light has a lower temperature than full sunlight. Without correction, any whites in the scene will appear as yellow in the image. To correct this, I would use a bluish filter over the lens that added blue to the scene which would get rid of the yellow cast.

In digital cameras, we can do this correction in the camera itself rather than having to add a filter over the lens. The idea is to try to get the whites to look white by adding the appropriate color to the scene. This is why it is called “white balance.”

So if we look at the first image above, the one I shot with AWB, there are some parts of the image that actually look white. But the overall image has a bluish cast. The scene that I was seeing was very warm, very golden. Even the whites had a golden cast. The camera added a lot of blue to the image to get those whites to look white. But it is too much blue so that the image doesn’t look anything like what I was actually seeing. When I then captured the scene a second time with white balance set to “daylight,” I was telling the camera that the image was being shot in full daylight so no adjustments needed to be made in order for whites to look white. And this image looks closer to what I was seeing.

But the second image is still not quite what I was actually seeing yesterday afternoon. It isn’t golden enough. So I made a third image with all the same exposure settings but with the white balance set to “shade.” Shaded light is bluer than daylight so the camera added more yellow to try to make the whites white. You can see that the image below is indeed more yellow than my daylight image above. But the color still isn’t quite right.

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If you make your images using the RAW format rather than JPG, you can do a lot of post-processing in tools like Adobe Lightroom or Photoshop to try to get the white balance set so that it accurately represents the look you’re going for. I played around with my image in Lightroom a little bit this afternoon but haven’t yet created an image that I’m completely happy with. As I said, I need to keep working on my understanding of white balance in order to be able to capture the varieties of beautiful light that occur in the world. All of this fiddling around with white balance (and exposure settings as well) makes me really appreciate what an amazing organ the human eye is to be able to capture the subtleties of so many different kinds of light with no conscious effort on our part.

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