Cameras don’t take pictures, people take pictures. Cameras simply capture and interpret light, nothing more, nothing less. Your camera has controls that affect how that light is captured and then what is done with that information in order to help it approximate the picture you wanted to take. Both are important in getting the picture you were looking for out of your camera.

Of the settings that affect that conversion process one of the most important is a setting called White Balance (WB). Understanding how this control works is the difference between the picture on the left and the picture on the right, because that's all that changed between the two.

Lighting to most people is a lot like eating sausage: we tend to focus on how much is available and not what’s in it.

Different light sources contain different mixtures of color. Some light, such as an incandescent light bulb, contains more red. Daylight at noon on a clear day has a fairly equal mix of colors. The light in a shady area (again with the sun high in the sky) contains more blue (it has to do with the way light interacts with the atmosphere).

In photography, we use something called color temperature to approximate the colors present in different kinds of light. Color temperature refers to the physical temperature, measured in Kelvins (K), you must heat a perfectly black object (called a blackbody) to get a particular mix of colored light. Low color temperature light is full of red (think of an oven element heating up). As the blackbody is heated further the light becomes more yellow to white. At very high temperatures the blackbody will begin to glow more bluish hues.

Now that we know a bit more about our lighting, we can use that to figure out how white balance works (remember, equal parts of red, green and blue makes pure white):

If we tell the camera that the light on the subject is disproportionately composed of red wavelengths (tungsten), it will lower the amount of red and increase the amount of blue and green in the image to balance the overly red light out to keep our whites white.

If we tell the camera that the light on the subject is neutral (daylight at noon on a clear day), it will make only very minor adjustments to the colors in the image to keep white objects white.

If we tell the camera that the light on the subject is disproportionately composed of blue wavelengths (shade), it will lower the amount of blue and increase the amount of green and red in the image to balance the overly blue light out to keep white looking white.

In short, white balance is used to offset the colorful side effects of the lighting on our subject. We approximate the type of lighting through a color temperature which closely approximates the types of lighting we commonly run into.

So now that you know the white balance control is doing, let's look at your camera to see how to tell it what setting to use. Most cameras will have some if not all of the settings shown here. The icons I've used here are common to all Canon cameras.

There are typically six preset color temperature settings for you to choose from for setting your white balance: tungsten, fluorescent, daylight, flash, cloudy, and shade. These presets represent common types of light. If your scene contains multiple types of light you should normally select the white balance that corresponds to the highest color temperature light in the scene.

If you don’t want to use a preset you may have a few other options available to you: Kelvin, Auto White Balance (AWB), and Custom.

You can use the Kelvin setting to enter a color temperature number directly for the white balance setting. If you are using studio lighting where you know a lot about the lights you are using this is a reasonable way to go.

Now, most people want convenience, and convenience means not having to worry about white balance at all, right? Well, that's what auto white balance (AWB) is for. The camera will look at the scene and try to find something in the scene that is white. If it finds something it thinks is white it'll calculate the color temperature based on the amount of red, green, and blue light detected and set the white balance accordingly. It does this for each picture, so the white balance may change from frame to frame (might be a problem if you plan on composing those pictures into something else later on). It also means you run the risk of your camera not finding a white reference in the picture. When this happens it uses something else to set the white balance which usually results in inaccurate colors in the final image.

Finally, there's custom white balance. With this setting you must point the camera at something that is known to be a neutral color (equal amounts of red, green, and blue). It's safest to use a blank white card or blank white piece of paper to do this. You point the camera at the card, tell the camera to take a white balance reading, and then you're set. This is a good way of setting your white balance if you're going to be taking a number of pictures under the same lighting conditions.

Things NOT to use for a white reference when setting custom white balance: ice, walls, kleenex, your hand, something gray (unless your certain it's neutral gray), the sidewalk, etc. These are all not pure white, and that increases the odds that they're also not neutral (same amount of red, blue, and green light reflected off of them). If you use these things to set your white point you're may wind up telling the camera to misinterpret the lighting on the subject and give your picture a color cast you didn't intend.

So now you know about white balance, color temperature, what the settings on your camera mean, and some guidance on when to use them.

Now comes the kicker:

If your camera supports RAW mode and you use it, you can forget about setting the white balance in your camera ever again.

When you shoot a JPEG file on your camera, the camera takes the information from the sensor, the white balance setting, and then creates an image file with all of the colors shifted around according to the white balance. Although you can tweak the colors in photoshop later, you really can't fully change the white balance once an image has been generated. It simply changes too much about the relative amounts of each color and can cause some information to be lost entirely if not set correctly.

When you shoot a RAW file on your camera, the camera dumps the information from the sensor into a file with little or no processing and makes note of what the white balance was set to at the time. You can later set the white balance to whatever you want when converting the RAW image into a final image.

That means that later on, when you want to convert the RAW file into a JPEG on your computer, you can change the white balance to whatever you want then. However, if you want to use a custom white balance setting, be sure to shoot one frame with the reference card you want to set the white balance on each time you change subject lighting for the session.

The picture shown here is the same image out of the camera that I've just set the white balance to different settings in the RAW converter to show the effects of each setting on the final colors of the frame.

When you convert an image from a RAW file one of the very first things you're going to want to check or adjust is the white balance. You can do this by using one of the presets the conversion software provides and/or use the temperature and tint sliders.

Moving the temperature slider to the left lowers the color temperature used to calculate the white balance in the picture. Because light with a low color temperature contains more red than light with a higher temperature, the software will shift the colors and emphasize blues over reds to keep so whites stay white instead of red-white.

Moving the temperature slider to the right raises the color temperature used to calculate the white balance. Light with a high color temperature contains more blue than red, so the software shifts the colors towards red and emphasizes reds over blues so whites are white instead of blue-white.

Not all light corresponds to a particular color temperature. Fluorescent light is a great example of light this. Fluorescent light contains more green than you'll find in any mix of light represented by a particular color temperature so we need another control for this: tint.

The tint slider adjusts the amount of green or magenta introduced into the picture. This helps account for lighting that does not correspond exactly to a particular color temperature.

Pull the slider to the left and you add ever more green and remove magenta (see how the green curve moves to the right in the graph).

Pull the slider to the right and you add ever more magenta and remove green (see how the magenta curve moves to the right in the graph and the green to the left).

Knowing more about white balance and color temperature will make it easier to set your camera or use your RAW processing software to get the colors you want in your pictures.

Not only will your colors be better when you set your white balance correctly, they'll have better contrast and you'll have fewer problems to correct later on. You'll spend less time fixing pictures and more time taking them.

Finally, don't limit yourself to trying to get the technically correct white balance all the time. Sometimes your pictures will look better if you use a different setting than the lighting would normally call for. Get creative and use different settings to manipulate the colors in your pictures to get a whole new look.

Enjoy!
-Brian