Light is made up of color, thousands of them in fact. We often don’t realize this because we’re so used to “white light”. If you’ve ever seen a rainbow that is a refraction of all the different colors of “white” light, even the ones you can’t see like ultraviolet and infra-red. White balance is something many people don’t understand. They set it to “auto” in camera and forget about it. As one of the easiest things to correct in post processing a lot of photographer’s take the approach that it doesn’t even matter.
White balance refers to unrealistic colors in a picture so that a person is rendered “hot” or “cold” because of a blue or orange tone in the image. This is referred to as the temperature. It is a combination of tint and temperature based on the wavelength of the light and the intensity.
All light is on a color spectrum from cold (blue) to warm (red) with daylight (white) being in the middle. Light is measured in Kelvin, a measure of temperature. 5000K is neutral or white light while 3000k is for red tones and 9000k is for blue tones. Daylight and tungsten lights mimic daylight in their color temperature which is why they’re preferable for photographers.
In camera you’ll have a menu to adjust white balance depending on the type of lighting you’re using with about 5-10 different options. Most of these presets have a combination of temperature and tint shifts to match the light and “fix” any color tones. A custom set white balance allows you to determine the number by use of a gray card which helps the camera identify the color tones based on a known gray tone for reference.
Using RAW is the best way to deal with white balance because it allows for more control when fixing any issues in post processing.
Neutral Reference or Gray Cards
While a gray card is the best way of getting a neutral reference, choosing an object within the viewfinder is often the best way of getting the camera to automatically choose the right tone. For example, a seagull or a gray brick that shows tones and colors that include black and white. Common items that work are things like Pringles lids, coffee jar lids, anything that comes in a milky tone of plastic. You can also buy gray cards to use or things like an ExpoDisk which measures light and can be used to apply the settings to the camera manually.
If you’re doing things this way beware of any situations which require high noise. Noise often introduces color issues and with higher noise you’re more likely to have color issues because of the frequency the camera is trying to duplicate so it “guesses”.
Most people simply leave their camera set to auto white balance so any fixing is usually a simple slide on the temperature scale in Lightroom or a hue adjustment in Photoshop. The issue is that when you have mixed lighting this often leaves only part of the image with the right coloring. The easiest way to get around this is to use an adjustment brush to fix the white balance of one of the areas and split the image.
Fixing the white balance “in camera” can be done either by switching the preset mode depending on the lighting situation, using a gray card, or simply sliding the white balance slider in post processing.