The primary benefit of setting the correct white balance on your digital camera is that the white areas of your photos will be truly white and the colors will be true and precise. When the white balance isn’t accurate, the white areas can take on a slight orange, blue or yellow tinge and the colors of your photos are not exact. This problem becomes more noticeable if you enlarge the image for printing or view it on an HD monitor or TV.
Setting the correct white balance is a two-stage learning process. First is an understanding of the scientific principle that various light sources are measured at different temperatures and those temperatures relate to a specific color on the visual spectrum. The second stage is to understand your camera’s white balance mode and how you control it.
Light = Temperature = Color
You can thank two scientists of the past, Max Planck and Lord Kelvin, for causing you to relive your high school physics class in this section of this article (Maybe, you’ll listen this time!). The Kelvin temperature scale is similar to the Fahrenheit and Celsius scales; however, Kelvin specifically applies to color. A major difference is that the bottom of the Kelvin scale is absolute zero, which is –459.67 degrees Fahrenheit and –273.15 degrees Celsius.
The principle is rather simple. It starts with looking at a graphic representation of the spectrum of colors visible to the human eye. The left end of the spectrum is deep red, which progresses from orange, yellow, green and blue, with violet at the right end. Think about how the color of the light of an object or substance changes as it becomes hotter. An easy-to-understand example is a log burning in a fireplace. The edge of the log glows reddish or orange, which is often described as red-hot (although this is considered cool in relation to the Kelvin scale). Later, as the wood continues to burn and becomes coals, some of it will look white. Now, it is white hot, which is significantly hotter than red-hot.
You can leap from this principle to the real-world light in your photographs. There are many light sources you might use to illuminate a photo: sunlight, a flash unit, tungsten light (light bulbs), florescent light, etc. Each source produces light at a different temperature, therefore at a different color on the visible spectrum. For example, outdoor light and fluorescent lighting are in the blue, or cool, area of the spectrum, while incandescent light bulbs (tungsten) and a candle are in the yellow, or warm, area. The exception is midday sunlight. It’s light is balanced across the entire spectrum, which is the white balance you are trying to achieve in all your photos.
White Balance in Your Camera
Part of the technological magic of your camera’s sensor is that it can determine how much red, green and blue light (which generally covers the entire visible spectrum) is being produced by the light source you are using. If not enough of one the three colors of light is registering on the corresponding section of the sensor, then that section accepts less of that light color, so the light is balanced.
Most digital cameras have an auto white balance function, which is capable of giving you excellent to acceptable white balance under “conventional” light sources. Digital cameras have a selection of presets that correspond to different light sources. Examples of pre-sets are a light bulb icon for incandescent light, a narrow rectangular icon for florescent light, a sun symbol for sunlight, a cloud symbol for a cloudy day and a graphic representing the shade of a building.
These pre-sets are not absolutely accurate. For example, the light from a well-used light bulb is not the same as a new bulb. Shooting under extreme lighting conditions or unusual light sources will also often confuse these presets. On these occasions, it’s better to use your camera’s manual white balance mode and point the camera at a neutral gray card, which will achieve an accurate white balance. You can also use a diffuser that attaches to the front of the lens, which causes the light to be distributed evenly across the sensor.
Your other point of white balance control is during post-production. Whatever photo editing software you use will help you adjust the white balance; but you should use the RAW files of your photos, so the software has all the data available to set the correct white balance.
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Photo by PhotographyTalk member Mario Celzner