Understanding White Balance White balance (WB) is the process of removing unrealistic color casts, so that objects which appear white in person are rendered white in your photo. Proper camera white balance has to take into account the "color temperature" of a light source, which refers to the relative warmth or coolness of white light. Our eyes are very good at judging what is white under different light sources, but digital cameras often have great difficulty with auto white balance (AWB) — and can create unsightly blue, orange, or even green color casts.
Color Temperature Color temperature describes the spectrum of light which is radiated from a "blackbody" with that surface temperature. A blackbody is an object which absorbs all incident light — neither reflecting it nor allowing it to pass through. Blackbodies at different temperatures also have varying color temperatures of "white light." Not all white light has the same temperature. Color Temperature Light Source 1000-2000 K Candlelight 2500-3500 K Tungsten Bulb (household variety) 3000-4000 K Sunrise/Sunset (clear sky) 4000-5000 K Fluorescent Lamps 5000-5500 K Electronic Flash 5000-6500 K Daylight with Clear Sky (sun overhead) 6500-8000 K Moderately Overcast Sky 9000-10000 K Shade or Heavily Overcast Sky
The Green / Magenta Shift Some light sources do not resemble blackbody radiators, so white balance uses a second variable in addition to color temperature: the green-magenta shift. Adjusting the green-magenta shift is often unnecessary under ordinary daylight, however fluorescent and other artificial lighting may require significant green-magenta adjustments to the WB.
Digital Camera White Balance Settings The first three white balances allow for a range of color temperatures. Auto white balance is available in all digital cameras and uses a best guess algorithm within a limited range — usually between 3000/4000 K and 7000 K. Custom white balance allows you to take a picture of a known gray reference under the same lighting, and then set that as the white balance for future photos. With "Kelvin" you can set the color temperature over a broad range. The remaining white balances are listed in order of increasing color temperature. Incandescent light is what most household lighting is. Some cameras also include a "Fluorescent H" setting, which is designed to work in newer daylight-calibrated fluorescents.
Customizing White Balance At most light-specific settings white balance can be “fine tuned” by +/- 3 in increments of one. Choose lower values to make photographs appear slightly more yellow or red, higher values to lend images a bluish tinge.
Customizing White Balance You can use the custom or PRE settings to manually control the white balance on your camera. For a Nikon - With that option selected, hold a white card in front of the lens and press the shutter button. The camera will read and lock in the color temperature of the light reflected from that card, and that locked-in reading now becomes the standard for the camera's white balance setting. PRE is an ideal way to handle a scene that presents mixed lighting—fluorescent lights in the ceiling and daylight streaming through a window, for example—because it takes into account all the lighting in the scene. The locked-in setting is maintained in PRE until you take another white card reading.