White balance is often a misunderstood term for many new to photography. Have you ever taken a photograph with your camera white balance set to auto and for some strange and unknown reason the image had an unusual color cast? If so, the following explanation may help to clear the confusion.

When you manually set the white balance you are programming the digital camera with the color temperature of the light that is illuminating your subject. The temperature of this light is measured in degrees Kelvin.

Without going deep into physics, imagine for a moment a piece of metal heated by a very intense flame. As the metal becomes hotter and the temperature reaches a point where the metal begins to emit light, it will glow with a deep reddish color. As the temperature of the metal increases further the color will change to yellow and ultimately to blue. The hotter the metal becomes, the higher the degrees in Kelvin the color of the light.

These same temperatures and colors of the glowing metal are correlated to colors of light we are all familiar with. The yellow-white color of a common indoor tungsten light bulb is rated at around 3200 degrees Kelvin, bright mid-day white sunlight is rated at 5500 degrees Kelvin as well as most flash units. The color temperature at twilight can exceed 10,000 degrees Kelvin.

Visible Light Spectrum

White mid-day sunlight will shine roughly equally across all wavelengths of light in the visible spectrum. Tungsten light has a greater amount of red and yellow than the rest of the spectrum. Thus, if you took an image of an indoor scene illuminated by tungsten light with film balanced for mid-day sunlight, the scene would appear to have a yellowish cast. Shooting that same scene with tungsten balanced film would make the colors of the subject appear as they would under mid-day sunlight.

Do you remember taking images outdoors of people standing in full shade or under cloudy skies with daylight balanced film? There was that awful blue cast in the developed prints that usually spoiled the photographs. That was because the color temperature in those lighting conditions was somewhere between 6000 and 8000 degrees Kelvin. With slide film, a warming filter was usually used on the lens to compensate and with color film, adjustments had to be made in the filtration pack in the enlarger by a custom lab.

With digital cameras, getting accurate colors became much easier. The white balance can be easily dialed in before the shot is taken for a variety of lighting conditions and can be changed or finely adjusted after the image is taken if shooting in RAW format. On more sophisticated cameras one can set a custom white balance by shooting a white or gray card in the same light as your subject.

Subject Illuminated by Tungsten Lamp; 1st-5300K WB; 2nd-3300K WB; 3rd-Custom WB

So what exactly is happening when you set your white balance to the tungsten setting when your subject is illuminated by incandescent lighting? You are programming the camera to produce an image where your subject will have the color balance as if it was taken in lighting conditions similar to mid-day sunlight.

What do you do if you want to reproduce all those beautiful colors in a morning sunrise? You certainly wouldn’t want to set the white balance to the 3000-4000 degrees Kelvin to match the temperature of the light because if you did, the scene in the capture would more closely resemble what it would look like at mid-day. Shooting at the mid day sunlight setting of 5500 degrees Kelvin would give you all those warm colors usually associated with a sunrise though most likely a bit more exaggerated than what the eye perceived – the eye has a remarkable ability to adapt to changes in color temperature so white still looks “white” or at least close to it, in varying lighting conditions.

Street lamps and some fluorescent tubes introduce a problem when trying to get the colors of your image correct. These light sources don’t emit light across the entire visible spectrum so one can’t really set a white point. There will always be an unnatural color cast of some sort in the final image.

Mixed lighting poses another problem. As an example, in an indoor scene partially illuminated by tungsten light and partially illuminated by sunlight streaming in a window, one has to decide which temperature of light to balance for. There will always be a compromise as part of the scene will be correctly color balanced while the other part will have a color cast.

If you choose to use the auto white balance setting, the camera then has to “guess” at what the proper white balance should be for the light you are shooting in. Some cameras do this better than others though I advise that you not use the auto setting due to its inaccuracies.

So what’s my advice? I recommend that you keep your camera white balance setting at daylight for indoor shots with a flash and for most outdoor shots. If skies are overcast or if you are shooting in shade, use the overcast setting. If you require more flexibility or options you really should be shooting RAW format or if you want to make sure your subject has a color balance similar to what is produced by mid-day sunlight and have the camera option, take a custom white balance reading in the same light as your subject.

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