By Don Becker OMP Member #155.
In color photography, the hues and tones of the captured image are significantly influenced by the color of the incident light. This incident light can be described by its “color temperature”, which represents a composite of the wavelengths of visible radiation of which it is composed. For photographic purposes, the most important sources of light commonly used and their color temperatures are shown in Figure 1.
The white balance settings on your camera will cover most of the types of lighting commonly experienced. These settings are usually indicated by symbols or icons. A representative set of such icons used by Nikon cameras are shown in Figure 2, along with the white balances they represent. Other camera icons will often be the same or very similar, with some alternative symbols mentioned in the figure.
Many cameras also have additional white balance controls, which allow the photographer to set specific color temperatures in degrees Kevin (see footnote for additional information on the Kelvin temperature scale). For example, if you wanted to use that capability, you could set your camera at the specific color temperature of 5500 °K rather than at “Daylight”, and you should obtain approximately the same result.
The advantage of using this control is that if you would like your images to be just a little bit warmer or cooler, you can set your white balance to, say 200 °K higher or lower than the icon setting. As indicated in Figure 1, a higher temperature shifts the color towards the blue (“cooler”) tones, while a lower color temperature shifts the color towards the red (“warmer”) tones.
However, keep in mind that the camera control should be set at what the light is, in order to obtain neutral or non-tinted images. So therefore, if I were to photograph something at night in the living room of my home with no supplementary light, just the incandescent light in household lamps, I would generally start out with an Incandescent light icon setting. This corrects for approximately 3200 °K, which is the color temperature of photofloods and quartz/halogen photographic lighting. Probably the image would still be too “warm” (orange colored), because the color temperature of a 100 watt incandescent light is about 2850 °K. So, if I use the color temperature control on the camera and set the color balance setting to 2800 °K, I should be OK.
To test that, shoot a white piece of paper and see if it now looks white, rather than yellow or orange. If you are using 60 watt or 75 watt incandescent lights you will likely need to go down to perhaps 2500 °K in your setting, because lower-watting incandescent lights are more red in color output. You should set the color temperature in the camera to what the lighting temperature is, for a first approximation and then modify the color temperature setting until it looks right.
Of course, you can also look in your camera manual for the method to set your custom white balance for any color lighting situation. Mixed lighting (e.g., both incandescent lighting plus outdoor window light) will usually require a compromise, making you choose which lighting to correct for. Often setting the camera to daylight (or perhaps a little bluer) for the window lighting, and letting the incandescent light be somewhat orange, would be the preferred compromise.
Different brands of cameras may have slightly different color balance settings for each icon, and different people may have different preferences for their images. For example, with my Nikon D3 camera when using Norman studio flash units, I prefer to set my white balance to the Daylight icon rather than the Flash icon because I like the slightly warmer image quality I get from that setting. Generally flash units tend to be a little cooler than sunlight.
Fluorescent light is a totally different animal than both daylight and incandescent lighting. Both daylight and incandescent light are composed of continuous wavelength spectra, differing only in their actual wavelengths which produce their very different color temperatures. Without going into too much technology here, let me just say that fluorescent light is composed of a number of specific wavelength spikes, due to the light being produced by particular atomic transitions between different energy levels of the mercury vapor and phosphor components of the fluorescent tube.
The color temperature of the most common fluorescent lights has been a greenish tint, which used to be corrected with a magenta filter on film cameras, before modern digital cameras had white balance correction capabilities. Other fluorescent lights can sometimes have a reddish tint, and more recently they are often labeled as “daylight fluorescent” because they use several different phosphor components in the tubes to make the average light output close to 5500 °K, even though they are still wavelength spikes and not continuous wavelength sources of light.
Some of the compact fluorescent lighting that I have seen can come pretty close to daylight lighting, although usually somewhat cooler or warmer. In general, when photographing important subjects with fluorescent lighting, the best solution is to use a custom white balance setting made using the specific lighting to be used for the final photographs.
So there you have it, a concise summary of color temperature and white balance settings, and how to use them for your photography. I hope that this is helpful to your understanding of lighting and color in photography.
(Note: The Kelvin temperature scale is also known as the Absolute temperature scale, with 0 °K being the temperature at which all thermal motion of atoms cease (= -273.16 °C and -459.67 °F), and 273 °K the freezing point of water. As a material (such as the tungsten metal in a light bulb filament) is heated it starts out as a dull red, then a bright red, then orange, yellow and even white as it gets to very high temperatures. The visible wavelengths of light emitted from such a filament become shorter (more energetic) as its temperature rises, even going to blue-white and above.)
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