The Basics of Digital Photography: Introduction to White Balance and Color Temperature

One of the things that very few camera manuals cover effectively is the principles of color temperature and white balance. Most manuals, even those that accompany high-end DSLRs from Nikon, are skimpy on telling the photographer how to us the WB (white balance) settings to make properly exposed pictures. Almost everyone has heard the terms color temperature and white balance, but few people truly understand what they refer too.

What is color temperature?

Color temperature is measured in degrees Kelvin, a temperature scale named in honor of the British physicist and engineer, William Thompson, Baron Kelvin (1824-1907). The Kelvin Scale, a variation on the Celsius or Centigrade Scale, placed absolute zero at -273 °K instead of at 0°C. We describe different colors in degrees Kelvin because Lord Kelvin discovered in 1884 that as a "Black Body Radiator" was heated to different temperatures, it emitted different colors. When heat was first applied to the Black Body a dim red color was emitted and slowly moved up through the visible spectrum as the heat increased until it became a bright white light at the highest temperature. Color temperature is simply a more precise way of describing a particular form of light and doesn't describe the actual temperature of the source producing the light. The sun for example has a surface temperature of 5600°C or 5873°K while daylight has a color temperature of 5500 to 6500 °K. on the other hand; direct sunlight has a color temperature of 5000 to 5400°K.

For those of us who got our start in the film era quickly learned the importance of Color Temperature because color film came in two basic types, film color balanced for shooting outdoors and film color balanced for shooting indoors under artificial light. Film for indoor use was balanced for a color temperature of 3200°K while film balanced for outdoor use was balanced for a color temperature of 5500°K. When shooting film we learned very quickly what happened if we used an indoors balanced film outdoors without using the proper color temperature filter on our camera lens, our pictures had an unnatural color cast added to them. The same thing applies to digital photography, we must shoot using the right color temperature of the predominant light source. Some typical light sources and their color temperature are

• Match flame 1700 to 1800°K
• Candle flame 1850 to 1930°K
• Sun: at sunrise or sunset 2000 to 3000°K
• Household tungsten bulbs 2500 to 2900°K
• Tungsten lamp 500W to 1Kw 3000°K
• Quartz lights 3200 to 3500°K
• Fluorescent lights 3200 to 7500°K
• Tungsten lamp 2Kw 3275°K
• Tungsten lamps 5Kw, 10Kw 3380°K
• Sunlight: direct at noon 5000 to 5400°K
• Daylight (sun + sky) 5500 to 6500°K
• Sunlight (through haze/clouds) 5500 to 6500°K
• Sky: overcast 6000 to 7500°K
• RGB Monitor (White Pt) 6500°K
• Outdoor shade 7000 to 8000°K
• Sky: partly cloudy 8000 to 10000°K

Why have I spent so much time on color temperature? You need to have a good understanding of color temperature in order to dial in the correct color temperature when manually setting the WB,

White balance (WB) is the process of removing unrealistic color cast, so those objects, which appear white in person, are rendered white in your photo. Most DSLRs give you a number of options to choose from on the WB Menu. The Nikon D40, for example offers the photographer 8 options to choose from.

• Auto
• Incandescent
• Fluorescent
• Direct sunlight
• Flash
• Cloudy
• Shade, and
• PRE: White balance preset

Other cameras may offer options like

• AWB: Auto white balance
• Custom
• Kelvin
• Tungsten
• Fluorescent
• Daylight
• Flash
• Cloudy, and
• Shade

Auto white balance is recommended for most shooting scenarios. Auto white balance employs an algorithm to calculate a best guess color temperature that fall somewhere between 3000 and 7000°K.

Custom and Kelvin options

If your camera has the "Custom" option, you can take a picture of a known gray card under the same lighting conditions and then set that as your WB for all the pictures you take. The Kelvin option, if your camera has this WB option, allow you to dial in a specific color temperature. To use this option optimally you need a color temperature meter because the color temperature of light sources change as the light source ages. The PRE option of the Nikon D40 is equivalent to the Custom option, allowing you to use a known gray card to set WB. The "Custom" or "Pre" options are best used under studio lighting conditions. To learn how to adjust the WB using a known gray card with your particular camera, consult the user manual.

Your assignment for this lesson is, if you wish to accept, is to take your camera out and experiment shooting pictures using the different WB options available to you. I want you to deliberately shoot pictures using the wrong WB options so you can see what happens to your pictures. Once you have mastered the WB options, you will be able to use these options creatively. There are times when you may choose to shoot using a wrong option because it will create just the effect that you are looking to create with that particular photo.