Digital White balance for video and photographers Why is it important?

The camera’s eye vs. your eye When you look at a white object, say the page of a book or a sheet of white paper, it appears white to you regardless of the light source. When lit by an ordinary household bulb, or a florescent light, or outside in daylight it still looks white to your eye. But to the camera’s eye, each of these light sources is different and each produces a tint of color on the white object. And unless the camera makes some sort of adjustment for this variation in light color, a white object will not appear white in your photos, nor will all other colors be true.

White balance and Color temperature Color temperature describes the spectrum of light which is radiated from a light absorbent object with a surface temperature. It is measured in a scale called degrees Kelvin, invented by an Englishman, Lord Kelvin.

Types of light sources using the Kelvin scale

Note how 5000 K produces roughly neutral light, whereas 3000 K and 9000 K produce light spectrums which shift to contain more orange and blue wavelengths, respectively. As the color temperature rises, the color distribution becomes cooler. This may not seem intuitive, but results from the fact that shorter wavelengths contain light of higher energy.

Color temperature Using the color temperature slide, you can search for the best color balance for the photo. If the photo has too much red or yellowish color, lower the color temperature (reduce). But on the other hand, if the photo has too much blue, raise (increase) the color temperature.

Typical white balance settings

Auto/ AWB AUTO (also called AWB) mode works OK with flash and indoors and outdoors. Usually the images will still be fairly blue in shade and pleasantly warm indoors at night. When the flash is on most cameras automatically switch to flash white balance.

Custom Manual, Custom or Preset (sometimes a symbol with a dot and two triangles): This allows you to point the camera at something you want to be neutral and it makes it that way. Read the manual to your camera for specifics. Usually the camera sets itself to what's in front of you. Some cameras also can set themselves to something in an image shot previously. TRICK: Set it pointed at something colored or through a colored filter and your resulting photos will have a color cast opposite the color to which you set it! Set it on something blue and photos come out yellow, set it on something purple and the photos come out green. Point it at something warm and you get cool and vice versa.

Tungsten Tungsten (symbol of a light bulb also called "indoor"): Very, very blue most of the time except indoors at night, for which it looks normal. "Tungsten" is the name of the metal out of which the bulb's filament is made. Even indoors many people prefer the warmer AUTO setting. TRICK: Set -1 or -2 exposure compensation and use this setting in daylight to simulate night! In Hollywood we call this "day for night."

Flourescent Fluorescent (symbol of a long rectangle or Fluorescent tube): Use this if your photos are too green or under Fluorescent, mercury, HMI or metal halide lights as you might find in street lights. It will make other things look a bit purplish. Because of this you may not be able to get the exact color you want under Fluorescent lighting, in which case try AUTO or custom.

Daylight Daylight (symbol of a sun): Bluish normal. Only use it for shooting test charts in direct sunlight.

Flash Flash (symbol of a lighting bolt): Almost identical to cloudy but sometimes redder depending on the camera. Use this the same way. With large studio strobes you probably don't want to use this, since the images may be too red. Try the Daylight setting to match carefully daylight balanced studio strobes.

Cloudy Cloudy (symbol of a cloud): It's a little warmer than the daylight setting and best for most shots outdoors in direct sunlight. Why not the daylight setting? The camera manuals are written by engineers, not artists. The engineers are interested in copying color test charts, not making a good photo. You may prefer things on the warmer side.

Shade Shade (symbol of a house casting a shadow): Very orange. This is perfect for shooting in shade, since shade is so blue. It's also for shooting when you are under a cloud on a partly cloudy day since most of the light is coming from the blue sky. It's also for shooting in backlight, again since the subject is lit more by the blue sky instead of the direct sunlight. TIP: Some cameras skip this critical setting. If so, manually set the CUSTOM preset while in shade (also called one- push, Manual and white card and other things depending on manufacturer) and use this setting in place of the missing shade setting. TIP: You can use this mode even in direct sun to make things look warm and inviting. Try it and you'll probably love it. The SHADE setting is a professional secret for getting great images, pass it on!

RAW By far the best white balance solution is to photograph using the RAW file format, as these allow you to set the WB *AFTER* the photo has been taken. RAW files also allow one to set the WB based on a broader range of color temperature and green-magenta shifts.RAW file format Performing a white balance with a raw file is quick and easy. You can either adjust the temperature and green-magenta sliders until color casts are removed, or you can simply click on a neutral reference within the image. Even if only one of your photos contains a neutral reference, you can click on it and then use the resulting WB settings for the remainder of your photos (assuming the same lighting).

Why is color temperature a useful description of light for photographers? Different settings change the amount of orange or blue color cast, usually to compensate for any cast in the lighting. If you have no blue or orange cast you get neutral whites, which is what you usually get if you use the settings suggested by the instruction book. The Fluorescent settings take out the green from Fluorescent, mercury, HMI and metal halide lights used in your garage, sports stadia and parking lots. Forget about shooting under orange street lights: they'll always look orange because they are orange. White balance only adjusts far enough to make lights that look white to us look white in photos.

Mixed lighting Multiple light sources with different color temperatures may complicate performing a white balance. Some lighting situations may not even have a truly "correct" white balance, and will depend upon where color accuracy is most important. Use your best judgement and really LOOK at your results.