White Balance

WHITE BALANCE:

Not a racial concept... Photography and Text © 2008 Michael Lustbader

I have to chuckle when I read one pundit or another hold forth on the “new” concept of “White Balance in Digital Photography”. White balance is, of course, not a new concept at all, but one that photographers have been dealing with, in one way or another, since the invention of color film. Whenever you placed a UV, 1A, or 81 series filter in front of your lens, you were dealing with white balance. When you loaded a roll of tungsten film in your camera instead of daylight film because you planned to shoot indoors without a flash, you were dealing with white balance. When you put an FD-L filter on your lens to photograph under fluorescent lights, you were dealing with white balance. So, what does it all mean?

ABOVE: In this photograph of a crab spider on datura, there are three different whites. All three have different casts, but I wanted them to be as neutral as possible, neither particularly warm nor cold. UPPER RIGHT: Green tree frog taking refuge in iris. A “cool-toned” image.

Light, as well as Benetton, comes in different colors. It can appear blue, like the fog of an overcast morning on the Oregon coast, red, like sunset reflected off Navajo sandstone, or bright white, like noon at the beach. Without going into a full-fledged physics lesson, the color of light is measured in degrees Kelvin (written as K, not °K). Think of

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it as relating to the color of iron as it is heated, starting from dull red and ranging to white. (Think of “white-hot” rather than ice to describe “white”, and you’ll be OK).

Ambient light (the natural, available light of your surroundings) influences the apparent color of the object upon which it falls, adding a color cast as it is reflected. (Remember, we “see” things by the light that they reflect). Why then, when we take our yellow beach ball inside, does it appear to be the same color yellow that it did in the bright, glaring light at the beach? Our eyes contain light-sensitive receptors called “cones” that receive and transmit color signals from the eye to the brain. We possess three types of color receptors, red, green, and blue. (As in RGB. Isn’t that a coincidence?) In our brains, color signals are interpreted in the context of experience, and color casts are essentially neutralized. This process allows our eyes to adapt to the particular color of the light in which we view our subject. Our brain, in a sense, lies to us and tells us that white is white, gray is gray, black is black, and flesh tones are “appropriate” regardless of the color temperature of the ambient light. The yellow ball appears to be the same shade of yellow, whether we see it in our living room or at the beach, because our eyes and brain work together fool us into thinking that it is so. Your camera, however, has no such adaptive mechanism. It simply records what it sees. If you take a photograph (an “objective” recording) of a scene, person, or object in different lighting, that subject will reflect the actual color of light with which it is lit. A sleepy butterfly photographed in warm sunrise light in the Texas hill country.

The image on the left is how the butterfly truly appeared; the right hand image is more neutral, rendered by the camera’s AUTO setting. When I brought over the file in Adobe Camera Raw, I made sure to use the AS SHOT setting, not the AUTO setting in the WHITE BALANCE dialog box.

Approximate Color Temperature for Common Lighting Situations: 2000K

Sunrise

3300K

Photofloods

2500–3000K

4000K 5000–5600K 6000K 7000K 9000K

10,000K

Incandescent (indoor) tungsten lighting Fluorescent lighting Daylight, Electronic flash

Bright sunlight Slightly overcast skies Bright shade Heavy overcast

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Hence, Aunt Martha’s face photographed at sunset, instead of appearing pale and rather sickly white, as you and I know it truly is, will appear ruddy orange. Under fluorescent lighting, she may very well have a greenish tinge. Since Aunt Martha is known to be very vain and quite capable of holding a grudge for 30 years (just ask Uncle Fred), we must make sure that, if the color cast cannot be not downright flattering, it is at least accurate. Then we can fall back on, “well, you know that the camera doesn’t lie…” and hope to be off the hook and not cut out of the will. How do we accomplish this? Well, we used to do it with filters and different types of film. In the digital age, we spin the wheels, push the buttons, and follow the blinking lights until we find the “WHITE BALANCE” menu. Generally, most digital cameras will give you a menu of choices for White Balance, usually including: DAYLIGHT FLASH

TUNGSTEN AUTO

CLOUDY

SHADE

FLUORESCENT

CUSTOM

The greatest advantage of digital capture over traditional film-based photography in almost all aspects is the increase in process control. Instead of placing more slabs of glass over the lens and between the subject and the recording medium (and theoretically degrading resolution with each…), we can make adjustments to eliminate many color casts right incamera. In fact, we must do so to avoid color aberrations, which may be quite unpleasant. (Think of Aunt Martha’s green face).

These are self-explanatory and work fairly well at least 85% of the time. Simply judge the type of light in which you are working and change the settings accordingly. “Well”, you say, “What if the sky is cloudy-bright? What if it is very dark, (because I like to photograph tornados)? What if I am photographing underwater?” What if…? You’re absolutely correct. The generic settings cannot cover all contingencies. But don’t panic yet. Your camera manufacturer has not abandoned you, and you still have other options. A mixture of cool and warm tones, this leaf on a lichenclad rock was photographed as a RAW image, and converted in Camera Raw, using the AS SHOT setting. I then used a Selective Color adjustment layer to give a little boost to the reds and yellows, without effecting the cooler tones.

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If your approach is to be totally uninvolved with the photographic process, there is usually an AUTO setting that works surprisingly well in most situations. The camera uses logarithms based upon meter readings to choose what it considers to be an “appropriate” white balance setting. You will notice, however, that many of the better (more expensive) cameras will also provide you with a CUSTOM setting. This allows you to tweak the preset color balance numbers provided by the manufacturers of your camera. Each camera is a bit different in the mechanism by which it accomplishes this, but basically, you are asked to photograph a subject that you know is neutral (a white or gray card that supposedly has no color cast) under the lighting conditions in which you are shooting. The camera will then calculate a setting for you, which neutralizes whichever color cast happens to be present. Left: Cool rendition Right: Warmer rendition.

The actual scene actually fell somewhere between these two.

In addition, some more advanced cameras will even show you an actual Kelvin scale that you can then tweak by the numbers. (As if you could tell the difference between 5600K and 5850K, right?) The downside of having this degree of control is, of course, that you had better remember to reset the white balance when you move to a different set of lighting conditions.

“Hey, you just said that the AUTO setting works well,” you whine, “why not just use it all the time and avoid all the aggravation?” “Well”, I reply calmly, “suppose you WANT a color cast? After all, the purpose of photographing the sand dunes at sunset is to capture that golden light flowing over the sand ripples, right?” You don’t really want to neutralize all color casts. In those situations, many photographers simply use the LCD preview and bracket WB (White Balance) adjustments. There is a way you can avoid all the hassle of white balance selection and maintain optimal quality and control. We will deal with that in the next blog, “Shooting in the RAW”.