My Virtual Canvas

Managing or calibrating your digital cameras white balance is the process in which you are removing the color casts that are “untrue”, so that subjects that appear white to the human eye are white in your photo. Setting a custom white balance yourself on the scene will calibrate the camera to the color temperature of light that is illuminating your subject at the time of shooting.

The human eye (without any existing physical or pathological impairments) is pretty good when it comes to discerning differing levels of “white-ness” under different lighting conditions. The AWB or Auto White Balance feature on Digital cameras and other digital optical equipment however can often have a fair amount of difficulty and prove to be quite inconsistent in its calibrations and can leave noticeable blue, red, yellow or even green hues that are “untrue” to the actual lighting that existed at the time of exposure.

Getting a grip on the concept of White Balance can help improve your photographic skills so you can work effectively and efficiently under a wider array of lighting conditions and reduce or eliminate the existence of these “untrue” color casts in your work.

Color Temperature and White Balance

Before going into the whole issue of white balance we should probably throw the concepts of the “blackbody” and color temperature at you first. Color temperature describes the spectrum of light which is radiated from or given off from a “blackbody” that has the same surface temperature. For our purposes here, a “blackbody” is any item that will absorb all ambient light. The “blackbody” doesn’t allow the light to pass through it nor does it reflect the light back.

Socially, people usually think of red to be hot and blue to be cold. When it comes to the subject of color temperature from a photographic or artistic perception of color temperature, this is a HUGE misconception and leads to general confusion on the issue and difficulties for some students to understand.

My best thought for a day to day analogy might be an intense camp fire. At the base of the fire, where the fire is hottest, the coals can appear to be almost white… so some folks might call this part of the fire “white hot” and a little further out from the center, you might see some blue flames, and further still from the center the flames usually appear reddish-orange. The point being that The center of the fire is the hottest (white) area and the further away from the center you become the more red you see in the flames (the cooler you get).

The issue of color temperature is a means of assigning a value to, or quantifying the color of light. The colors of light are measured in degrees Kelvin (K). The more blue (cooler) that exists the higher the color temperature and the more yellow (warm) the light, the lower the color temperature. The true color temperature of average daylight will fall somewhere between the two.

I was going to include a color temperature chart here but after checking out a lot of different color temperature charts being used in different industries such as that of photography, lighting manufacture, and plant nurseries; I’ve found that they’re all a little different so I’m choosing not to provide an example for you here because I don’t want to mislead anyone (or confuse you further) on the subject. My best advice for better accuracy would be use a good reliable light meter and measure your lighting on-the-scene as opposed to guessing.

Considerations for White Balance Calibration

When manually recalibrating the white balance on your camera you need to use something as a neutral reference unless you have something in your scene to use which rarely if ever happens. There are a handful of things you can use to get your white balance straightened out. The following suggestions should help get you on track.

White Balance References

Resourcefulness in using common household items to solve your daily complications is a good trait to have, even in digital photography. If you check out some of the photography forums on the net and present your white balance calibration question, you might be surprised at some of the answers you might get in return.

Some common items in the home would include coffee filters, printer paper, lids from coffee cans and Pringles potato chip cans, white napkins, pretty much anything that your eyes know to be white. You can use a rubber band to attach your white coffee filter or napkin over your lens and set your white balance. Tape or hold the piece of printer paper in front of your lens. Lids from coffee cans and potato chip cans act as a neutral reference. Not only are these items fairly accurate as references for setting your white balance but they are CHEAP and EASY to come by and also easy to keep with you or in your camera bag.

Store-bought White Balance Gizmos

White and Gray Cards For White Balance

There are a lot of experienced photography enthusiasts out there, along with a lot of pros, that believe that our eyes are easily tricked by make-shift items listed above. Even though the images taken after calibrating your white balance with some of these are of very good quality, I think there is a lack of trust in these devices simply because of what they are. Functional Fixedness is the psychological term for it I believe.

Which ever side of the fence you fall on when it comes to this issue, there are reference cards you can buy (if you feel you need them) to help you calibrate your camera’s white balance. Those doubting folks mentioned above believe that these cards are more accurate in calibrating white balance because they are made specifically for that task. Again, there are those of us that feel that the level of increased accuracy is arguable. These reference cards don’t come cheap either for what they are. So, especially if money is an issue just be honest with yourself when it comes to your need for these.

What the hell is an Expodisc?

These devices are made of special optical grade materials and basically take your camera’s built-in custom white balance function and turns your camera into an incident color-metering tool. They are supposed to work well for calibrating video equipment also.

The standard one looks like a thick filter or lens cap that you snap on the front of your lens. The inside of this gizmo has a translucent white layer and the outside is honeycombed glass. The ExpoDisc comes with a nifty little lanyard so you can keep this thing around your neck for quick access while out in the field. You pop it onto your lens, get a reading, then re-attach it to the lanyard when you’re finished. There are different sizes available but they are a bit pricey so a common thought on the matter is to buy the one that will fit the largest lens in your arsenal and then just physically hold it up against your camera when using smaller lenses. Sounds pretty easy and it’ll save you a few bucks.

Your Camera’s Auto White Balance Function

The auto white balance function in your camera is most effective when the frame contains at least one white element. Of course, do not try to change your composition to include a colorless object, as long as you’re aware that not having one can cause the auto white balance to not calibrate properly. Without a white object in the image the camera’s auto white balance will be mistaken and create an image with a slightly warmer color temperature.

In a setting with mixed lighting, the auto white balance function usually calculates an average color temperature for everything in the frame, and then uses this as the white balance. This approach is usually works out OK, however the auto white balance tends to exaggerate the difference in the color temperatures for every light source, as compared with what we perceive with our eyes.

This exaggeration in color temperatures is usually most obvious in mixed indoor and settings with natural lighting.

This information should help you get your white balance issue straightened out so you can be produce top quality images your next time out.

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