Welcome back from the weekend! How did you do with Weekend Experiment #2?
White Balance is your camera’s attempt to make white = white and thus, accuracy in all the other colors. That’s really all it is. The camera knows if it can make white show as white, all the other colors will be accurate.
White isn’t always white because not all light is created equal. For instance, a tungsten incandescent light bulb (the standard light bulb for the last 100 years, more or less) puts out light that is slightly more yellow/orange than the sun at noon. The measurement of this light is as a function of its temperature on a Kelvin scale, noted with a K.
Degrees of Kelvin and Discoloring
Direct noon-day sunlight is the standard bearer of this scale for reference sake. It is pretty much at 5000K. Anything higher than this color temperature takes on a blue color and anything lower takes on an orange/yellow color.
Back in the days of film you bought a roll based on the light you anticipated using. Most film is daylight balanced, around 5000K-5500K. Do you remember using that film indoors with tungsten light bulbs? Things took on a yellow color cast.
And florescent lights? Greenish yick. This is also why flashes are set at 5500K, they are close to daylight, which is very handy when used as a Fill Flash (a post coming this month).
Light on a Scale
Digital cameras have the advantage of adjusting on the fly for light coming in. But it’s a tricky business trying to guess the light source properly. Therefore, most cameras have the ability to manually change the white balance if desired. Here is a graphic representation of the various settings you might find and their relative value and place on the Kelvin scale.
Why is this Important?
When shooting JPEG files, the white balance is set when the file is compressed. No going back. If the camera picked the wrong white balance, the image is probably too blue or orange or green. And that sucks.
One way around this is shooting in RAW mode because the white balance is not hard set (we discuss RAW and JPEG a another post). When viewed on a computer the white balance information is re-read and applied, but if the white balance doesn’t match, you can simple tell the computer (either by a slider or by typing in the Kelvin temperature) what the white balance should be.
Try it yourself. Grab a white piece of paper and set your camera to daylight (5000K). Get the white piece of paper under an incandescent or fluorescent bulb and snap a photo. Even on the back panel LCD you will notice the color looks off. Off as in white is not white.
Take the piece of paper out into the daylight (if you have it) and perform the same test. Bingo, white is now white and all other colors are accurate.
If you don’t want to worry about White Balance, shoot in RAW and set the camera to Auto for the actual White Balance. Otherwise, if shooting in JPEG, be careful around harsh situations when the camera might get tripped up, such as:
- Moving from direct sun to shade, especially with snow
- Going from indoors to outdoors
- Multiple light sources. In this case, you have to pick one and accept the others source(s) will show as exaggerated
- Large surface areas that are barely offwhite to start with
- High school gyms
- Underwater (but this is a slightly different reason and why a number of point and shoots have a separate setting)
And check to make sure your camera is metering correctly.
One More (Advanced) Thing
You can set a custom white balance if you know the light will be a certain temperature for a certain period of time. This usually involves pointing the camera at something white and using a custom function, so you’ll need to look up how to set it in your camera manual. I know, homework. But it will help if you must shoot in JPEG and have some tricky light.
If you are looking for more in-depth info or a chance to get totally lost, check out Color Temperature on Wikipedia. It was also suggested to me there is a great explanation in the book Understanding Exposure.
Next Up: How To Take A Shot
Questions? Pop ’em like Pez in the comments section below. or email me at firstname.lastname@example.org.
Photography Basics – A 43 Day Adventure, and its companion 40 Photography Experiments, are series written by professional photographer Peter West Carey. The series are designed to unravel the mysteries of photography, helping you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.
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