Experiment of the Week - White Balance

Have you ever taken a photograph indoors and found that all the colors turned out wrong? Everything may have looked far too yellow or far too blue. It was not the fault of your camera. Instead, you probably forgot to set the white balance. What is white balance? Lets find out.


To try this, you will need
- a camera. You can use a digital camera, cell phone, etc.
- different kinds of lighting
- a white object

Start outside, in a well lit area. You don’t need to be in bright sunlight, just enough light to give you a good photograph. Hold a sheet of white paper or some other white object and have someone take your photograph.

Then take the same white object indoors. Find a room where you have several incandescent lights. These are the lights that we normally use in our homes. Again, pose with the white object and have your photo taken again.

Last, find a place where there is bright, fluorescent lighting. Often kitchen lighting is fluorescent. Usually these bulbs are long tubes, but recently, you can find bulbs where the tubes are spiraled, to make them fit into a regular lamp. Once again, pose with the white object and have your photo taken.

The results will vary a lot, depending on your camera. Most cameras have some software built in, to help correct color, but you should still be able to see quite a difference when you compare the three colors. The outdoor shot should have good color, while everything in the incandescent shot will look yellowish, and everything in the fluorescent shot will have a blue tint.

Why don’t you see that with your eyes? Well, actually you do, but your brain automatically white balances what you see. You brain knows that sheet of paper is white, so it color corrects what you see to make it register as white. If you really stop and pay attention, you can see the color difference, but if you don’t really look, you will see the object as white in all three kinds of lighting.

I even found that I could watch my cell phone camera do the white balance. Place a white sheet of paper in a room lit by incandescent lighting. Turn on your cell phone camera and hold it close enough for the paper to fill most of the screen. Watch closely. At first, the paper will look quite yellow, but after a second, the screen will shift, making the paper look white. Your camera just white balanced itself, to make the photo look better.

I just wish that video cameras worked as fast and as well as our eyes. That would make my job a lot easier!

Have a wonder-filled week!

Taken from Robert Krampf Science Education Co.
http://www.krampf.com/index.html
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