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APPENDIX B – Detailed descriptions White Balance
Parts of this Appendix are taken from the web site
http://www.photoxels.com/tutorial_white-balance.html
If you come from the world of films or single lens reflex cameras, you may remember
using filters to correct for incandescent or fluorescent lighting. Most people don't bother
and their indoors pictures invariably come out with a yellow/orange or bluish cast. In the
digital world, these correction filters are no longer necessary, replaced by a feature found
in most -- even the entry-level -- digital cameras called, "White Balance."
Light Color Temperature
The reason that pictures turn out with a yellow/orange cast in incandescent (tungsten)
lighting and bluish in fluorescent lighting is because light has a color temperature. A low
color temperature shifts light toward the red; a high color temperature shifts light toward
the blue. Different light sources emit light at different color temperatures, and thus the
color cast.
By using an orange or blue filter, we absorb the orange and blue light to correct for the
"imbalance" -- the net effect is a shift in the color temperature.
Manual White Balance
This is where the concept of "White Balance" comes in. If we can tell the camera which
object in the room is white and supposed to come out white in the picture, the camera can
calculate the difference between the current color temperature of that object and the
correct color temperature of a white object. And then shift all colors by that difference.
Most advanced digital cameras provide the feature to manually set the white balance. By
pointing the camera at a white or gray card (angled so that it is reflecting light from the
room) as a neutral reference, filling the screen completely with it, then pressing the White
Balance button (or set it in the menu), the camera does its White Balance calculation.
From then on, any picture taken will have its color temperature shifted appropriately.
A sophisticated user of a Ken-A-Vision camera, might try placing a white card in front of
the camera just before taking an image, and the camera will undergo self white balance
under the extant lights, or in those cameras with manual re-setting of white balance, the
color temperature can be adjusted for.
Automatic and Manual Re-setting White Balance
All Ken-A-Vision cameras provide a preset White Balance setting which works well in
most lighting situations including Tungsten, Fluorescent, Cloudy, Sunny, etc.
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