Whitebalance |
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Different sources of light produce light of different nature. The human eye
compensates these differences quite good and we recognize i.e. a white surface
as white under most situations. With analog cameras you have to use the right
film-material depending on the available light or you can compensate with
color-filters.
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Normal film for daylight needs a clear sky and brightly illuminated
objects for proper colors. Under a clowdy sky or in the shadow images getting
blue, red under artifical light and green under neon.
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Within the digital world the whitebalance is responsible to compensate
different light conditions. In auto-position your camera always tries to
guess the right whitebalance depending on the image taken. To make this
work, the camera must have a gray or white object somewhere within the
scene and must properly detect it. If there is nothing neutral in your image,
automatic whitebalance can't work as expected:
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This image is a panorama composed of five single exposures with tight transitions
so the problems are clearly visible. Did you guess the right cup is yellow and
not green? And the color-changes of the wooden folding rule are obviously too.
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Therefore I mostly never use auto-whitebalance, so that images of a sequence
match in color. You can use one of your camera's presets or make a manual
whitebalance on a neutral surface. The correct panorama with a fixed, manual
whitebalance would look like this:
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