6. Advanced
Black level
Δ
G
ΔΒ
Δ
R
R
GB
Image6-53

The objective of input balancing

The objectivein input balancing is to “set” the same black level and the same white level for the three colors of a particular input
source.
Black level setting : brightness
White level setting : contrast
Thes ame absolute black and white levelfor the three colors allows the same reference for Brightness and contrast control of the
picture !
These two references also set the range in which the ADC will work for that particular source ( this explainsals o why each input
balancesetting is linked to a particular source and thus saved in the im age file).

How can it be done ?

Tobalance the three color signals of a particular source there are conditions; in fact we must know the black and the white level of
the source i.e. :
1. thesource in question must be able to generate a white signal, ideally a 100% white (background) full screen pattern
2. thesource in question must be able to generate a black signal, ideally a 100 % black (background) full screen pattern

A

B
Image6-54
White balance : In the projector, we will set the contrast for each color untilwe get a 100% light output picture when projecting a
100% white image (image A)
Black balance : In the projector, we will set the brightness for each color until we get a 0% light output picture when projecting a
100% black image (image B).
Thechangeover from min to max is indicated by the apparition of bright spots also called “digital noise”
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