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10. Settings
Black level
∆
R
ADC
0
255
i1 : superfleous information
i2 : video information
Image 10-22
One can conclude here that a good color tracking can only be met by using three previously (input) balanced
color signals
The objective of input balancing
The objective in 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
The same absolute black and white level for the three colors allows the same r
eference 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 explains also why each input
balance setting is linked to a particular source and thus saved in the image file).
How can it be done ?
To balance the three color signals of a particular source there a
re conditions; in fact we must know the black and the white level of
the source i.e. :
1. the source in question must be able to generate a white signal, ideally a 100% white (background) full screen pattern
2. the source in question must be able to generate a black signa
l, ideally a 100 % black (background) full screen pattern
A
B
Image 10-23
White balance : In the projector, we will set the contrast for each color until we 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).
The changeover (transition) from min t
o max is indicated by the apparition of bright spots also called “digital
noise”
R5976741 MGP 15 MEDICAL GRADE PROJECTOR 28/04/2004 77