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PFWX-51B/PFWU-51B 10/02/2014
46
7.Image
The alterations of the three color signals will happen independently i.e. the colors will end to be unbalanced, image 9-30
B
Black level
0.7V
Image 9-29
Black level
∆
G
∆Β
∆
R
R
G
B
One can conclude here that a good color tracking can only be met by using three previously (input)
balanced color signals
Analog Digital Conversion
The analog color signals must pass through an Analog/Digital conversion circuit prior to any digital processing in the PMP. A
typical ADC transforms the analog value into an 8 bit coded digital signal.
The graphic shows that when converting a signal containing a DC offset component the range of the converter is not optimally
used.
Black level
∆
R
ADC
0
255
i1 : superfluous information
i2 : video information
One can conclude here that a good data conversion 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 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 explains also why each
input balance setting is linked to a particular source and thus saved in the image file).