Ops 19–8 • Appendix B: Color Correction Parameters Vision Operator’s Manual (v12.0 MD)
RGB Color Correctors
The RGB Color Corrector option provides the following parameters for video signal correction:
• Red, Green, and Blue Gain
• Red, Green, and Blue Offset
• Red, Green, and Blue Lower Offset
• Red, Green, and Blue Gamma
RGB color correctors are provided as an alternative method for modifying color and brightness in
a video signal. The Vision switcher converts the video signal values from Y-Cr-Cb (Luminance,
Chrominance) to RGB. Once any corrections are applied to the RGB values, the switcher
converts them back to Y-Cr-Cb.
The following graph (Figure 19.9) illustrates a single channel (red in this case) of an RGB signal
with no color corrections applied. The horizontal axis represents signal values before any changes
are applied and the vertical axis represents signal values after any changes are applied. The solid
black line running from A to B represents an unmodified video signal where A is the minimum
signal value and B is the maximum. You can look at any point on the line and the output value
matches the input value. This line is represented in the graphs throughout the remainder of this
section to provide a standard which serves to illustrate the effects of various RGB color
corrections.
Figure 19.9 Red Component with No RGB Color Corrections Applied
Gain
Gain represents the range of signal values present in a video signal from a lowest to a highest
point (from 0 to 100% for an RGB component). Increasing the gain expands this range while
decreasing the gain compresses this range. Clipping occurs if applied gain changes cause output
signal values to fall outside the allowable range. The following graph (Figure 19.10) illustrates
the general effect of increased and decreased gain.
Red Input Value
Red Output Value
A
B
100%
100%
0
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