Instruction manual

Marlin Technical ManualV.2.7.0
101
Description of the data path
Color correction
Why color correction
The spectral response of a CCD is different of those of an output device or the
human eye. This is the reason for the fact that perfect color reproduction is not
possible. In each Marlin camera there is a factory setting for the color correction
coefficients, see Chapter GretagMacbeth ColorChecker on page 101.
Color correction is needed to eliminate the overlap in the color channels. This
overlap is caused by the fact that:
• Blue light: is seen by the red and green pixels on the CCD
• Red light: is seen by the blue and green pixels on the CCD
• Green light: is seen by the red and blue pixels on the CCD
The color correction matrix subtracts out this overlap.
Color correction in Allied Vision cameras
In Allied Vision cameras the color correction is realized as an additional step in
the process from the sensor data to color output.
Color correction is used to harmonize colors for the human eye. With Marlin
(color) cameras you can use it or switch it off.
Color correction: formula
Color correction is performed on all Marlin color models before YUV conversion
and mapped via a matrix as follows.
GretagMacbeth ColorChecker
Sensor specific coefficients C
xy
are scientifically generated to ensure that Gre-
tagMacbeth™ ColorChecker® colors are displayed with highest color fidelity and
color balance.
Color correction can also be switched off in YUV mode with the help of the fol-
lowing register:
Formula 1: Color correction
Note

Color correction is deactivated in Mono8 mode (RAW image
transport).
red* Crr red Cgr green Cbr blue++=
green* Crg red Cgg green Cbg blue++=
blue* Crb red Cgb green Cbb blue++=