Cheetah Pregius Camera with GigE Vision
®
Interface – User Manual
August 27, 2019
Page
104
of
123
Rev 1.0
5.5 Video Amplifier Gain and Offset
Digital gain
Digital gain can be varied from 1x (0 dB) to 4x (12 dB) with a precision of ~0.00097x using the
raw (fine) gain control. There are 3,092 gain steps from 1x gain to 4x gain. Each step increases
the gain by 0.000969932x or 1/1031 from 1024 (1.0x gain) to 4095 (4x gain). Digital Gain does
not provide any improved contrast and should be used cautiously.
To determine the gain step when the gain value is known, use the following steps:
1.
Subtract 1.0 from the desired gain multiplier (e.g. 2.5x gain).
2.
Multiply the result by 1031.
3.
Add 1024.
Or use this formula:
Gain coefficient = [[Desired gain – 1] *1031] +1024.
If the desired gain is in dB, use the following formula:
Gain coefficient = [[[anti-log
10
(Desired gain (dB)/20)]-1]*1031]+1024.
EXAMPLES:
1) Desired gain is 2.5x: [(2.5 – 1.0)*1031]+1024 = 2570.
Set coefficient to 2570.
2) Desired gain is 6 dB, then the code is 2050.
Minimum setting is 1024 corresponding to 1x gain. Below are other examples:
Gain (dB)
Multiplier
Coefficient
0 dB
1x
1024
3 dB
1.41254x
1449
6 dB
1.99526x
2050
12 dB
3.98107x
4097
Digital Offset
Digital offset is a digital count added or subtracted from each pixel. The range is - 512 to
+511 counts.
Black Level Auto-calibration and Offset
The camera automatically adjusts black level based on measurements of the dark reference
lines at the start of each frame. Imperx recommends leaving the BlackLevelAuto engaged
(continuous). If auto-calibration is disabled, you can set the BlackLevel and adjust it from 0 to
255 counts. Black level will vary with temperature and gain settings
