Logarithmic Gain Adjustment

This gain control scheme allows establishing one of seven gain steps logarithmically distributed.

Simply set the GainCtl parameter to one of the seven values tabulated below, and maintain all involved GainTrim1,GainTrim2 and GainTrim3 parameters to zero.


GainCtl value	Gain for all camera channels
GainCtl value	Logarithmic expression	Linear expression
+3 dB	Nominal gain + 3dB	Nominal gain x 1.413
+2 dB	Nominal gain +2dB	Nominal gain x 1.259
+1 dB	Nominal gain +1dB	Nominal gain x 1.122
0 dB	Nominal gain	Nominal gain
-1 dB	Nominal gain -1dB	Nominal gain x 0.891
-2 dB	Nominal gain -2dB	Nominal gain x 0.794
-3 dB	Nominal gain - 3dB	Nominal gain x 0.708

When these values are used for GainCtl, the Gain parameter is not applicable.

Once the common gain is chosen for all camera taps (1, 2 or 3), it is still possible to trim an individual tap through the GainTrim1, GainTrim2 and GainTrim3 parameter.s

The control resolution for GainTrim1, GainTrim2 and GainTrim3 is not specified. Each unit increment or decrement correspond to the minimal amount of gain alteration the board hardware is supporting.

Setting the GainTrim1, GainTrim2 and GainTrim3 parameters to a positive value increases the gain for the relevant camera tap above the value established by the GainCtl common parameter. The correction induced by GainTrim1, GainTrim2 and GainTrim3 is simply added to the common gain after the logarithmic conversion of Gain.

Setting the GainTrim1, GainTrim2 and GainTrim3 parameters to a negative value decreases the gain for the relevant camera tap below the value established by the GainCtl common parameter.

The minimal and maximal values for GainTrim1, GainTrim2 and GainTrim3 depend on the value assigned to GainCtl. The limits are in the order of magnitude of ±500.