In case it might be of interest, here's the text from my LS-30 Nikonscan manual
Analog gain is used to adjust the intensity of the scanner‘s light
source, emphasizing selected colors in the input image. The
controls for analog gain consist of four sliders: a master slider
that allows the user to increase the brightness of all LEDs in the
scanner’s light source simultaneously, and red, green, and blue
sliders that allow independent adjustment of the red, green, and
Moving a slider to the right increases the intensity of the affected
LED; moving it to the left decreases the intensity. Click
the Help button for information on using analog gain.
Note: Setting the intensity of the scanner’s light source too high
may produce “smear” or other defects in the scanned image.