I would like to use a μController to adjust the brightness of VGA/EGA RGB signal. My intention is to allow for a setting from "full brightness" (0% attenuation) to "completely dark/black" (whatever % necessary, probably >80%).
I assume it means that all three channels should be adjusted in parallel to the same level, but I'm also open to them needing their own separate adjustment curves to compensate for the perceived brightness of the different colours. The attenuator/s should be controlled from a (single) μC, like a PIC or similar.
A digipot could be a possible solution, although according to this app note from Maxim (https://www.maximintegrated.com/en/app-notes/index.mvp/id/3081), there seems to be at least -3dB loss for an ordinary digipot at video frequencies. It may be incorrect, or there may be better digipots that I have not found yet.