LEARNED IT · 08/26
This camera has no gain control at all
Exposure time is the only brightness lever the SV205 exposes. Don't go looking for a gain slider.
The full v4l2 control list has no gain under any name. Not hidden, not differently labelled — absent.
The only lever is exposure_time_absolute: units of 100 µs, range 1–10000, so
0.1 ms to 1 s.
Worth knowing up front because every planetary imaging guide assumes a gain/exposure pair and talks about balancing them. Here there is one knob.