I am running YellowDog 2.3 on a G4-upgraded 8500, with an Apple 17"
ColorSync monitor. I have XF864 (as it came) running very nicely at
1024x768, but every time I try it at a lower resolution the screen seems
very dark. I have trawled group and web archives as much as I can
without seeing anything like this as a problem.
Does anyone know why 800x600 or 640x480 should be so much darker than
1024x768? I see the effect at 16bit and at 8 bit colour. I have tried
messing around with the gamma control, but it doesn't improve things
very much. It may be the whole frame buffer (not just XF86), because
MacOnLinux, running in console mode, gives the same effect (i.e.
1024x768 looks v.nice, 800x600 looks darker, and so on. In fact here, if
I use the MacOS software to change resolution in MacOnLinux, I also see
the same effect).

all help/advice appreciated,