Nvidia drivers screen brightness and back light

[Scott Bennett]

Ken Moore <ken at ixsystems.com> wrote:

> xbrightness and redshift do not touch the LCD levels within your monitor at 
> all - they both do software-level brightness control through modifying the 
> X server settings for colors and such (which is why they trample all over 

     Hmmm...  I've just tried it and looked closely and, yes, xbrightness
does appear to leave the backlighting on with "xbrightness 0".  I hadn't
noticed it worked that way on this monitor.  However, the monitor I was using
until around three weeks ago is an ancient beast that doesn't use LEDs for
backlighting and doesn't understand EDID.  On that monitor, xbrightness
definitely turned the lighting level up and down.  If I set it to 0, it was
utterly black, not like the LED-backlit screen I'm using now.
     xscreensaver's method was to "blank" the screen at that timeout or to
change its state to standby and off at those timeouts.  Blanking the screen
did not appear to affect the lighting level.  I can't test it on the monitor
I'm now using, thanks to the bug I already reported.
     Anyway, my apologies to all concerned if I missed the point or gave
wrong information in my earlier postings.

> each other if you try to run both). If you want hardware-level brightness 
> control there are a couple options:
>
> "xbacklight" is a utility similar to xbrightness, but only does 
> acpi/hardware brightness. It only works on monitors which support the ACPI 
> power levels and such though, so it might not work for you. 

     I had forgotten all about that one.  Thanks for that!  I've just installed
it and will try it on this monitor shortly.
>
> You can tweak the sysctl on your system to turn down the monitor brightnees 
> directly (if supported by your monitor - most laptops are supported but 
> desktop monitors are hit-or-hiss).
> `sysctl hw. | grep brightness` should show you which one(s) are available 
> on your system.
>
> "pc-sysconfig" is a tool on PC-BSD/TrueOS systems which is a front-end to 
> the sysctl method for controlling screen brightness (as well as a few other 
> things like putting your system into suspend mode), and allows the user 
> make the changes as needed (sysctls can usually only be changed by root). 
> Run "pc-sysconfig -h" to see the options for reading/changing the screen 
> brightness levels as you need.
>
     I think I'll pass on that one if it does things as unpleasantly as, e.g.,
life-preserver.  Using sysctl directly sounds like a reasonable alternative
where xbacklight isn't available.  Thanks for pointing that out.  I had seen
it before, but never knew whether it was settable after boot.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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