yeah, the "brightness" slider in the options menu controls the "gamma" cvar. "gamma 1" is when the slider is all the way to the left; the darkest setting. 

If it is I'd like to submit a bug report for having the wrong name. Gamma is not brightness.

That's just terminology, but unfortunately it's terminology that dates back to the original software Quake, so it's probably too late to change it now.

Change the menu text from "brightness" to "gamma" and you'll get complaints that there is no longer a gamma option.

Change the cvar name and behaviour and you get complaints from the other perspective.

Accept it as a quirk of Quake and - of course - the name in the menu is all wrong, but given 20 years of legacy it's probably the least invasive option.

Similarly, what certain engines call "contrast" isn't actually contrast at all either. 

Whatabaout a test map/mod to set the lighting right so as to standardise things a bit ?
A la adjust your slider until you barely see X etc but in a purpouse built map with prompts ? 

That’s not such a bad idea 

By the way, the darkest shades of darkness in the software renderer are darker than in the hardware renderers. The software renderer clamps the last non-black level of darkness to full black, and some colors in the palette goes black before others.

I'd highly recommend testing the maps in the Mark V WinQuake engine, as AFAIK it's the software-rendered engine that's most faithful to vanilla Quake while also supporting most extended limits. 

So, lets do it :D

A map with a set of rooms and prompts to help adjust ones settings to something sane and close enough to what everyone else is using

Like "adjust your whatever until you faintly see the zombie on the wall at the end of the room" etc..

This would be the most flexible approach to a "standardization" of brightness/darkness settings. If everyone designs with similar settings.

Seems to the only way that could work across different engines/sourceports etc. 

I'm pretty sure that won't work across different monitors and lighting scenarios as ericw and others have alluded to. Since your monitor could be darker or lighter than mine you will get different results no matter what.

If you use the start map as a reference when you are lighting levels you should be okay. However, don't do what I did last time and rely on screenshots. You need to "eyeball" it "live" in-game. 

This could be used just to get the display in the ballpark. 

If i raise the brightness to the maximum while on a pitch dark room i begin to guess something, but i use a CRT here. Is there so much of a difference with TFT one? 

I don't see any symbol on my S7 screen at max brightness? The dang text hurt my eyes tho.