Lower values of the brightness cannot be reached with hardware buttons on the keyboard.
The use case is in the morning when starting my computer I want to go in the lwoer values to not hurt my eyes. I usually go tho 1% or even below.
Also the increment og the hardware key is 5%. So I have to go in the power preference and slide with the tiny slider below 1%.
Then as the sun goes up I have to go to 1,5% 10 min after and so one.
Proposed Solution 1:
Have a simple adaptative scale :
- from 0 to 5% an increment of 0,5% (or 1%).
- from 5% to 100% the actual behaviour of 5% increase
This wasn t such an important problem on my previous laptop that reached
- 250 nits = lowest value 12 nits
- my new laptop reaches 450 nits = lowest value 22 nits
My eyes will be greatfull 
PS: For Auto birghtness : I have set a feature request on the github issue