I had an annoyance with my MacBook Air, which has taken me quite a while to get sorted. The annoyance was compounded by the fact I had sorted it out on my work MacBook Pro, but didn’t remember how I did that, so wasn’t able to replicate the solution on the MacBook Air.
So, what was the annoyance?
Well it wasn’t huge, simply put, when the MacBook Air is on battery power, when waking from sleep, the MacBook Air screen would be dimmer and I would need to increase the brightness manually.
This didn’t happen with my MacBook Pro, so I knew it was possible, I couldn’t remember what I changed.
I looked at the display system settings on the MacBook Pro and compared it to the MacBook Air, but couldn’t work out what the change I made was.
Then… I was checking the settings in relation to the wake from sleep issue I was having with the MacBook Air when I saw a setting in the battery settings, under options.
Slightly dim the display on battery.

For some reason I had been looking at display options in System Settings and not the battery options.
Fixed that annoyance then.