Disable lock screen dimming in 16.04
Solution 1:
Ubuntu 16.04
I have also been trying to figure out how to stop the lock screen from dimming. I can not seem to find anything associated with the screen dimming when going to the lock screen that I can edit/tweak.
I tried all the usual suggestions of
gsettings set org.gnome.desktop.screensaver idle-activation-enabled false
gsettings set org.gnome.desktop.session idle-delay 0
gsettings set org.gnome.settings-daemon.plugins.power idle-dim false
but none of them worked.
**** WORKAROUND ****
However invoking an activity once the dimming starts seems to then follow what ever settings you have enabled in the system settings > Brightness & Lock > settings.
The way you can stop it is by locking the screen then typing a few random characters into the password prompt. It will now no longer dim.
It's not a perfect solution by a long shot as the user has to invoke the lock screen manually to get it to work but it may help.