Comment 19 for bug 1351833

I've also noticed this situation. But I think it's not really a bug but a confused change made in power settings.

@sayantan13 can you check if you can also see the same results:

Steps to verify:

1. check "Dim screen to save power"

2. in "Turn screen off when inactive for", select "2 minutes"

And then wait for the system goes to inactive, you should see result with follow progress:

normal -> system goes inactive (0s) -> screen dim at 30% backlight (1:30s) -> screen starting dimming again (1:50s) until black/off.

If you cannot see it dimming but it still goes to black screen, not could possibility your backlight does not work at first place.