Light at level 0 on some blocks

I always get a bunch of level 0 light blocks when i'm under any small ceiling,transparent block or not it still persists. It also happens at the foot of Extreme Hills biome mountains. E.G. for the latter would be a block to the top of the mountain that acts as a ceiling for when i am down,it's almost guaranteed the light level will be 0 on a lot of blocks.

I almost forgot to point out: Lava sometimes do not emit the light it should,the entrances of caves often get a instant cut from light level 15 to 0 instantly and torches generated in abandoned Mineshafts almost never emit any light except for the block they occupy.

Knowing the fact i use the options folder in the .minecraft folder to set the overall brightness to -50% and get a realistic lighting experience when it gets dark,a lot these ceiling make it hard to see where i'm going.