Q:

Is there an easy way to calculate a block's light level?

I'm trying to build a house out of ice, for no other reason than sheer novelty. (Though perhaps also because I want to use my Silktouch I pickaxe)
Ice is a very finicky building material, prone to melting when exposed to the "normal" light levels of a torch. Specifically, if any adjacent block attains a light level of 12 from anything other than direct sunlight, it will melt.
And so, I reach a conundrum. I want to light my house enough so that I can see while walking through it, and also enough to completely prevent mobs from spawning inside my house. This means I want to keep the light level approximately between 8 and 11: easy enough to do someplaces, but a pain in the butt to calculate for every potential spawnable square.
Is there some way to identify the light level of a block without the tediousness of manually calculating each block's light level? I'd prefer an external tool over a mod, but I'm willing to consider the latter anyway.

A:

Your best bet would be to open up your favorite skin, find the lighting file -- like this one -- and modify it in your favorite image editor so that the lighting levels above/below/inside your desired range are made obvious (red, green, and white may be good choices). Be sure to disable smooth lighting while you do this, though.

A:

Press F3, and look for the area labeled bl: When you find this it will tell you the artificial (not natural) light of the block you're standing on.

A:

Use the What's My Light Level? mod, compatible up to 1.9 pre-4 (unstable) and 1.8.1 (stable).
This mod provides an overlay that shows the light level of the block you are standing on.

