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.

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.

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.