Does decreasing light radius decrease how far monsters can see you? I seem to remember something about a -13 light radius made you "invisable" to monsters, (not that your equipment would be that great.) Is a -13 light radius even possible.
Though the information is probably valid, I think there was some miscommunication there.
If you have no items affecting it, your base light radius is 13. Hence, in theory, items adding up to -13 to light radius would reduce it to zero. I have no reason to disbelieve Amberwave's assertion that a radius of 4 (or -9 from items) is the smallest it can actually get.
I've also read many places that 18 (+5 from items) is the highest your light radius can go.
What surprises me is the assertion that your light radius has any effect on monsters noticing you. I'm willing to believe it (and this is the second time I've heard this idea), but I always thought of increased light radius only as a way to see the mosters coming better in dark places. Kind of annoying if such a nice-sounding enchantment simply made the ...ahem... "condemned" skeletal archers shoot you from even farther away.
Back in the days of the first Diablo there used to be a build called an "assassin". Basically the idea of it was to get ur light radius down to 0, at this point monsters wouldnt see you and thus wouldnt attack you. You then used scrolls of infravison to let you see them and pick them off at your leisure. Basically this build worked much the same way as the current Necromancer skill Dim Vision, which essentially lowers your light radius, decreasing the range at which monsters will see and attack you.
I dont know whether this build is still viable since i havent tried it personally and everyone else is too busy spamming hammers, or teleporting around with their enigma armours to try it.
Anyway, It used to be possible not sure now. Might be worth trying if you want to take the time, i cant see why it wouldnt work, much like maxed dim vision so successfully employed on Mongojerry's pacifict necromancer.