Light: A spell to cast light in a circle 3" in diameter, not equal to full daylight. It lasts for a number of turns equal to 6 + the number of levels of the user; thus, a 7th level Magic-User would cast the spell for 13 turns.This is another spell with no range listed, at least in this version. We could go with the 10 feet/spell level without any problem. This is the first spell listed that includes the Magic-User's level as a variable; in this case, it alters the duration. If the duration is meant to be exploration turns, it lasts longer than a torch and is essentially a replacement. If the duration is in combat turns, then the Light spell is an emergency light source, not a replacement for torches.
It's also the first spell that affects an area; Protection from Evil creates a "circle" around the caster, but this is purely conceptual, since the spell only affects one person of any size. It would be nice to regularize areas across all spells the same way I'm considering regularizing ranges, but if we use 10 feet diameter per spell level, the Light spell becomes much smaller; if we use 10 feet radius instead of diameter, that could cause problems later. Perhaps 30 feet diameter per 3 spell levels, round up. We'll see how this affects other spells as we go along.
The big question is mobility. Perhaps this is reading too much into the wording of the spell, but I think it's notable that it "casts light in a circle" rather than "causes an object to radiate light in a circle". I think this is meant to be a non-mobile effect, effectively lighting a specific room, rather than replacing a torch.
The brightness is specified as "not equal to full daylight". This is important mainly because the monsters listed as sensitive to light are only affected by full daylight. There may be more sensitive creatures at the GM's option, of course, but in general, a Light spell isn't that effective as an attack. Casting Light on a creature's eyes should only startle it briefly (reroll surprise,) but might trigger a morale roll for goblins and kobolds.