I was just watching a whole discussion that Dan “Delta” Collins and Paul Siegel were having on their Wandering DMs YouTube channel all about Infravision, and just when I was going to leave a comment about how I would rule it, they came to my preferred solution: treat it like thermal imaging.
Basically, if you’re going back to the beginning when Elves and Dwarves had “infravision” and not “dark vision” or “low light” vision, the question is what exactly can they see, and how far. Can they see details? Colors? Is the ability washed out by torches? The LBBs are actually silent on the whole matter, while Chainmail says Dwarves and Elves “can see in normal darkness as if it were light”. Interestingly, so can Wizards (in OD&D that must be the purpose of the Infravision spell). Greyhawk specifies that Dwarves can see monsters up to 60′ away in the dark.
I’m not 100% sure of how we ran it back in the day, when we didn’t even have Chainmail but did get Greyhawk shortly after it showed up in the local game store. As best as I can recall, though, we took the “see monsters” and “infravision” description pretty seriously, treating it as the ability to see heat. That meant no ability to discern anything that wasn’t hot: no stone walls, doors, statues, traps… if it wasn’t warmer than the surroundings it just wasn’t visible without a light source.
Interestingly, I don’t think we arrived at that because of concerns of the distances lanterns and torches worked vs. the 60′ for infravision, because we mostly didn’t track light sources and the like. It was too finicky for us, we just wanted to kick down doors and kill monsters and take their stuff. Maybe there was an occasional trap or something that dunked you in water and doused your torch, but I just don’t recall much if any discussion of how far down a corridor you could see…but I do recall discussions of things like whether zombies were room temperature or not.
The only thing I think I would do differently now is I’d probably let Dwarves and Elves operate in “ordinary darkness”, that is to say outdoors at night, as if it were daylight as per the Chainmail rules. It’s only in dungeons and caverns where you have near total darkness,with barely a stray photon, that I’d be more strict about the limits of infravision. And I think that Paul has a good point in the video, that you don’t want characters able to see up to 60′ in a dungeon with perfect clarity: most published dungeon maps are drawn to a scale where seeing that far spoils all the surprise about what’s down at the end of the corridor, or lurking in the far side of a big room. On the other hand, being able to see if there’s a living creature down there, but nothing about its surrounding or maybe even what it is… that’s giving the players options while keeping things still a bit spooky and mysterious.
Having infravision washed out by nearby heat sources like torches, as in later editions of D&D, strikes me as more trouble than it’s worth, particularly if you’re limiting it to only what infravision as thermal imaging would show.
One bit that I don’t recall seeing much online discussion of, and that Dan and Paul didn’t touch on, is that it’s clear from Book III of the LBB that “Monsters are assumed to have permanent infravision as long as they are not serving some character.” I recall somebody somewhere pointing to that as evidence of the “Mythic Underworld” nature of dungeons, and I may run with that for my End Times campaign. Or I may forget about it as just another thing that’s too fiddly to worry about.