Low-Light Vision - Why?
So I'm an Elf. One of my friends is Human, and the other is a Dwarf.
We enter a cave room. It is pitch black. I cast my Light-cantrip.
So now we have light 20 feet into the cave, and dim-light for another 20.
The Dwarf doesn't care much. He can see 60' in total darkness, so unless we run into some nicely coloured paintings he doesn't need any light at all.
The human can see 40'. Okay, the last 20 is dim-lighted to him, but...? What does that matter? Where is the rule that makes this a problem? Does he suffer disadvantage on search and perception checks? Do targets have concealment? I can't find the rules.