That point about wilderness is a good one. I've only thought of it in dungeon situations, which is one of the reasons I was thinking low light vision seemed a bit useless without rules about dim light.
I do this, but with this difference: I keep the existing radius, but the first half of the radius is bright, while the second half is dim. If the light source is dim to begin with (like a candle), the outer radius is not lit, effectively halving the lighting radius. For example, a campfire sheds bright light to 50', then dim light between 50' and 100'. A candle sheds dim light to 10' beyond its origin square, and nothing beyond that.Il already extend the radius of bright light, up to the base radius or 5 squares.
So a torch is 5 bright + 5 shadowy for normal vision.
For someone with low-light vision, it is the same as 10 bright.
With this rule, low-light vision do not allow a character to see more further that the others (so no need to describe different things), but it give the lowlight ability some needed help.