UngeheuerLich
Legend
I think I want an even trade. Where "brightvision" is blind in darkness, darkvision is blind in brightness. Races are either on oneside or the other. Dimness is a kind of neutral territory, but darkvision has an edge.
Brightvision (Normal Human)
Bright: color
Dim: shades of gray
Dark: Blind
Darkvision
Bright: blind
Dim: color
Dark: shades of gray
I am missing a category: near total darkness. Where someone woth brightvision can see enough to navigate (stary night), but not necessarily enough to discern a foe.
Also I would allow someone with darkvision to be able to navigate on a cloudy day or in some shades.
I also might have creatures that are able to switch their form of sight or at least allow to see normally in dim light/bright light with a few minutes of adaption.