They see better in the dark than we do, but not with the definition we do. They see movement far better than we do and normally a deer needs more than just a visual to actually spook, they need movement and the ability to make out your outline. The one sense that they will spook on all by itself is smell, if they smell you they are GONE!!!

I have on a few occasions when the wind is right been standing in the wide open and through staying perfectly still when they are looking right at me and moving slowly when they are not, been able to get extremely close to them, within 20 foot, talk about exhilirating!