At birth. They may not know what they see then, but they will react to light, and by 1-2 months should focus on your face. When they answer your smile with theirs, then you'll know for sure!
At birth. Babies are able to see immediately and as early as 7 months gestation. They like light/dark contrast at birth and faces. By 3 months, color vision is improving and they see faces so well that they can prefer parent faces to others and light up in response to a good smile. Depth perception vision is not great until 3-5 months.