condition mean min max 4 h after light 3.3 3.3 3.3 8 h after light 2.45 2.0 2.9 12 h after light 2.0 2.0 2.0 4 h after dark 2.35 2.1 2.6 8 h after dark 2.5 1.9 3.1 12 h after dark 2.3 2.2 2.4