Scotopic Vision: Seeing in Near-Darkness

This simulation renders a dark Halloween scene under adjustable ambient light and shows how human night vision actually works. As you lower the light-level slider the view shifts from full-color cone (photopic) vision toward desaturated, blue-green-tinted rod (scotopic) vision — the Purkinje shift in action, where warm colors like the pumpkin's orange sink toward black faster than cool ones. Trigger a bright flash to bleach rhodopsin and watch a real countdown as rod sensitivity regenerates through the classic biphasic dark-adaptation curve. The inset diagram shows why: cone density peaks sharply in the fovea while rods, absent from that same center, dominate the periphery — the reason faint objects are easier to see with averted vision than by staring straight at them.