Max Klinger, Die Blaue Stunde (1890) The blue hour is the period of twilight at dawn or dusk when the sun is below the horizon. 20-30 minutes right after sunset and right before sunrise, the indirect light takes on a blue shade that is different from the blue of the sky during a clear day. Curious about how we perceive blue while the other colors dim, I did a bit of research into the phenomenon. One site talked about Rayleigh scattering, in which blue light bounces around our atmosphere. The next site said Raleigh scattering is incorrect, and attributed the effect to the ozone. The Atlantic had an interesting theory about how rods and cones in our eyes trade off when light is dim, but the blue cones continue. According to Max Joesch, now of Harvard, and Markus Meister of CalTech, within the retina there are rods and cones. Rods are more sensitive to light, while cones are most sensitive to color: specifically green, red or blue. Signals from the cones are sent to the brain which then translates these messages into the perception of color. As the light dims, the cones don’t work as well and the rods become more active. The rods dampen the output of the red and green cones, much as when we stare at a green field, the receptors for green are dampened and we see red after staring at green. In low light, the rods take over as the other cones become less active, except the blue cone keeps going all on its lonesome. That gives you the impression that you’re seeing blue. (The Atlantic) Calling all doctors and scientists to please chime in! Until then, please enjoy the paintings featuring Blue. Odon Tull, Twilight (1897)Antonio Candida da Cunha, Sunset (1897)Charles W Bartlett, Taj-Mahal, Twilight (1920)Kawase Hasui, Evening at the Lumber Yards Van Gogh, Olive TreesMartha Susan Baker, Twilight No 2 1898Isaak Levitan, TwilightEsther Blaikie MacKinnon, Pulteney Bridge, Bath – TwilightClaude Monet, Poplars on the Bank Picasso’s Blue Period These paintings aren’t about the blue hour, they’re from Picasso’s Blue Period, in which Picasso painted lots of … blue. But notice how he uses the white, yellow, and red. The red and yellow colors are muted into browns, but within the blue environment they still read as red and yellow. Other Blue-ish Nocturny Paintings This collection may feature images that are past the Blue Hour precisely, but notice how the blue is full, and the other colors are muted, giving us the sensation that the light for red and yellow is not just dark, but dim, muted, while the blue is full strength. Susanna Coffey, Sevres Green Foliage From Plot RoadSusanna Coffey, High Moon Toward Mt MansfieldSusanna Coffey, Water YearsCharles Burchfield, Winter Twilight Can you think of a Blue Hour artwork not represented here? Please send it in, or post the artist and title on the website with this post.