Thursday, December 25, 2014

Iridescent clouds and crazy contrails

December 24 had some interesting clouds that produced great iridescence. My hand is blocking the sun in the picture below.

Iridescent clouds, 24 December 2014, ~12:00

The color in these photos matches that perceptible to the eye, though the sky is darker in my photos due to my camera's adapting to the brightness. Our eye can detect the colors of the sky and iridescence, but the camera, at least mine, has to choose one. If I had taken identical photos using different exposure times, I could combine the the images in Photoshop to reproduce the full range of color; but the iridescence was fleeting, leaving no time for tripod mounting or controlled exposures. My best results came from using the camera's automatic landscape settings.

Minutes after the above photos, a jet passed through the cloud, leaving a contrail up to the cloud but erasing the where it flew through. The erased parts are probably the hole-punch effect, where a plane or strong updraft punches holes in a cloud. This tells me that the cloud was very thin, perhaps a requirement for producing the iridescence. As the clouds thickened in the afternoon, the iridescence was gone.

Condensation trail with hole punch effect


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