Iridescence Above Bedford, Ohio

August 19, 2010


Photographer: Ken Andrews 
Summary Author: Ken Andrews

These shimmering altocumulus clouds appeared above an approaching storm near Bedford, Ohio, late in the day on July 23, 2010. Iridescence nearly always occurs in mid-level altostratus or altocumulus clouds (between 5,000 ft and 15,000 ft or 1,524 - 4,572 m in altitude). Such clouds are made up of tiny water droplets which, because of their minute size, deflect sunlight rather than refract or reflect it. When a wave, in this case waves of light, encounters an obstacle such as a small droplet of water it's bent and spread out in such a way to produce overlapping colors -- the process of diffraction. The brightest and purest colors result when the droplets are of the same size throughout the cloud.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX120 IS; Focal Length: 28.1mm; Aperture: f/4.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No; Orientation: Rotate 90; Color Space: sRGB