Atmospheric
Optics
Flying through the Corona
~ or at least, flying very close indeed to the water droplets creating one.
Imaged by Steven Mattan.
"We were flying through very thin clouds on descent into Miami. The colors popped in and out of view. As they say, chance favors the prepared mind … and I had my camera at the ready.
It looked like this with the unaided eye, only fleeting. As the clouds were thin and not contiguous, the colors flashed as we passed through the clouds. The colors were obvious as they flashed in and out. I made a number of images that have no color at all as my reaction time pressing the shutter was too slow. I did not use a polarizing filter"
Image ©Steve Mattan, shown with permission
Birefringence colours from photographing with a polarizing filter through an aircraft window. Image by Martin Izzard.
The corona is produced by diffraction of sunlight by individual water droplets. Waves scattered by the droplet - primarily from its periphery - combine and interfere to produce the ringed pattern.
Colours across photographs taken through aircraft windows can have false colours produced by birefringence in the window layers.
As with any optical effect appearing in a camera, check whether the colours are visible by eye and whether they move about or change when the eye is moved relative to the window.
Other tests are whether the colours disappear sharply where there are clouds or metal parts of the aircraft. These do not polarise light on reflection and do not therefore produce colours.
Check also how the colours are aligned relative to the sun.
In the above image the craft was passing through intermittent thin cloud, ideal for corona or iridescence production by diffraction of sunlight. The many rings and their broad extent speak of very small and uniform (probably freshly formed) water droplets.
