Patrice Touhar took this photograph through the window of an airplane using a polarization filter and so made these polarization colours appear.
The colours are generated by the combination of three circumstances:
1. There is polarized light behind the window
2. The window is made of a double refracting matter
3. A polarization filter is used in front of the window
Under these circumstances, the light gets split up into two coherences of polarized components which travel through the window at different speeds. This causes a phase difference the amount of which depends from the wavelength. This means that the polarization gets transformed once into a linear polarization of a different direction than the origin for a certain colour, and into a circular polarization for another colour (Lissagiu interference of two waves). As the polarization is now dependent from the colour, the colours appear when a polarization filter is used, no matter if this filter is placed in front of the eye or in front of a camera.
These colours can be seen and photographed under the following circumstances:
1. There is polarized on one side of the window coming from the blue sky (Rayleigh scattering) and reflection from water and the scattering caused by clouds
2. The window is made of plastic. In this material there are mechanical tensions which cause a double refraction.
3. There is a polarization filter in front of the camera.
The last condition is not necessary if you look at the window from an acute angle. Then the light becomes already polarized by the refraction. In this case there is no filter necessary to see the colours. However, the colours you can see under this circumstance are fainter than the colours seen through the polarization filter because refraction polarizes only a part of the light.
You can also find another observation of this kind in this former thread.
At the beginning of this winter season at a cold morning – dark outside – with a thin layer of hoarfrost on the inner side of the bus windows I’ve noticed that the light of the street lamps’ light was not simply scattered on the windows, but having colorful corona around them. At that time I had no camera with me… All along the winter I was waiting for the same display each morning when some ice was on the bus windows, but for long weeks I haven’t met with such spectacular phenomena again.This day was my day on 24th January. Very thin layer of frost was on the inner part of the windows, (with some frost ferns too by the corner of the window frame), mainly this layer was made of small uniform ice crystals made of frozen vapor droplets, we might call it an ice film, it was about 0,1 mm thin.All the lamps outside had a corona, no matter how far the lamp was.The street lamps with white light had the most beautiful color range, the orange colored light of sodium vapor lamps had a less distinct colors and they were a bit moved towards the reds. Not only the street lamps’ corona was seen on the ice layer, but a much less spectacular corona around the reflection of the inner lamps of the bus too! At the part of the frost ferns pattern the corona became irregular in shape. When the lamp was near the window I could also see the bigger outer rings of the corona. Almost the same phenomena appears when simple water vapour is on the windows, but that one is really less poor in colors compared to the ice film corona.This was the first time when I could take photos of a corona produced by ice crystals. It’s a pity, I could not take close-up photo of the ice layer itself (the bus was driving me to work so it was permanently moving).
Photos are collected here: The only afterwork was some noise reduction and size reduction. It was totally dark outside, so the pics were taken with ISO200 – ISO400; aperture F4 – F5,6; exp. 1/15 – 1/25 sec. auto white balance; without tripod or any kind of help to avoid moving.I wonder if the same phenomena would appear if the outer side of the windows would have a layer of hoarfrost on it. It’s only weather’s turn to show it up!
Author: Monika Landy-Gyebnar, Veszprem, Hungary
While flying from Izmir to Ankara in Turkey on monday the 2nd of April 2007 at 10.15am Selen Ediger wanted to take an aerial shot of the mountains below with my canon ef 10-22mm lens and Hoya multi coated polarizing filter. With naked eye the colors were not visible but when she looked through the camera she saw that the land and the sky was covered with rainbow colors. The contrast and the saturation are adjusted a bit.
What’s the origin of this colours?