A physicist duh moment.
Oct. 27th, 2009 09:59 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
dianavilliers
A rainbow is produced by total internal reflection of sunlight inside raindrops. Which means that it will be polarised. Which means that with appropriate filtering I should be able improve the contrast somewhat...
The direction of the polarisation will be along the bands, so a polarising filter will only enhance the parts of the arc that are in line with the filter. If the filter is vertical, the sides of the rainbow will be bright and the top will disappear. Twist the filter 90 degrees, and the top will brighten while the sides fade. I only rarely see full arcs anyway, and don't have a wide enough angle lens to capture them if I did, so this isn't a huge limitation. The filter does good things for the foreground clouds too.
So here we have what I think is is my first successful capture of a double rainbow. The secondary is not very bright, but it is there!