Sunday, August 12, 2007

Purple sun?

These pictures were taken on a flight from Geneva to Warsaw on 18 July 2007. Shortly, after the sun disappeared behind a bank of clouds, I was surprised to notice that the LCD display of my Lumix TZ-1 camera was showing a purple sun. As purple is not a colour not normally associated with the sun, my first thought was that my camera had been damaged by taking pictures of the sunset. However, it soon became clear that the camera really could "see" the sun - despite the fact that the sun was completely invisible to my eyes! In fact, the sun remained visible to the camera for about 2 minutes after it disappeared according to my eyes.
Notice that the sun appears to have been squashed vertically (due to atmospheric refraction).
The explanation for this phenomenon is that the CCD sensors used in digital cameras have their peak sensitivity in the infra-red - typically at a wavelength of about 1000 nm, which is well beyond visible spectrum of 400 - 700 nm. You can test the infra-red performance of your own digital camera by pointing a TV remote control at the lens of the camera from a distance of about 15 cm (6 inches). Most remote controls transmit infra-red at wavelengths of 850 - 1000 nm. Your camera viewfinder will probably show a purple light when you press a button on the remote control. The purple colour suggests that the red and blue sensors in the camera are sensitive to infra-red - but not the green sensor. Hence, the purple sun .....

3 comments:

Anonymous said...

Ive seen a purple sun before with just my eyes and when I took the picture It looked the same as what I saw. And it was visible for quite a while. When we could no longer see the sun it was just barely visible on the camera. The day I took it it was foggy out and their might have been smoke mixed in but I don't know.

Heres a link to the picture I took of it.

http://copperarabian.deviantart.com/art/Purple-sunset-91471252

generic viagra said...

wow i never see something like this in my all life, but it's should be amazing.
thanks for sharing.

generic viagra said...

This is really amazing. Have never seen such amazing part of sun. Great and thanks for sharing.