Breck this morning....
- Thread starter MIke R
- Start date
Petri
Senior Insider
Rich and Sue
SBH Insider
Ahh, but define blue. The digital camera detector is more sensitive to blue than other colors, so I am told. Just look at the bluish tint of the snow on the rooftops in Breck(can "fix" that in photoshop). The spectrophotometer, I suspect, has a rather flat response and I think the eye is more responsive to yellow (sunlight). The Spectrophotometer may be the best judge of particulates in the air, but beauty is in the eye of the beholder, eh?
Petri
Senior Insider
So true..
I could understand that South Africa, Fiji, New Zealand or Uluru in Australia have blue sky as they are quite remote parts of the world. We could most definitely feel the difference in Eastern Island. Or perhaps it was just the lack of ozone layer burning a hole to our forehead..
We also had spectacular sky in the Antarctica (contrast with the white snow?) and here in Finland summer sky feels much more blue than in central Europe (latitude?). I'm not sure about the altitude; the sky feels blue in the US and the Alps but one didn't get the same feeling in the Anders nor Himalayas (both were summertime, though). Perhaps it's more about the contrast of colours as our spring days with snow and clear sky feel pretty special, too?
http://www.patarnott.com/atms749/pdf/blueSkyHumanResponse.pdf
"Human color vision and the unsaturated blue color of the daytime sky"
http://en.wikipedia.org/wiki/Diffuse_sky_radiation
The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun.
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/General/BlueSky/blue_sky.html
When we look up at the sky, the red cones respond to the small amount of scattered red light, but also less strongly to orange and yellow wavelengths. The green cones respond to yellow and the more strongly scattered green and green-blue wavelengths. The blue cones are stimulated by colours near blue wavelengths, which are very strongly scattered. If there were no indigo and violet in the spectrum, the sky would appear blue with a slight green tinge. However, the most strongly scattered indigo and violet wavelengths stimulate the red cones slightly as well as the blue, which is why these colours appear blue with an added red tinge. The net effect is that the red and green cones are stimulated about equally by the light from the sky, while the blue is stimulated more strongly. This combination accounts for the pale sky blue colour. It may not be a coincidence that our vision is adjusted to see the sky as a pure hue. We have evolved to fit in with our environment; and the ability to separate natural colours most clearly is probably a survival advantage.
Here's pretty good description of the camera sensors, http://www.cambridgeincolour.com/tutorials/camera-sensors.htm
which have twice the amount of green sensors than blue or red.
I've always thought about putting a simple digital camera to photograph the sky every 15 minutes and calculate a "blue-index" for the day and place.
I could understand that South Africa, Fiji, New Zealand or Uluru in Australia have blue sky as they are quite remote parts of the world. We could most definitely feel the difference in Eastern Island. Or perhaps it was just the lack of ozone layer burning a hole to our forehead..
We also had spectacular sky in the Antarctica (contrast with the white snow?) and here in Finland summer sky feels much more blue than in central Europe (latitude?). I'm not sure about the altitude; the sky feels blue in the US and the Alps but one didn't get the same feeling in the Anders nor Himalayas (both were summertime, though). Perhaps it's more about the contrast of colours as our spring days with snow and clear sky feel pretty special, too?
http://www.patarnott.com/atms749/pdf/blueSkyHumanResponse.pdf
"Human color vision and the unsaturated blue color of the daytime sky"
http://en.wikipedia.org/wiki/Diffuse_sky_radiation
The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun.
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/General/BlueSky/blue_sky.html
When we look up at the sky, the red cones respond to the small amount of scattered red light, but also less strongly to orange and yellow wavelengths. The green cones respond to yellow and the more strongly scattered green and green-blue wavelengths. The blue cones are stimulated by colours near blue wavelengths, which are very strongly scattered. If there were no indigo and violet in the spectrum, the sky would appear blue with a slight green tinge. However, the most strongly scattered indigo and violet wavelengths stimulate the red cones slightly as well as the blue, which is why these colours appear blue with an added red tinge. The net effect is that the red and green cones are stimulated about equally by the light from the sky, while the blue is stimulated more strongly. This combination accounts for the pale sky blue colour. It may not be a coincidence that our vision is adjusted to see the sky as a pure hue. We have evolved to fit in with our environment; and the ability to separate natural colours most clearly is probably a survival advantage.
Here's pretty good description of the camera sensors, http://www.cambridgeincolour.com/tutorials/camera-sensors.htm
which have twice the amount of green sensors than blue or red.
I've always thought about putting a simple digital camera to photograph the sky every 15 minutes and calculate a "blue-index" for the day and place.
