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Medical Forum / General / Vision / June 2009Blue Cone Amplifier
Hi, Our eyes cones only have 2% blue. But how come we can see blue clearly? Where in the brain is the blue amplifier located and how exactly is it amplified? Trish I'm not sure the amplifier exists. For humans, pure blue has to be brighter to match the apparent brightness of red or green. It's why they make 3-D movie glasses out of red and green, not red and blue. -MT > Hi, > [quoted text clipped - 3 lines] > > Trish > I'm not sure the amplifier exists. For humans, pure blue has to be brighter > to match the apparent brightness of red or green. Hmm.. but pure blue is really darker than red or green. But yet we could still see its true shade. As an example. The thermal scanner used in airports to see fever has wavelength of 8-16 micron. Our eyes can't see thermal wavelength (far infrared) because of lack of thermal cones. So we are not supposed to see blue yet we could see it. Trish > It's why they make 3-D movie glasses out of red and green, not red and blue. > [quoted text clipped - 9 lines] > > - Show quoted text - > Hmm.. but pure blue is really darker than red or green. I'm not sure what you mean. Light doesn't have less energy when it's blue. We just don't see it as well. > But yet we could still see its true shade. I'm not sure what that means. "True" would be different for bees and other species, and for humans with color deficiencies. > As an example. The thermal scanner used in airports > to see fever has wavelength of 8-16 micron. Our > eyes can't see thermal wavelength (far infrared) because > of lack of thermal cones. No need for cones because IR doesn't penetrate the cornea. But infrared detectors in your _skin_ can detect fever, light, fire and other sources of warmth. Some snakes use infrared to see and strike in the dark. >So we are not supposed to see blue > yet we could see it. I don't understand. As a rule, everything in the body is there for a reason. We aren't "supposed" to see IR and UV. We did a pretty good job of evolving cones for the range of light that _does_ reach the retina. -MT > Hi, > [quoted text clipped - 3 lines] > > Trish First, "blue" cones make up 8% to 15% of cones, depending on which part of the retina is investigated. http://webvision.umh.es/webvision/photo2.html#densities Second, the "red" and "green" cones can also detect blue wavelengths. http://www.livescience.com/environment/050719_blue_sky.html Judy |
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