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#ActualHodgman

Posted 20 November 2012 - 08:11 PM

We have 3 kinds of "colour receptors" (cones), excluding mutations, and 1 kind of "night vision receptor" (rods).
In daylight, the rods aren't functional, so we have normal colour (photopic) vision, the optic nerve carries 3D colour to the brain. In this mode, you're actually the most sensitive to green colours -- when shown equally reflective red/green/blue surfaces, the green ones will appear to be the brightest.
e.g. when calculating the brightness of an RGB colour, weighted formula like "0.3*R + 0.59*G + 0.11*B" are often used to reproduce the sensitivity of our cones to each wavelength. Many games use such formulas in their tonemappers, but these are only valid for daytime lighting conditions. They're completely wrong for low-light.

In complete darkness, the cones aren't functional, so we have grainy colour-less (scotopic) vision. The optic nerve basically carries 1D colour to the brain.

In low light, the rods begin to contribute information at the same time that the cones are, which is called mesopic vision. There's 4 sensors picking up light in this mode (3 cone types + 1 rod type), but the optic nerve still only carries 3D colour information, so we still have trichromatic vision. However, because the wavelength that's absorbed by the rods is a "blueish" colour, this causes what's called the "Purkinje shift", where your eyes are now more sensitive to blue wavelengths, making them seem brighter.

#2Hodgman

Posted 20 November 2012 - 07:55 PM

We have 3 kinds of "colour receptors" (cones), excluding mutations, and 1 kind of "night vision receptor" (rods).
In daylight, the rods aren't functional, so we have normal colour (photopic) vision, the optic nerve carries 3D colour to the brain. In this mode, you're actually the most sensitive to green colours -- when shown equally reflective red/green/blue surfaces, the green ones will appear to be the brightest.
e.g. when calculating the brightness of an RGB colour, weighted formula like "0.3*R + 0.59*G + 0.11*B" are often used to reproduce the sensitivity of our cones to each wavelength. Many games use such formulas in their tonemappers, but these are only valid for daytime lighting conditions. They're completely wrong for low-light.

In complete darkness, the cones aren't functional, so we have grainy colour-less (scotopic) vision. The optic nerve basically carries 1D colour to the brain.

In low light, the rods begin to contribute information at the same time that the cones are, which is called mesopic vision. There's 4 sensors picking up light in this mode (3 cone types + 1 rod type), but the optic nerve still only carries 3D colour information, so we still have trichromatic vision. However, because the wavelength that's absorbed by the rods is a "blueish" colour, this causes what's called the "Purkinje shift", where your eyes are now more sensitive to blue colours, making them seem brighter.

#1Hodgman

Posted 20 November 2012 - 07:54 PM

We have 3 kinds of "colour receptors" (cones), excluding mutations, and 1 kind of "black and white receptor" (rods).
In daylight, the rods aren't functional, so we have normal colour (photopic) vision, the optic nerve carries 3D colour to the brain. In this mode, you're actually the most sensitive to green colours -- when shown equally reflective red/green/blue surfaces, the green ones will appear to be the brightest.
e.g. when calculating the brightness of an RGB colour, weighted formula like "0.3*R + 0.59*G + 0.11*B" are often used to reproduce the sensitivity of our cones to each wavelength. Many games use such formulas in their tonemappers, but these are only valid for daytime lighting conditions. They're completely wrong for low-light.

In complete darkness, the cones aren't functional, so we have grainy colour-less (scotopic) vision. The optic nerve basically carries 1D colour to the brain.

In low light, the rods begin to contribute information at the same time that the cones are, which is called mesopic vision. There's 4 sensors picking up light in this mode (3 cone types + 1 rod type), but the optic nerve still only carries 3D colour information, so we still have trichromatic vision. However, because the wavelength that's absorbed by the rods is a "blueish" colour, this causes what's called the "Purkinje shift", where your eyes are now more sensitive to blue colours, making them seem brighter.

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