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Web has a lot of references for human eye color sensitivity curves. Examples are

sensitivity enter image description here

This article:

J.J.Vos, Colorimetric and Photometric Properties of a 2° Fundamental Observer (1978) [3]

has a very different dataset that has maximum of the blue channel sensitivity at about 33 times lower compared to the maximum of the green channel sensitivity. This paper also has the red channel maximum higher than the blue channel maximum, and the second graph above has them all the way around.

What is the current best state of knowledge about spectral curves of RGB channels of human eye?

Are there numerical tables that approximate these spectral curves?

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    $\begingroup$ What do you mean by "sensitivity"? I think you'll find these charts are all using different measures rather than conflicting in any substantial way. And what is your ultimate goal: what do you want to do with this information? $\endgroup$
    – Bryan Krause ♦
    Oct 12, 2022 at 20:35
  • $\begingroup$ By sensitivity I mean the amount of perceived brightness per photon of light. The purpose is research is color perception. I have some ideas about how to improve computer cameras' color perception and would like to have an accurate information on how human vision perceives light. Corresponding sensitivity curves for cameras are called "quantum efficiency" and are typically published in camera specifications. $\endgroup$
    – Jennifer M.
    Oct 12, 2022 at 21:00
  • $\begingroup$ If you want to know about perception, then you will want to study perception, not the sensitivity of individual cones, and you don't need to know about different receptor types at all but rather about perceptual sensitivity itself. There's also a big difference between sensitivity in terms of "can you detect a brief, dim flash" versus discrimination: can I tell this color from that color. Both are going to be complicated by conditions in ways that a physical camera is not. $\endgroup$
    – Bryan Krause ♦
    Oct 12, 2022 at 21:05
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    $\begingroup$ I'm not saying the question is meaningless, I'm saying it needs to be made precise, and that if you want to know about perception it's wrong to base your measurements on photoreceptor cells in the retina. The perceived brightness of a blue light of fixed intensity and a red light with fixed intensity will depend on a lot: how bright is the room, and what color light illuminates it, or is it completely dark? If completely dark, for how long before the stimulus? Is it a flash or constant light? etc... Perception isn't a camera. $\endgroup$
    – Bryan Krause ♦
    Oct 12, 2022 at 22:02
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    $\begingroup$ I understand this. For flash vs. permanent light there should be two different spectral graphs. For low vs. high intensity there again should be two different spectral graphs. When the light hits the retina it creates some effect that depends on the wavelength. I am interested in the intensity of that effect depending on wavelength and type of sensing cell (RGB). $\endgroup$
    – Jennifer M.
    Oct 13, 2022 at 0:15

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The graph of same amplitudes is called a normalized view, the peak of the three graphs is multiplied to 1.0... It doesn't really matter about the individual cone/rod efficiency because there are different counts and ratios of them as necessary.

The relative spectral sensitivities of the five photoreceptors in human retina, including S-, M-, L-cones, rods, and ipRGCs (A), LED spectral distributions (B), and LED chromaticities in CIE color space. (ref 2015) enter image description here

Scientists use spectral photometry of cells and measure their response, so that's the field you can study to know the spectral sensitivity.

The brain/ganglions can adjust for differences to give a balanced/optimized mix, and there can be 2 times more of a specific receptor cell type if it 0.5 times as receptive, so the perceived view is more or less psycho-normalized to see white accurately.

Current understanding is that the 6 to 7 million cones can be divided into

  • "red" cones (64%),
  • "green" cones (32%),
  • "blue" cones (2%)

based on measured response curves. They provide the eye's color sensitivity. The green and red cones are concentrated in the fovea centralis . The "blue" cones have the highest sensitivity and are mostly found outside the fovea, leading to some distinctions in the eye's blue perception.

The cones are less sensitive to light than the rods, as shown a typical day-night comparison. The daylight vision (cone vision) adapts much more rapidly to changing light levels, adjusting to a change like coming indoors out of sunlight in a few seconds. Like all neurons, the cones fire to produce an electrical impulse on the nerve fiber and then must reset to fire again. The light adaption is thought to occur by adjusting this reset time.

The cones are responsible for all high resolution vision. The eye moves continually to keep the light from the object of interest falling on the fovea centralis where the bulk of the cones reside.

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