I just came across your extension. First, overall it's excellent, and using the preferred model of Brettel/Viénot et alia for protanopia. Too many CVD sims (like coblis) use inferior and inaccurate models.
Achromatopsia
When it comes to rod-only achromatopsia or blue cone monochromacy, they do not simply "see a grayscale", and BCM does not see a representation of a linear blend of normal, either.
A grayscale produced from sRGB luminance is by definition going to be a grayscale of the full range of humanly visible light. However rod response is not that full range, but a much narrower range, peaking at a wavelength that we might refer to as teal.
See the dotted line in this chart for the normalized rod response.
Of course we know that the rod response is substantially different in amplitude than the cone response, and reaches a maximum "bleaching" at around 8cd/m². Also we know that because of the way the rods are grouped together, that the effective resolution is substantially lower than the L or M cones.
As a result, those with rod-only achromatopsia has both severe photophobia, necessitating sunglasses even indoors, and low vision, typically not correctable to any better than 20/70.
BCM is not much better, as the S cones are sparsely scattered in the periphery, and are therefore also low in resolution.
POPULATION: Rod-only achromatopsia is about 1 in 33,000 and BCM is about 1 in 100,000.
NEURO: Achromatopsia that is caused due to a neurological issue, such as a stroke that damages V8 of the visual cortex, would likely see the full-range luminance greyscale without the chroma.
Simulation
I have an experimental BCM simulation at myndex.com/CVD/ based on the ideas of Brettel, but also includes a low vision and photophobia simulation. The balance between S cones and rods is an open question, and I'm thinking it might make more sense to show rod-only instead.
Thank you for reading, please let me know if you have any questions.
Hello,
I just came across your extension. First, overall it's excellent, and using the preferred model of Brettel/Viénot et alia for protanopia. Too many CVD sims (like coblis) use inferior and inaccurate models.
Achromatopsia
When it comes to rod-only achromatopsia or blue cone monochromacy, they do not simply "see a grayscale", and BCM does not see a representation of a linear blend of normal, either.
A grayscale produced from sRGB luminance is by definition going to be a grayscale of the full range of humanly visible light. However rod response is not that full range, but a much narrower range, peaking at a wavelength that we might refer to as teal.
See the dotted line in this chart for the normalized rod response.
Of course we know that the rod response is substantially different in amplitude than the cone response, and reaches a maximum "bleaching" at around 8cd/m². Also we know that because of the way the rods are grouped together, that the effective resolution is substantially lower than the L or M cones.
As a result, those with rod-only achromatopsia has both severe photophobia, necessitating sunglasses even indoors, and low vision, typically not correctable to any better than 20/70.
BCM is not much better, as the S cones are sparsely scattered in the periphery, and are therefore also low in resolution.
POPULATION: Rod-only achromatopsia is about 1 in 33,000 and BCM is about 1 in 100,000.
NEURO: Achromatopsia that is caused due to a neurological issue, such as a stroke that damages V8 of the visual cortex, would likely see the full-range luminance greyscale without the chroma.
Simulation
I have an experimental BCM simulation at myndex.com/CVD/ based on the ideas of Brettel, but also includes a low vision and photophobia simulation. The balance between S cones and rods is an open question, and I'm thinking it might make more sense to show rod-only instead.
Thank you for reading, please let me know if you have any questions.