NOTE: Colors are for illustration only, and are not calibrated.
left plots show efficiency curves of the two cone pigments, overlaid with the lines
indicating wavelengths of reference (dashed) and two test light components
right bars show total # of quanta absorbed in each cone pigment for reference and test lights
(simply efficiency * light intensity )
left sliders control wavelength of reference and two test lights
right sliders control amount of each light (# quanta)
1. First, don't touch the wavelength controls on the left.
Just adjust the amounts of the test lights (two sliders on the bottom right.)
Can you match (approximately) the M and L levels of the reference light? (Match the heights of each pair of bars.)
If so, you have made a metameric match to the monochromatic reference
light with the two test lights for this dichromatic observer. An observer with
only the two pigments depicted would not be able to discriminate the reference wavelength from the mixture of the two test wavelengths.
2. Now adjust the second test light (labeled 'c') to around 480 by moving the bottom left slider to the left.
Again, try to find the match by adjusting the intensities. You may need to set one of the primaries to a negative value. What does this represent in a real experimental context?
These demos show that a dichromat can match a reference wavelength with any
combination of two wavelengths. Equivalently, they are unable to
discriminate the mixture from the reference based on color.