Background

To understand how the cone systems relate to color perception, consider the following: A monochromatic light at 500 nm (green) is projected onto a white piece of paper. When the reflected light strikes the retina, there will be a very weak response in the S-cone, a strong response in the M-cone, and a relatively weak response in the L-cone. It is this pattern of responses that induces the experience of the color green. Each different color produces a unique and different set of responses on the cones. In a metameric match, two different sets of wavelengths produce the same responses on the cones creating the perception that both sets of wavelengths produce the same color. From this perspective, they actually do produce the same color.

In this activity, you can change the wavelength of a light and see how different wavelengths produce the different relative activities on the different cones.

Instructions

Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab

Settings

Below is a list of the ways that you can alter the model. The settings include the following:

Color: a simulation of the color seen with this wavelength of light.
Wavelength: change the wavelength of the light that is stimulating the cones. The wavelength is indicated by the vertical line in the cones graph on the left. The relative level of activity in each cone is shown in the bar graph.

Reset

Pressing this button restores the settings to their default values.

Color

The graph on the left shows the sensitivity of the different cones to a wide range of visible wavelengths. The bar graph shows the relative level of activity of each of the three cone classes to the current wavelength. A simulation of the color is shown in the square above the slider. You can change the wavelength with the slider above. The wavelength is indicated by the dark vertical line on the graph on the left.