Color perception
Rods and cones act as filters on the spectrum
•To get the output of a filter, multiply its response curve by the spectrum, integrate over all wavelengths
–Each cone yields one number
•Q:  How can we represent an entire spectrum with 3 numbers?
S
M
L
Wavelength
Power       
•A:  We can’t!  Most of the information is lost.
–As a result, two different spectra may appear indistinguishable
»such spectra are known as metamers
»http://www.cs.brown.edu/exploratories/freeSoftware/repository/edu/brown/cs/exploratories/applets/spectrum/metamers_guide.html