CSCI 576

Spring 2026, University of Southern California | Instructor: Parag Havaldar

#The Visible Spectrum

The visible spectrum spans roughly 400-700 nm. Our eyes are not equally sensitive across all wavelengths — the photopic luminosity function $V(\lambda)$ peaks around 555 nm (green-yellow), which is why we perceive that region as the brightest part of the spectrum.

#Cone Sensitivity Curves

The three types of cone cells in the human eye each respond to a different range of wavelengths. They are commonly labelled by the Greek letters $\beta$ (short/blue), $\gamma$ (medium/green), and $\rho$ (long/red), corresponding to their peak sensitivities at approximately 441 nm, 543 nm, and 567 nm respectively.

#RGB

Each pixel contains three color channels: red, green, and blue. Each channel ranges from 0 to 255 (or 8 bits, since $2^{8} = 256$) representing the intensity of that color. By mixing different combinations of these three colors, we can create a wide spectrum of colors. You can even try mixing them yourself!