FIGURE 9-6 Range and Peak Sensitivity Our color perception corresponds to the summed activity of the three cone types: S cones, M cones, and L cones (for short, medium, and long wavelengths). Each type is most sensitive to a narrow range of the visible spectrum. Rods (white curve) prefer a range of wavelengths centered on 496 nm but do not contribute to our color perception. Rod activity is not summed with the cones in the color vision system.