Vision and the human eye . Rods and cones. History of camera and image processing. Greater sensitivity of human vision to grayscale, but greater resolution to color.
Cones are mostly in fovea, central region of retina.
Digital image sensors . Sampling and quantization. Shot and thermal noise. Quantization refers to finite number of gray levels or colors used to represent the signal at each pixel. Shot noise results from quantum effects of light sources, usually manifest at low light levels.