How many bits do I need to smoothly shade from black to white?
At a particular level of adaptation, human vision responds to about a hundred-to-one contrast ratio of luminance from white to black. Call these luminance values 100 and 1. Within this range, vision can detect that two luminance values are different if the ratio between them exceeds about 1.01, corresponding to a contrast sensitivity of one percent. To shade smoothly over this range, so as to produce no perceptible steps, at the black end of the scale it is necessary to have coding that represents different luminance levels 1.00, 1.01, 1.02, and so on. If linear light coding is used, the “delta” of 0.01 must be maintained all the way up the scale to white. This requires about 9,900 codes, or about fourteen bits per component. If you use nonlinear coding, then the 1.01 “delta” required at the black end of the scale applies as a ratio, not an absolute increment, and progresses like compound interest up to white. This results in about 460 codes, or about nine bits per component. Eight bit
At a particular level of adaptation, human vision responds to about a hundred-to-one contrast ratio of intensity from white to black. Call these intensities 100 and 1. Within this range, vision can detect that two intensities are different if the ratio between them exceeds about 1.01, corresponding to a contrast sensitivity of one percent. To shade smoothly over this range, so as to produce no perceptible steps, at the black end of the scale it is necessary to have coding that represents different intensity levels 1.00, 1.01, 1.02 and so on. If linear light coding is used, the “delta” of 0.01 must be maintained all the way up the scale to white. This requires about 9,900 codes, or about fourteen bits per component. If you use nonlinear coding, then the 1.01 “delta” required at the black end of the scale applies as a ratio, not an absolute increment, and progresses like compound interest up to white. This results in about 460 codes, or about nine bits per component. Eight bits, nonlinea
