Monochrome image
Intensity l: Lmin ≤ l ≤ Lmax. In practice:
Lmin=imin rmin and Lmax = imax rmax
Typical limits for indoor values in the absence of additional illumination:
Lmin ≈ 10 and Lmax ≈ 1000
[Lmin , Lmax] is called the gray (or intensity) scale
Common practice: shift to [0, L-1], where l=0 is considered black and l=L-1 is considered white