What are the I, B, L, and V components in HSI, HSB, HLS, and HSV?
To conform with the definition of luminance as being proportional to physical power, the I component of HSI should represent a linear-light quantity. The CIE has defined no objective measure for brightness, but it is clearly a perceptual quantity. Lightness is a perceptual quantity that has been quite precisely defined by the CIE. The CIE has not defined Value, but several different definitions are in use, such as Munsell Value, and all have a perceptual basis and are comparable to lightness. In most formulations of HSI, HSB, HLS, and HSV used in computer graphics, the quantities are computed from R, G, and B primary components but no reference is made to the nonlinearity in the primary components, that is, the relationship of the primaries to linear light. So it is impossible to determine whether the calculated HSI, HSB, HLS, or HSV represents a physical or a perceptual quantity. The brightness component of HSI, HSB, HLS, and HSV should be based on luminance, computed as a properly-we
