In Homomorphic filter multiplicative noise is changed to an additive noise. To attain this, the illumination reflectance model is used where the image is modeled as the product of illumination i(x, y) and reflectance r(x, y) components.

Let f(x, y) = i(x, y)r(x, y) where $0\lti(x, y)\lt∞ and 0\ltr(x, y)\lt1$ …