Abstract: The present invention relates to an image processing method for enhancing the digitised optical image section of a (e.g. substantially transparent biological) specimen and in a particular aspect the boundary outline of a specimen in such an image section thereof. In accordance with the invention a Nomarski image section is smoothed and a gradient of image pixel intensity determined for each pixel thereof. Thereafter each pixel of the smoothed Nomarski image which has an intensity gradient within a reference range is set to zero intensity so as to provide a processed image section.