1. A method for determining a distribution of a parameter of a particle population comprising the steps of: a) detecting on a pixel array of elements a plurality of images of the particles; b) determining a number of pixels in the form of a pixel count corresponding to each of the plurality of images of particles; c) obtaining a plurality of weighting factors which relate values of the parameter to different pixel counts; and, d) utilizing the plurality of pixel counts and the weighting factors to determine the distribution for the parameter of the particle population.