The present invention provides a low cost imaged-based system for detecting, measuring and/or counting labeled features of biological samples, particularly blood specimens. In one aspect, the invention includes a system for imaging multiple features of a specimen that includes one or more light sources capable of successively generating illumination beams each having a distinct wavelength band and a plurality of differentially excitable labels capable of labeling a specimen comprising multiple features, such that each different feature is labeled with a different differentially excitable label.