1. A system for analyzing fluid comprising: a housing having first and second opposing surfaces spaced to form a fluid chamber; a light source disposed to direct light at the first surface of the housing; a digital imaging circuit disposed to detect light at the second surface of the housing, said digital imaging circuit having a pixel array configured to capture one or more digital images of an illuminated fluid; and a processor configured to: capture multiple digital images of the light through the fluid at different camera exposure levels; calculate a net radiant energy value at each of a plurality of different integration times within at least two images; calculate a slope of the net radiant energy values with respect to integration time in a selected image; and determine a particle size distribution and volume fraction of particles within the fluid based on the calculated slope.