The Digital Photography Visiometer System(DPVS) measures visibility through emulating man's eyeballing,so it is more objective compared with traditional transmission or dispersion visiometers.To explain the working principles of DPVS hardware,the detailed description is given of control-circuit principles,circuit structure,choice of elements,circuit design ideas and a series of problems encountered in the operation of DPVS,as well as some application software about the single-chip processor in control circuits.