This program was initiated to develop a method and apparatus for determining the oil drop size distribution in flowing oily brine during brine cleanup treatment. An automated photomicrographic apparatus for taking time-lapse photographs of oily brine that was briefly at rest is described. This apparatus meets all N.E.C. Class 1, Division 1, Group D requirements for operation where explosive concentrations of hydrocarbons are known to exist. The system demonstrates its ability to determine the size and number distribution of 2- to 100-micrometer spherical entities, and it establishes their density as well. Thus the technique can differentiate between oil drops, oil-covered gas bubbles, and oil-covered sand or other solids. The report presents both the techniques for reducing the photomicrographs to size and number data, and the Fortran programs involved. Although developed for oil particles in brine on offshore production platforms (where the device has obtained some 20,000 photos for the parent study), the apparatus and technique are equally well suited for characterizing the distribution of any immiscible minor component in a semi-transparent fluid matrix.