An inexpensive microphotometer system for measuring silver grain densities in autoradiographs.

An inexpensive microphotometric system is described which will facilitate reading grain-dense areas in autoradiographic material. It is reliable, easy to operate and adaptable to most light microscopes with a dark field condenser. In addition to the microscope, the components include a photodiode, an operational amplifier and a digital mV meter. Data are presented to demonstrate the sensitivity of the system and to illustrate the differential variability between the microphotometer and the counting of grains by eye.