The Photomic Prism/Meter Finder System combines a roof prism and a sensitive CdS meter cell in a single housing. This cell is energized by a standard mercury battery, and is capable of measuring as little as 1/10 foot-candle of light. The Photomic meter covers film speeds from ASA 10 to 1600. It can also be preset to compensate for filter factors uo to 4X. A screw-in opaline disc is available for taking incident light exposure readings, where desired.