In use an index for the time of year is set against the type of film in use. The time of day is set against an index which incorporates filter factor settings. The type of subject is then set against the sky condition. The shutter speed and aperture pairs can then be read.

Light curves are drawn for different months of the year. To use, a pointer is set to the environment (subject and sky condition). A subject number is read in a window, six numbers are shown for different subject distances. A cursor is set to the appropriate subject number which are printed on the edge of the meter. The meter is then turned over and a dial moved so that the month curve intersects the cursor which carries a time of day scale. An inner disc carrying the film speed is moved to the sky condition. The shutter speed and aperture pairs can then be read. The price was 10/6.