In use the film speed is set to one of the film speed groups and the aperture is set. On taking the reading the shutter speed is indicated by the pointer moving over a dial. Setting the aperture alters an iris diaphragm (made of thick paper) close to the selenium cell. On the cine version the film speed and f.p.s. are set and the needle shows the aperture.

In use the film speed is aligned to the meter needle by turning a dial. The shutter speed and aperture pairs can then be read. Channels lie between the needle window and the dial. The Eos was a cheap photoelectric meter at only 50/- but less sensitive than the Tempiphot and Tempophot also by Metrawatt.

The light enters the cell through a serrated aperture that protects the cell from strong light. For use in weak light an angled mirror deflects light onto the cell, a different index is used in this case. A detachable amplifier can be fitted for use in low light conditions. The price was £5.5.0. Also produced in a cine version called the H60K.

In use the film speed is set on the calculator. The reading is taken, the shutter speed is set against the meter needle by moving a dial on the front of the meter. Indices on the dial then point to the aperture. Similar in use to the Tempiphot.