The reading is taken which gives the light value between 1 and 7. This is added to a subject value printed on the meter. The combined value is set against the film speed, the shutter speed / aperture pairs can then be read. The Addiphot was sold by Wallace Heaton in 1939. The Photax example probably dates from the 1940s.

This is very similar to the Addiphot type of meter except it is made of wood rather than plastic and is larger. The reading is taken giving a number between 1 and 7. An adjustment is then made for the light condition from a printed table on the rear of the meter. Underneath the slide is a DIN/Scheiner conversion table. Made in England.