JOHNSON ARTIFICIAL LIGHT EXPOSURE CALCULATOR
Johnson Artificial Light Exposure Calculator, made of Ivory, is the same size and construction as the Flash calculator, which was made in the 1950s.
Circa 1950

Before exposure meters became the norm, a wide range of calculators were available to determine the correct exposure in both daylight and artificial light. Some were film or camera make specific, such as those by Kodak, while others were generally applicable, such as the range produced by Johnson of Hendon in the UK.
In late 1946 (RH), Johnson & Sons, Manufacturing Chemists Ltd, began marketing a ‘British Standard’ (to BS 935/1941) 6.5cm diameter rotary exposure calculator made of ‘ivorine’. This plastic simulates the appearance of ivory. It was reviewed in the 4th December 1946 issue of the British Journal of Photography (BJP) on p132. “Packed in a stout envelope, with full instructions, the price is 4s/2d (21p) including Purchase Tax” (PT). The full review and the Johnsons’ advert in the 1947 BJP Almanac are viewable here.
The Johnsons of Hendon advert in the 1949 BJP Almanac shows that an Artificial Light Calculator of similar appearance had then joined the Standard calculator. By the early 1950s, they were priced at 3/- each (15p) or could be purchased as a pair in a ‘neat plastic leather-grained purse with press-button fastener’ specially made to hold the two calculators, priced 8/- (40p).
Of course, there was nothing novel about these calculators. Many organisations supplied some form of exposure calculator, and the rotary format was relatively standard. Ilford marketed such a device from as early as 1896 (RH). Contemporary to the Johnson calculators, the ‘Focal Press’ supplied a neat 3-fold exposure guide with a rotary calculator, including advice on stage, flash, nighttime, artificial light, indoor daylight and colour photography. It had many reprints.
Prominent film-makers supplied, free of charge, simple pocket exposure guides, often laminated to improve their resilience. Indeed, the instruction leaflet packaged with films contained a guide to exposure that was perfectly adequate for most outdoor subjects in daylight for many years. Special guides were published for events like bonfire night (5th November) and street scenes of Christmas decorations. They encouraged people to use their cameras under more unusual circumstances, which was suitable for product sales.