In the days before exposure meters became the norm a whole range of calculators were available to enable the correct exposure to be determined in both day light and artificial light. Some were film or camera make specific, such as those by Kodak, whilst others were generally applicable such as the range made by Johnson of Hendon in the UK.
The Imperial Exposure Meter No 1 For Bright Light made by the Imperial Dry Plate Co Ltd, Cricklewood, London NW. The “meter” itself was a strip of sensitised paper which darkened when exposed. The time it took to darken to the right shade was noted. The slide was then moved so that the H&D speed number lined up with the Actinometer time. The exposure time could then be read off against the selected f number. Patent No 3873 - 1901.
Kodak Indoor Exposure Guide for Kodak roll films and film packs and Mazda photoflood lamps. No 1, 1939.
Plastic coated card. Eastman Kodak Co, Rochester, New York. Enables aperture & exposure time to be determined for various lamp and distance combinations. Also a photoflash calculator for time exposures.
Plastic coated card. Eastman Kodak Co, Rochester, New York. Enables aperture & exposure time to be determined for various lamp and distance combinations. Also a photoflash calculator for time exposures.
Kodak Indoor Guide for black and white films. Kodaguide 1218 8-41-CH-BEX. Eastman Kodak Co, Rochester, New York. The front side is again used for calculating photoflood exposures but there is now an aperture on the reverse for determining aperture with synchronised or unsynchronised flash for various flash bulbs. Both this and the previous guide were obtained from the USA.
Johnson Flash Exposure Calculator. Celluloid. It was used rather like a telephone dial. After setting the arrow against ‘start’, first the type of flash was dialled in, then the calculator was turned over and the film speed dialled, followed by the shutter speed. The aperture could then be read off against the appropriate distance. There were special instructions for electronic flash.
Johnson Colour Exposure Calculator for Cine and Still Reversal Films BS935. It was used in a similar way to the flash calculator above. First the disc was rotated until the film speed showed in the window, then the calculator was turned over and the light value was dialled in after selecting it from the table. Then, on the front again, the shutter speed (still) or taking speed (cine) was dialled and the aperture read against the type of lighting. It has a paper envelope and instruction sheet. Introduced in 1957. Plastic, probably celluloid.
“Wellcome” Photographic Exposure Calculator, Handbook and Diary 1936. Mint condition and unused, The data for use with the disc calculator in the back cover is obtained from the tables on the pages of the handbook.
Johnson Standard Exposure Calculator for Black & White & Colour Negative Films in Daylight. Another calculator from the range of Johnsons of Hendon Ltd. It also has its paper envelope and instruction sheet, the latter with a printing date of 1968. Construction is the same as for the Colour one above. In use first the filter factor was set against ‘start’, then the subject group was selected and dialled to ‘stop’. Then the calculator was turned over and the light value, the film speed and weather conditions successively dialled. Then on the front of the calculator the shutter speed could be read off against the chosen aperture.
Johnson Standard Exposure Calculator. This was the earlier form of the “Standard” calculator, dating from the early 1950s. Its construction is the same as the Flash calculator. It is made of Ivorine (Celluloid). Its operation was similar to that of the later model but using Time rather than Light Value.
Johnson Artificial Light Exposure Calculator made of Ivorine, same size and constructions as the Flash calculator, made in the 1950s. It is complete with paper envelope and instruction leaflet.