Artificial Light Exposure Calculator.

[daveh]

This was sold by Johnsons in the 1960s (ish), and is a surprisingly accurate system for determining artificial light exposure. In the day's before everyone had a capable exposure meter it really was a boon. It was used by moving the toothed wheel the necessary amount for the prevailing conditions and film speed. Mind you I wonder what ISO 400 is on the Scheiner system (I presume this was the one used by Ilford).

[colray]

I remember those calculators.

[PeterW]

Dave, your picture of the Johnsons exposure calculator brought back a lot of memories. You’re a little late, though, in your “ish” dating.

Johnsons brought out the dial calculator soon after they took over publication on the Wellcome photographic diary in 1945. This had a cardboard circular exposure calculator on the inside of the back cover. Johnsons continued with this, but also simplified it by bringing out four separate versions, Daylight, Artificial Light, Flash and Cine in white plastic.

They were useful calculators but slow to use. By the time you dialled all the information and arrived at an answer the chances were the picture had passed by or the light had changed.

In about 1960 Johnsons met complaints that it was easily damaged by giving it a stronger square back opposite the finger-dial serrations.

Here’s a pic from my website of the cardboard calculator in the back of the 1947 diary, together with the 1947 Daylight version of the separate plastic calculators



PeterW

[daveh]

I've just found an excellent webpage www.mathsinstruments.me.uk/page67.html about these calculators. It seems that the square backed version came out in 1957. The last date it gives to one version was 1968.

Johnson's of Hendon was a famous name in British photography. An interesting history of them can be found at www.photomemorabilia.co.uk/Johnsons_of_Hendon/Johnsons_of_Hendon.html