First Johnson Exposure Calculators

Standard Calculator

 

Northern Hemisphere
'Standard' Calculator (front)

Northern Hemisphere
'Standard' Calculator (back). The indistinct text at the bottom reads:
Times given are local solar time which may not be official time and must be converted. For example, in England, 3pm
= 3pm Greenwich Mean Time (GMT) = 4pm British Summer Time (BST)
= 5pm Double Summer Time (DST)

Southern Hemsiphere
'Standard' Calculator (front) -
(RH)

Southern Hemisphere
'Standard' Calculator (back - note "Latitude S" on LHS)
Also, there is no guidance about GMT, BST or DST. -
(RH)

Artificial Light Calculator

'Artificial Light' Calculator (front)

'Artificial Light' Calculator (back)
   

The calculators, when purchased individually, were supplied in small paper envelopes, such as the one shown above, 7.5cm square.
The 3/- (3shillings, 3s, = 15p) price is clearly marked.
The instructions are shown below.

A rather more colourful version of the artificial light calculator was available by the late 1950s.
But the price had risen to 4/6d = 22.5p
The 1958 instructions (see below) were more detailed.
   

   

Artificial Light Calculator ~ French version; courtesy of Daniel Clement

   

BJPA Review of the Artificial Light Calculator, July 1949, p305


This page last updated: 4th April 2019