Dany
No longer a newbie, moving up!
- Joined
- Dec 13, 2011
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- 291
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- 575
- Location
- Paris
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This can be considered as one of the ancestors of the light cells used today in photography.
The "Posographe" is in fact nothing else that an analog mechanical computer able to tell you which exposure time is to be used depending on many parameters as the type of film, the available light, the diaphragm, the time of the day, the location, the type of subject etc...
Elaborated in France by Mr Kaufmann circa 1922, 1923 the Posographe measures apprx 13 x 8 cm.
The instrument shows a metal frame with sliding indexes on each four sides of the frame.
The frame is supporting two panels installed back to back. One is dedicated to outdoor photography, the second one show parameters for indoor photography.
Between these two panels, an hidden and complicated set of levers is linking the different sliding indexes.
The photographer choose the face of the instrument (indoor or outdoor), give the correct position of the different parameters indexes and read the exposure time .
I bet Mr Kaufmnn suffered a lot of headaches designing the correct form and combination of the levers. But he did it and it gives a nice example of 1920's engineering.