Monday 28 September 2015

The Gossen Bisix Exposure Meter - a 1950's design classic

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The 1950's Gossen Bisix photographic exposure meter is a wonderful example of engineering design. Small, very lightweight and functional. Manufactured in West Germany, the meter requires no batteries, as it uses a selenium photovoltaic cell to produce a current from incident light. The current flows into a sensitive moving coil ammeter, the needle of which moves over a scale graduated 1 to 10.

The selenium cell has an ingenious corrugated transluscent screen, which can be moved using a side mounted slide to cover the cell. When uncovered, reflected light is measured. When the diffuser blind is used, incident light is measured.

These days, we take for granted the computing power of silicon integrated circuits to perform calculations. The Gossen Bisix however, designed long before ICs were invented, uses a purely mechanical computer! Beautifully simple, two moving parts, no batteries, nothing to go wrong! In order to determine shutter speed, the film speed is "dialled in" using the top ASA/DIN tab. Then the reading from the meter is dialled in by rotating the computation disc at the left hand side. On the right hand side, you choose your aperture on the fixed scale and, alongside on the computation disc, is the shutter speed! Simplicity itself. 

This particular meter has a serial number 012696, indicating that it is quite an early example - the type 1 being serialised 0 - 50000, before being superseded by the Gossen Bisix 2. It's in perfect working order, as can be seen in the following video, not bad for something I believe was designed in 1953. It's robust!

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"Hodges emitted a scream the like of which
I hadn't heard since his scrotum was burned off
during my experiment with fluorine gas last year."

The Exotic Experimentation of Ernest Glitch,
Victorian Science with a Smile

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Unrelated to this post, below is an example of
eclectic science esoterica 

Snowflake 300um LTSEM
Rime frost on both ends of a "capped column" snowflake

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WARNING - Many subjects outlined within this site are extremely dangerous and are provided here for information only. Please don`t experiment with high voltages or chemicals unless you are fully conversant with safe laboratory practices. No liability will be accepted for death, injury or damage arising from experimentation using any information or materials supplied.