Weston Photronic Exposure Meter Model 617 Version 1, USA 1932:
The very first light meter made by Weston specifically for determining camera exposure. It is relatively rare since the twin cell model was only made for two years before being replaced by the much more compact single cell version 2. The example above is very early in the production run with a low serial number and a black cell button. No restoration of the instruction panel has been attempted.
Housed in black bakelite, as were all of Weston's meters of this time, it is a truly beautiful piece of engineering. It is designed for reflectance use only, where you measure the light being reflected off the subject rather than the incident light falling onto it. The central top groove aids in the sighting of the meter towards the subject. When the meter was used in its more sensitive twin cell mode the light values on the meter scale were divided by 10.
The disc to the left of the meter gives basic instructions for use. That to the right is the calculator dial of a basic design common to most of the Weston meters leading up to the very last models manufactured.
The plate / film speeds listed on the dial go up to only 48 - the maximum possible at the time of manufacture. Once this is set, another concentric dial brings the pointer to the measured luminance value. Aperture and shutter speed combinations can then be read off. Besides the normal pointer on the dial, there are others for different types of scene. They allow for exposure compensation for subjects of abnormally high and low contrast and brightness levels.
The original Model 617 Weston used a metal baffle mounted on the photovoltaic cell to make its response more directional. Weston exposure meters from the model 650 onwards used a glass lenticular system to provide that directionality. The lenticular arrangement also delivered more light to the cell, rendering the meter more sensitive.
This shows a basic non-invasive restoration of the instruction panel legend on an early production example of the 617/1. The lettering is slightly recess molded into the Bakelite and the original ink had flaked off with age. It has been restored with white water-based poster paint. A chinagraph should also work well.
The second variant of the 617/1 has a more durable riveted on instruction panel and a white, rather than black, cell selector button. This example is one of the much rarer mottled olive green examples produced alongside the standard black bakelite models.