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3D3DPhotographic ribbon holder.
You might call this the world's slowest flash bulb. In the early days of photography film was not very sensitive and high-power flash lamps were not available. Exposure times would often be many seconds long, hence the stiff, formal look of portraits from that time: They were trying not to breath. Magnesium powder was used in flash powders (where the photographer held a pan up over his head and lit it, resulting in a bright flash and a poof of smoke). A safer, more controllable alternative was to use magnesium ribbon, which burns very brightly, and at a consistent rate. The idea behind this holder is that you use it to measure out a predetermined length of ribbon, calculated to generate the amount of light you need to expose your film (based on the brightness and the rate at which the ribbon burns). You pull that much ribbon out of the holder (which has a spool inside), then light it. When the flame reaches the tip of the holder, it goes out, automatically timing your exposure. In other words, a slow-motion flash bulb.
I paid a lot of money for this, $100, but that seems to be the going rate: Several similar ones have sold on eBay in this price range, and this is a really nice one with the original box and instructions intact.
Source: eBay seller sport1
Contributor: Theodore Gray
Acquired: 15 December, 2003
Text Updated: 29 January, 2009
Price: $100
Size: 4"
Purity: 99%
Magnesium