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[OM] Re: OLYMPUS 49MM SHADE WITH POWER BOOSTER CELL

Subject: [OM] Re: OLYMPUS 49MM SHADE WITH POWER BOOSTER CELL
From: Jim Brokaw <jbrokaw@xxxxxxxx>
Date: Thu, 22 Apr 2004 23:57:15 -0700
Selenium cells respond to light falling on the surface, more light = more
current generated. In low light levels, below a certain threshold there
isn't enough current to move the meter needle... add more cell area and more
current is generated, but a built-in meter only has so much area to use for
cell, so add-on cells were a technology used some to boost sensitivity.
Typically you'd use a different index mark on the calculator dial when using
the booster cell. Leica made a booster cell for the early selenium Leica
meter, since the meter alone was small to mount tidily on the flash shoe.
Almost all these old cells are 'dead' now, the selenium loses electrical
generating ability after decades and light exposure.
-- 

Jim Brokaw
OM-'s of all sorts, and no OM-oney...


on 4/22/04 9:26 PM, Gordon J. Ross at gordross@xxxxxxx wrote:

> Hi Jim:
> 
> That is sounding good, but why would a built in meter need a booster?  Even
> if it is dead, think how cool your rig would look with that bad baby hanging
> off the hood.
> 
> Gord
> ----- Original Message -----
> From: "Jim Brokaw"
>> Looks to me like two things... the lens hood (shade) appears to be like
>> those for the Olympus Trip 35 and 35-RC. The other 'mystery' element looks
>> like a selenium booster cell for an old light meter... either a hand-held
>> meter or perhaps a booster for a built-in meter in an old camera. From the
>> look of it I'd say maybe late 1930's to 1950's era. If it is a selenium
> cell
>> the age means its probably died by now.
>> -- 
>> 
>> Jim Brokaw
>> OM-'s of all sorts, and no OM-oney...


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