Archived posting to the Leica Users Group, 2002/11/28

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Subject: Re: [Leica] Time-line: focal length in centimeters versus millimeters on projection lenses, Epidiaskop IIIs
From: "Willem-Jan Markerink" <w.j.markerink@a1.nl>
Date: Fri, 29 Nov 2002 03:39:59 +0100

On 28 Nov 2002 at 18:01, Greg J. Lorenzo wrote:

> Hi Willem,
> 
> Are you sure this thing's a Slide Projector?

:))
Not just, also a book-projector....slides are secondary (only 1 of 
the 5 1500W lamps....;)).
My first 'contact' with the enemy was by reading about a British 
auction....was a bit miffed at first, it read 'epidiaskop, should be 
collected by 3 strong men'....knowing the weight of an ordinary 
Epidiaskop, I almost decided that Pommies were wimps, until I read 
about 2 or 4 lamps....:))
Some time later, I talked to the largest projector collector in 
Germany, and he once saved the diascopic part of such a IIIs, one 
from 3 units that were about to be send to the crusher....no wheels, 
nobody wanted them (try moving 300-500kg of this size without 
wheels)....
A few months later I found, also in the UK, a piece of Leitz 
literature that described several academic projectors, and to my 
great luck it featured the one and only official picture of a IIIs 
that I have today.
(my kingdom for a factory brochure and price list!)
(do have a 1930'ish Dutch pricelist for the smaller Epidiaskop's, a 
rare find too) 

> It looks more like one of the Search Lights used by the Germans to
> find Allied bombers at night.

My (pure) 500/5.7 Diaskop looks more like a piece of artillery....and 
that is a mild lens, compared to the 1000/6 (never actually seen a 
version above 700 or 800mm, would love to know production data of 
each model).

Btw, slides are inserted horizontally in the mid-section (unlike the 
smaller (epi)diaskop's), the diaskop lamp is sitting on the rear, 
beaming forward, onto a mirror, beaming upward, through the slide, 
onto another mirror, beaming forward into a condensor, and then into 
one of the two upper lenses.
The wooden sliding doors below (one on either side) are for the 
episkop section; lamps beaming downwards onto the paper/book at a 
slight angle (one lamp in each corner); reflective light beaming 
upwards, onto a huge mirror, beaming forward onto the lower lens.
(no lenses in that picture, would have made transport even more 
difficult by another 50kg....8-))


- --                 
Bye,

Willem-Jan Markerink

      The desire to understand 
is sometimes far less intelligent than
     the inability to understand

<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]


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