[pure-silver] Re: Bulb for Focomat IIc

  • From: "Edward C. Zimmermann" <edz@xxxxxxx>
  • To: pure-silver@xxxxxxxxxxxxx
  • Date: Thu, 21 Dec 2006 08:26:36 +0100

Quoting "Gary W. Marklund" <Gary@xxxxxxxxxxxx>:

> You don't want a regular household bulb because the brand/size 
> printing on the end of the bulb can/will become a part of your print.

Impossible as its not in the plane of focus. What gets focused is the
negative.

The IIc is a half-condenser design.

The light source is diffuse (the opal bulb) and it then gets condensed.
On the scale of [cold light] to [point source] the IIc is even a more
diffuse than the Ic (Ia, I, Valoy etc.) which use the condenser as
film (pressure) plate--- the IIc has a glass negative carrier and some
distance between the (completedly enclosed) condenser unit.
 
> My 1C calls for an Opal 75 watt. So, I guess the 211 is what you want.

The Ic does not call for 75w (earliest documentation suggested 75w given
heat and the very long exposures demanded by then contemporary papers) but
is (in general) suitable also for 150w. Later versions (more elongated, egg
like shaped, versus nearly round) were explicitly also for 150w and most
that saw commercial action got 150w bulbs (time was and still is money).

Standard for the IIc was always the 150 watt bulb.

Because of the design of the IIc its still best to use opal photographic
enlarger bulbs (they should not be too expensive, if need be sourced from
old stocks, swap meets, auction sites etc.). These bulbs work well and last
quite a long time. Opal bulbs don't go bad with age (well they can and do
but lets not be too nit-picky) so even a 50 year old bulb will still
(probably) work.

> Gary
> 
> 
> 


-- 
-- 
Edward C. Zimmermann, Basis Systeme netzwerk, Munich
http://www.nonmonotonic.net
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