[pure-silver] Re: Bulb for Focomat IIc
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 20 Dec 2006 23:35:40 -0800
----- Original Message -----
From: "Edward C. Zimmermann" <edz@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, December 20, 2006 11:26 PM
Subject: [pure-silver] Re: Bulb for Focomat IIc
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
I'm not sure how the light source for the Focomat works
but for some condenser enlargers, like my Omega D2V, the
condenser is focused approximately at the entrance pupil of
the lens. The markings on the end of a bulb may not be in
sharp focus but will still be visible. Again, opal lamps
have a different diffusion surface, this is important for
many enlargers particularly for condenser types where the
large, very diffuse, surface of the lamp is focused as
indicated above on the lens. These are really partially
diffusing enlargers with the diffusion coming from the lamp.
If a plain reading lamp is used there will be a hot spot.
Even some diffusion enlargers depend on the lamp itself
being rather diffusing to avoid uneven illumination.
Of course, you can always try a reading lamp in the
enlarger. If it works OK you are home free but beware that
it may not work very well.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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