Re: plate holders for dummies

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, July 13, 2004 12:54 PM
Subject: Re: plate holders for dummies

> From: "Adam. Waterson" <artistboi@speakeasy.net>
> Subject: plate holders for dummies
> Date: Tue, 13 Jul 2004 14:55:25 -0400
>
> > I was figuring that i'd just butcher a few normal 4x5
film holders
> > trying to figure out how to make it work. Does anyone
have a practical
> > resource for how to make a wet plate holder that still
fits into
> > traditional 4x5 spring loaded back.
>
> I'm not much older than you to be useful but plates need a
different
> mechanism to secure in the holder. I think most film
holders require
> film to be bent when placing but this is impossible with
plates. So
> plate holders usually have one side that is pushed in by
spring. A
> plate is pushed against that side when inserting. Then
there is
> problem with thickness of the base, and how to make up for
the plane
> of focus. That is, plate holder must have deeper well so
that the
> surface aligns with where the film was.
>
> --
> Ryuji Suzuki

   Film holders have a flat septum which locates the film
plane. The film is held by the edges in channels at all four
sides. These may put very slight pressure on the film to
curve it toward the septum. This is the direction the raw
film tends to curve anyway.
   Plate holders are essentially a frame whose edge forms
the reference surface for the plate. There is a spring at
the center of the holder which bears on the back of the
plate holding it against the frame of the holder. In the
distant past adaptors were made to convert plate holders to
shteet film. These are called sheaths. These consist of a
thin sheet of metal with channels around the edges. The
adaptor is designed so that the film surface coincides with
the surface of the plate. Sheet film 4x5 and larger sizes is
actually slightly smaller than the nominal size to allow its
use in such adaptors. Plates are the actual size given,
i.e., an 8x10 plate is actually 8x10 inches where 8x10 sheet
film is about 1/8th inch smaller in each direction.
   I don't think its easy to convert a film holder to a
plate holder although it may be possible. Plate holders show
up occasionally on the used market. Alan Brubaker makes
custom film holders and repairs older ones.

Alan Brubaker

awbent@filmholders.com

AWB Enterprises
33320 Gafford Road
Wildomar, California 92595
Tel/Fax: (909) 674-0466

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com