[pure-silver] Re: Can I interrupt for a minute?
- From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 12 Sep 2004 06:25:17 -0700 (GMT-07:00)
-----Original Message-----
From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
Sent: Sep 12, 2004 2:21 AM
To: PureSilverNew <pure-silver@xxxxxxxxxxxxx>
Subject: [pure-silver] Re: Can I interrupt for a minute?
Dave
Welcome to the world of 'real' photography. 4x5 is a great format and gives
flexibility, not achievable otherwise.
My experience is limited to used plastic holders. There are some difference=
s
between these holders, which is amazing, because I heard that they are made
by the same molder.
1. I'd stay away from the holders with the tiny numbering wheel. They will
fit your camera (I think) but they won't fit all.
2. The other difference is the manufacturing tolerance for these holders. I
made myself a device with which I can measure the location of the film plan=
e
and it's variation. I have measured over a hundred of these holders and
found them all to vary significantly but had the best luck with Lisco Regal
II, which have a simulated 'leather grain on the frame. Other holders,
having the 'tire-track' patterns on the frame where the worst.
The ANSI tolerance for 4x5 film holders is +/- 0.007 inches. Some holders d=
o
better, many are not to this specification. Of course, the important thing
is that the film is in line with the ground glass.
In his May/June 1999 Photo Techniques magazine article, Jack East Jr.
proposed a simple but effective alternate method to check whether the groun=
d
glass and the film plane are within acceptable tolerance.
Place a piece of film into a holder and insert it into the camera back.
Remove the back from the camera, and lay it flat on a table. Rest the edge
of a rigid ruler across the camera back. Hold a toothpick or cocktail stick
vertically against the ruler, lower it until it touches the film and clamp
or tape it to the ruler, thereby identifying the film plane location. After
doing this with all film holders, leave the toothpick positioned for an
average holder.
Now remove any film holder from the camera back, and compare the average
film plane with the ground glass location. If the toothpick just touches th=
e
ground glass, then no adjustments are required. Knowing that a sheet of
regular writing paper is about 0.1 mm (0.004 inch) thick provides a tool to
quantify any offsets. If the toothpick touches before the ruler, then you
could shim the ground glass with paper, but if there is an unacceptably
large gap between toothpick and ground glass, then professional machining o=
f
the camera back is required.
With the toothpick still positioned to identify the average film plane
location, measure all film holders for variation. According to the standard
a tolerance of =B10.007 inch, or two layers of paper, is acceptable for the
4x5 format. Discard or avoid film holders outside this tolerance.
Regards
Ralph W. Lambrecht
I have a large numer of older 4x5 holders. I've found the best of them are
the Riteway holders made by Graflex. I measure the film plane using a metal
plate and a depth gauge. I've found significant variation in the position of
the film plane both as to distance and as to warping. Wooden holders must be
carefully checked because they have a great tendency to become warped. I have a
bunch of Fidelity plastic holders from probably the 1950's. The film plane
position on all of them is substantially off. For 8x10 I cherry picked among
perhaps thirty holders to find ten or so that are accurately located. These are
mostly very old holders.
I believe you are correct that Riteway, Lisco, and Fidelity are all now
made by the same company.
For the ground glass position I use a similar technique to the one for
holders. The back of most view cameras comes off so its easy. Speed Graphic
backs can be removed. Its requires some work but I've done it to double check.
The reference surface in Speed Graphics is metal so its pretty accurate. You
can measure the depth of the ground glass panel from the corners to the glass
surface. On the original spring back the reference surfaces are the corners of
the panel.
The ISO-ANSI spec is for the septum in the holder. The actual film plane
position is 0.007 inch less. That is the thickness of most sheet film. I
ususally measure the holders with film in them.
Richard Knoppow
dickburk@xxxxxxxxxxxxx
Los Angeles, CA, USA
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