[LargeFormat] Large Format SLR

[Richard Knoppow]

----- Original Message ----- 
From: "Jim Hemenway" <Jim@hemenway.com>
To: <largeformat@f32.net>
Sent: Wednesday, February 11, 2004 1:42 AM
Subject: Re: [LargeFormat] Large Format SLR


> Hi Richard:
>
>  > The Graflex shutter is very simple but
>  > is not self capping and is not uniform in exposure.
>  > This last can be quite noticable at higher speeds
>  > and especially when the film in the vertical position.
>
> What is meant by "self-capping".
>
> So far I haven't noticed any non-uniform exposures but
thanks for the
> heads-up.  I've only used it for horizontal shots.
>
> Jim - http://www.hemenway.com
>
>
   Its an analogy to capping a lens. In a 35mm camera the
the shutter is composed of two separate curtains. When the
shutter is re-wound after exposure the two curtains overlap
a bit so that no light is passed. The Graflex shutter has
only a single curtain with several slits of varying widths
in it. When rewinding the shutter the slit is pulled back
over the film plane. In a Graflex camera the mirror acts as
an auxilliary shutter blocking out the light path when the
focal plane shutter is re-wound, but in a Speed Graphic
there is no mirror, so a dark slide must be in place when
re-winding the shutter or the film will be exposed. The
mirror as an auxilliary shutter allows the Graflex to be
used for strobe photography in the studio. The Series-D and
Super-D use a method Graflex called "drop shutter" where the
shutter is set in O (for open) and the mirror set. When the
shutter is tripped the mirror comes up, tripping the shutter
(the shutter is actually tripped by the mirror), the flash
is fired by the contacts at the beginning of the slit, and
the shutter then closed. The actual exposure time is around
1/7th second so it can't be used for flash fill but can be
used in the studio where the ambient light is low enough to
prevent exposure.
  Some more complex FP shutter designs have been used in
large SLR and press cameras, an example is the shutter in
the Zeiss Mirroflex. Busch also made a few press cameras
with a self-capping FP shutter. I have never seen the Busch
design but it was not the simple Graflex type. Evidently
Folmer & Schwing used a more elaborate self capping shutter
in their first cameras but it proved to be unreliable so
they designed the simple shutter used forever after.
Whatever this shutter's shortcomings lack of reliability is
not one of them. They have proven to be extremely reliable
and long lived.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com