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Company Seven's Modified Pentax 6x7 Cameras
This Pentax 6x7 camera body has been selected and modified to better meet
the performance criteria for successful astrophotography. Be assured the
factory warranty continues in full force. Also, none of these
modifications precludes the use of any optional Pentax 6x7 accessories,
nor does it preclude the use of this Pentax 6x7 camera for conventional
photography. However, there are certain operational differences between a
standard Pentax 6x7 camera and those which are modified to meet Company
Seven's criteria. Not all of these features are mentioned in the standard
Pentax 6x7 owners manual or listed here, but the most obvious differences
to the user will be:
In order to allow long time exposures at the "B" mode without draining
the battery, this body has been modified to allow the bypass of the
battery. The procedure to activate the shutter is as follows:
- Clear Screen: The standard focusing screen has been replaced with
another in order to facilitate focusing at relatively high f ratios (such
as encountered in macro photography, or with long lenses and telescopes),
or when photographing objects in low light environments.
The focusing screen has been precisely fitted to assure the screen is
parallel to the film plane. The bayonet mount alignment to the film plane
may have also been adjusted as necessary to assure pinpoint imaging
across the film plane.
- Shutter Power Bypass: The standard factory issue Pentax 6x7 camera is
an electronic body. The focal plane shutter mechanism draws power from an
internal 6 volt battery or from an optional external source to activate.
The shutter requires power to maintain an open condition whether the
shutter speed is set to 1/500th of a second or for a long exposure of
many hours. The power requirements drain the battery such that the
battery becomes exhausted after a matter of several hour long exposures.
Also the ambient temperature will affect battery output; this takes on a
more important dimension in a cold environment.
Thank you, and we wish you a lifetime of enjoyment with your
camera. For information about other accessories for your telescope
please call us.
- Perform a battery condition test: press the white plastic button at
the rear of the camera near the shutter speed dial. If the L.E.D. (at the
inboard side of the shutter speed adjustment dial) lights then you may
continue, otherwise replace the battery.
- Insure the camera is loaded with film, then advance the film crank to
the first frame.
- Optional: If the film is to be commercially processed, we suggest the
first frame of film be exposed to light so that commercial laboratory
film cutters may have an indexing point of reference.
- Attach a lens to the camera, or the camera to a telescope. Frame and
focus the object or the area to be photographed. Insure that any focus
lock (such as a drawtube lock screw on a telescope focuser) is set.
- Thread a primary camera cable release into the small socket at the
front panel on the camera body, (below the manual shutter release
button). When installed onto the camera, the primary cable release should
be unlocked (or relaxed) before it is thread into place. Set the
primary cable release selector to "lock"; this will hold the shutter open
when the primary cable release button is depressed.
Set the camera shutter speed adjustment dial to indicate "B".
- Suggested option: Activate the mirror lock up by sliding the momentary
switch (located to the right of the bayonet mount) up. You will hear a
"click", then the focus screen will go black.
- Depress the primary camera cable release button. It should lock in the
- Trigger the camera shutter by gently pressing the shutter release
button. A secondary cable release may be employed to further reduce any
possibility of vibrating the system; if so the secondary cable release
selector should be set at the momentary (as opposed to lock) position.
- To preserve battery life, now remove the battery or disconnect the
optional cold weather battery pack. As long as the primary cable release
is set, the shutter will remain open and the mirror will remain up.
- To end an exposure, gently grasp and then unlock the primary shutter
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