| The center photo
above shows the typical light drop-off problem in a super
wide camera. |
| 625eq: A hand built, fixed
lens, 35 mm wide-angle / wide-image panoramic
camera made from a damaged Stereo Realist camera body and
a 47 mm f8 view camera lens. If
this were a medium format camera it would be 6 x 25 cm.
The Realist's frame and film advance gearing were rebuilt
to accommodate a new enlarged 24 x 102 mm image frame. Three scans are required to load
each 102 mm negative into the computer. According to Ron
Leven of Schneider Optical the 47 mm f8 super
angulon lens has an image circle of 113 mm at f11,
and a 40.5 mm filter thread. After many light
drop-off tests I find this lens to be unusable without
some kind of center filtering, and B&H Photo accepted a
special order for a Heliopan center filter, but they
never delivered. This
project was my most interesting, but it is now
terminated. Rear view added. |
| Job 1--Film Advance:
In a Stereo Realist the film take-up spool pulls the film
through the camera. The film drives a star wheel sprocket
which is shaft connected to a slotted disk cam in the
upper chamber. A cam follower rides on the edge of
the disk and is shaft linked to a spring coil brake
around the shaft of the take-up spool. When the follower
drops into the slot the brake is applied and the film
stops. A reset pushbutton moves the cam follower out of
the slot, releases the brake and allows the film to be
advanced. For stereo format the star wheel makes one turn
per exposure but in the new camera the star wheel makes
2.2 turns. The first job was to separate the star wheel
and cam with gears to get the 2.2 :1 ratio. The star
wheel bearing support was in the image area of the new
camera and had to be removed and a new bracket had to be
created to support the star wheel, gears and a new cam
disk. This required the cam follower to be modified to
align properly with the relocated cam. (The gears and
bearings were scrounged from my junk box as was the items
below.) |
| Job 2--Lens Mount:
I didn't want to do any unnecessary machining so I
decided to use a screw thread focusing technique much
like screwing a lid on a jar. In this case the jar is
from a pressure transducer bought at an aircraft surplus
store and a matching 55 mm threaded lid. The lens is
mounted through the lid creating an assembly that is
compact and easily removed. The jar was shortened and
modified so the front cover could clamp it to the camera.
The lens mount was something to be proud of until I
discovered severe light leaks. Now it is light tight but
kludged. |
| Job 3--Center
Filter: The light drop off at the ends of my
negatives is 2-3 stops, and none of my many hand made
filters were useable. I have been using Picture Publisher software
to correct the light drop off by using a especially
created filter mask. This was satisfactory for a time,
but is not a permanent solution. (See above photos for
before/after comparison.) |
| Job 4--Focus
Calibration: 1/8 turn = 20',
1/4 turn = 10', 1/2 turn = 7',
3/4 turn = 6', 1 turn = 5', 2 turns =
3', 4 turns = 2', 9 turns =
1' and 12 turns = lens fall off. |
| Note:
The viewer lens is from a one shot Kodak pan camera, but
it brackets the image and shows the horizon. When in
doubt, I use the yellow bubble balance. |
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