It
should be fairly easy to manufacture a lens board
using the information and dimensions given above.
Materials
The
original material is no longer available as
production ceased several years ago.
Lens
boards should be a tight (thickness) fit in the
front of the camera. There should be no gaps
around edges.
Whatever
material you decide to use it is important to
ensure it is 100% light proof. An attractive
material to use would seem to be brown electrical
insulating board [Trade name - Paxolin]. However
this is not light proof in thin sheets, letting
red and infra red light.
If
this material is used it is possible to make it
light proof by using thin sheets layered together
with aluminium foil between. Mill the edge of the
panel to the specified width and thickness. Do
not mill through any layers of foil.
Another
material that can be tried is copper coated
printed circuit board. Some boards are coated one
side only whilst others are coated both sides.
U.K. suppliers of this material and Paxolin
include R.S.Components Ltd. of Corby and Maplin Electronics Ltd. of Southend -
on -Sea. Both have websites.
Finishing & Testing
Fitting
a lens sometimes requires a circular step to be
milled into the inside surface of the board to
accomodate the lens fixing ring. The depth of any
milling will depend on the specific lens. The
inside surface of the board is the edge steps
side.
All
bright surfaces must be finished matt black.
Test
for light tightness by leaving a sheet of film in
a double dark slide, lens shutter closed and
front of camera facing the sun or another source
of strong light. Pull the dark slide part way
only. If not light tight, when the film is
developed it will be fogged. Any fogging will
show only on the uncovered area.
If
colour negative film is used to test Paxolin lens
boards any fogging will appear cyan. Colour
transparency film will show red/brown fog.
