OHP as a commonplace large format camera.

KVANT@nbivax.nbi.dk
Tue, 18 Apr 1995 14:17:11 +0200



A commonplace large format camera -- The overhead projector.

I just learned from the FAQ that a major incentive to use pinhole-cameras
is the need for a cheap large format camera to produce negatives for
gum-bi or other printing techniques.

Note that such cameras are actually *scattered* all over any educational
institution in the form of OHP's

A OHP can be turned into a camera in less time than it takes to expose a
pinhole-image:

You will need:
- a few sheets of black cardboard
- two large, black plastic garbage bags.
- strong tape.
- knife & scissors & small cutting board.

A) Make a small box of cardboard that will fit over and can be attached to
the lens and mirrorholder of the OHP.

B) Put one bag into the other. Place the cutting board inside near the
bottom. Cut two 8 cm long cuts in form of an X. Bend the flaps over and
tape the two bags together along the rim of the square opening.

C) Draw the bags over the OHP and tape to the cardboard box.

The camera is now ready.

Accesories:

D) Shutter: Flap of black cardboard over the opening.

E) Diaphragm: Hole cut in cardboard. Placed over the lens.

F) Negative holder: Empty photopaper box. Can be enhanced in many ways.


Use:
- Put your head into the camera and focus on a piece of white cardboard
with the same thickness as the bottom of the negative holder + negative.

- Load and close the negative holder in the darkroom.

- In subdued light: Place the negative holder in the camera. Take off the lid.
pack the bags closely around the holder.

- Expose.

I used a diaphragm with an approx. diameter of 3.5 cm corresponding
roughly to f12. Ilfospeed paper. 2 x 500W lamps 1.5 m from motive.
Exposure time 10-15 sec.

A lot of work need to be done in order to make this a reliable artistic
tool. I used it in an atempt to visualize for my high-school students,
what a camera and a photographic process is .

Note that you can make the black cover so large that you can sit inside
the camera. You will then be able to burn, dodge or manipulate the image
in other ways.

Note that You will have to check whether two layers of plastic is
sufficient to provide adequate darkness in the camera.

Regards

Mads Hammerich
kvant@nbivax.nbi.dk