[Student Projects, Photography]
Silver Photography with Pinhole Cameras
camera is a relatively simple device to
construct. It consists of a light-safe container (coffee cans or thoroughly
sealed boxes work well) which is painted matte black inside and outfitted
with a pinhole and a shutter. Through this pinhole, light is transmitted
and the image is projected upside-down onto a surface opposite the pinhole.
This projected light is what reacts with the chemicals in the film in order
to create the negative.
Despite the simplicity of the pinhole camera, however, there are certain details which one must take into account in order to get the best possible image: the first is that the camera must be absolutely light-safe. Painting the inside black prevents light from reflecting within the camera and altering the image; however, even the smallest unintentional aperture can let enough light in to ruin the clarity of the image, and cause what photographers refer to as "fogging". The second is the question of pinhole size; most instructions state that a pinhole made by pushing a #10 sewing needle halfway through a piece of aluminum, sanding the rough edges of the hole, and fitting it over a larger hole in the camera container itself yields the best images. The third is the distance of the film from the pinhole; a short distance gives a clear but small image, and a large distance diffuses the light and the image is blurry. I personally found (after some trial and error) that a distance of 8-10 inches between the pinhole and the film works very well. Last, but still very important, is the matter of mounting the film securely within the camera. Despite the fact that I constructed channels into which I could slide the film, there was still some occasional slippage, and some ruined negatives. Taping the film inside the camera (as my colleague Joy Reeves did) is one option; and although the channels were not foolproof, they worked well for the majority of the time.
My own camera consisted of a cardboard box, originally about 20" x 10" x 8" in size, with a standard-size pinhole and a space for the film to be mounted upon the back interior wall (i.e. 20" from the pinhole). My reasoning was that a longer distance would produce a larger image; however, this was soon modified as it would not produce an image upon the negative at all. I modified the camera by cutting, re-folding, and re-sealing the box, and adding a film-loading door on the top of the box so that the film could be slid through the door and onto an internal wall approximately 8-9" from the pinhole. All corners and other possible light openings were thoroughly sealed with black electrical tape.
My Own Experiment with the Pinhole Camera
My experiment involved constructing a pinhole camera in order to accomplish
two things: 1)to try to find the optimum exposure time, lighting conditions,
and so forth for producing the clearest image on a large negative; and
2) to test the effect of colored filters upon the resulting image. The
first part of the experiment ended up focusing more upon the elimination
of unwanted variables--as mentioned above, I had to modify the camera so
that the film would be closer to the pinhole. Furthermore, I could not
seem to get any image at all upon the negative; so, I tried a different
kind of film. After I finally obtained an image upon my negatives, I noticed
the presence of some dark spots obscuring parts of the image, which indicated
that my camera was not entirely light-safe and the film was being exposed
in parts to light. And, of course, I had two situations in which the film
slipped out of place and I lost the image altogether. Once the troubleshooting
was complete, however, the experiment yielded some interesting results.
My first three test strips were Ilford film; as I could not seem to get an image on these, I switched to Kodak. All photographs were taken under the same lighting conditions (bright sunlight, light meter reading of 250).
Test Strip #1: Exposure time-2 seconds. Nothing at all. Be sure to use the right side of the film.
Test Strip #2: Exposure time-4 seconds. Still nothing. Longer exposure time necessary.
Test Strip #3: Exposure time-5 seconds. Completely black. This is the point at which I switch films.
Test Strip #4: Exposure time-1 second. The desired image appears. Slightly longer exposure needed.
Test Strip #5: Exposure time-2 seconds. Better, but blurry. Camera needs to be steadied.
Test Strip #6: Exposure time-2 seconds. Good detail, but could be exposed longer. Film slips out of place, and image disappears halfway down the negative.
Test Strip #7: Exposure time-4 seconds. Darks and lights are well-balanced; good detail.
Test Strip #8: Exposure time-5 seconds. Too dark to be discernible. 4 seconds appears to be the optimum exposure time.
After taking two more pictures to be certain that 4 seconds was the best exposure time, I incorporated cyan, green, and red filters--the last being the most interesting since the Kodak Ortho film I was using was not red-sensitive. My hypothesis was that no image would appear at all with the red filter. All photographs were taken under the same lighting conditions as above, with exposure time of 4 seconds.
Green Filter: Not as much detail--the finished print will be much darker than normal.
Cyan Filter: Better detail than in the original control photograph; shadows and highlights very distinct.
Red Filter: As expected, no image at all. This was attempted three times with no result.
More Information About Pinhole Cameras via the Internet
While there are a number of websites devoted to the art of pinhole photography,
some of them are either easier to get to or more helpful for the amateur.