Pinhole Photography

By Amanda Michaels

Student Projects, Phototgraphy

Because of my interest and little experience in photography, I chose pinhole photography as my concentration for my class project. I researched the pinhole camera, and used the little experience I had, to build my own pinhole camera from an oatmeal can. I used this camera to take pictures around campus. Taking and developing pictures with a pinhole camera was something that I had done, but my objective was to take the "negatives" that the camera immediately produced, and find a way to create a "positive" or a print of these negatives. I ended up with great results although not completely perfected.

The pinhole camera is a Camera Obscura or "darkened chamber". Light reflects in straight lines off the subject in all directions. Those rays that pass through the pinhole aperture land on the back of the camera. The distance from the aperture to the focal plane (where the film is placed at the rear of the camera) is called the focal length. As you can see, in Figure 1, the image is upside down and inversed (like a mirror) on the focal plane (velvatina).

Figure 1. Diagram of an image as seen by a pinhole camera.
The negative will show the image upside down and inversed. ·

Pinhole cameras are inexpensive and not difficult to make or operate. They can be made from and closed container, even trash like an oatmeal can (as used in my project).

"Despite its antiquity and apparent simplicity, the pinhole camera offers several advantages over lens optics, particularly when resolution is not especially important. These include

• complete freedom from linear distortion
• depth of field from a few centimeters to infinity
• wide angular field

The imaging device of the pinhole camera is a hole punched through an opaque material. The image of a distant point is simply the shadow of the hole - or rather the shadow of the material around the hole. That is, the image is a bright spot on a dark background. When the hole is large, the image of the distant point is large and displays a diameter equal to that of the pinhole [Fig. 2(a)].

An extended object is a collection of points; its image is therefore a collection of spots. The smaller the spots, the finer the detail that can be discerned in the object. Therefore, in many ways, the best pinhole is the one that produces the smallest image of a point. If we make the pinhole very small in an effort to improve resolution, we will arrive at the situation depicted in Fig. 2(b). Here, the hole is so small that the pattern of light in the film plane is an Airy disk: the Fraunhofer, or farfield, diffraction pattern of the pinhole. In this region, the smaller the hole, the larger the spot. Evidently, the pinhole that gives the smallest spot lies in the region between the geometrical optics region depicted in Fig. 2(a) and the region of farfield diffraction depicted in Fig. 2(b)" (Young).

Figure 2.   Pinhole camera imaging a distant point.  (a) Large pinhole, geometrical optics. (b) Small pinhole, farfield diffraction.°

Background/History

Pinhole photography was not discovered over night. Many early observations and experiments were completed which led to the invention of the pinhole camera. The Chinese philosopher Mo Ti was first man known to record the formation of an inverted image with a pinhole camera. Mo Ti was aware that objects reflect light in all directions, and that rays from the top of an object, when passing through a hole, will produce the lower part of an image. Scholars such as Leonardo da Vinci, Aristotle, the Arabian physicist and mathematician Ibn Al-Haitam, and the Renaissance mathematician and astronomer Paolo Toscanelli conducted many other experiments.

The first picture of camera obscura is apparently a drawing in Gemma Frisius' De Radio Astronomica et Geometrica (1545). Gemma Frisius, an astronomer, had used the pinhole in his darkened room to study the solar eclipse of 1544.

The term camera obscura ("dark room") was coined by Johannes Kepler (1571-1630). Sir David Brewster, a Scottish scientist, was one of the first to make pinhole photographs, in the 1850s. He also coined the very word "pinhole", or "pin-hole" with a hyphen, which he used in his book The Stereoscope, published in 1856.

In 1892 the Swedish dramatist August Strindberg started experimenting with pinhole photography.

Pinhole photography became popular in the 1890s. Commercial pinhole cameras were sold in Europe, the United States and in Japan. Four thousand pinhole cameras ("Photomnibuses") were sold in London alone in 1892.

In the 20th century, mass production of cameras and "new realism" soon left little space for pinhole photography. By the 1930s the technique was hardly remembered, or only used in teaching. Frederick Brehm, at what was later to become the Rochester Institute of Technology, was possibly the first college professor to stress the educational value of the pinhole technique. He also designed the Kodak Pinhole Camera around 1940.

Today many artists and photographers use pinhole cameras. Pinhole photography has filled museums, books, articles, and the World Wide Web.

My original plan was to make two different sized pinhole cameras and to compare the difficulty involved in making and using each camera. After further research, it was brought to my attention that I could create a print, or "positive" of the "negatives" created by the camera, fairly easily. Having worked with pinhole cameras previously to this class and only developing negatives, this appealed to me as an interesting project concentration. I consequently altered my plans and developed this project.

For my concentration I built a pinhole camera and used this camera to take pictures around campus. I wanted to make clear prints of the negatives I was developing, so this required me to determine the perfect exposure time.

To build my pinhole camera I used a 7-inch oatmeal can. Because of my little, but helpful, experience with oatmeal pinhole cameras, and with the use of instructions I found on the Internet, I was able to build my own pinhole camera fairly quickly, inexpensively, and easily. From my research I know that the materials I used are not exactly ideal, but for my purpose the camera was greatly successful.

The Materials I Used Were as Follows:

• a 7 " tall oatmeal can
• an aluminum can
• matte paint
• a tack
• light cardboard
• black plastic electrical tape
• fine sandpaper
• 3 developing trays containing developer, the stop bath (clean water), and a fixer
• a 25 watt light bulb
• a sheet of glass
• resin coated black and white photographic paper

In building my camera, I emptied and cleaned a 7-inch oatmeal can and in the center (vertically) I cut a small, square hole about 1 inch x _ inch. This is the place for the pinhole and shutter (Image 1). I then covered the can inside and out with matte black paint.

Image1. Shows my camera after
I painted it black and cut a
rectangular hole in the center.

After the paint dried, I cut a rectangle about 2 inches x 1 inch from an empty aluminum can. This piece became the "pinhole." I used a tack to drill a hole into the aluminum (see Figure 3) and used very fine sand paper to even the surface, as not to interfere with the image the camera would record. I then placed the aluminum on the inside of the oatmeal can over the hole I had cut in the can's surface.

Figure 3. Here is an example of drilling the pinhole.¨

To make the shutter, I used a thin cardboard box (one that once contained popcorn) and cut it into three strips. Two strips about 1 inch x 7 inches. These strips were for the shutter guide. I then taped these strips to the oatmeal can horizontally centered on either side of the pinhole horizontally. For the actual shutter I cut a thicker piece of cardboard (like that of a file folder or cereal box) about 1 inch x 2 inches. I then used the third strip of the popcorn box (1 inch x 5 inches long) and evenly folded it to make a handle for the shutter, which would also be used to aim the camera (see Figure 4). To secure the cardboard and aluminum, I used electrical tape. The finished camera can be viewed in Image 2.

Figure 4. Here is an example of a shutter.¨

Figure 5. Here is an example of loading the camera.¨

After my camera was completed (see Image 2), the first thing I did was test for light leaks. I accomplished this by loading the camera in the darkroom (placing a piece of film along the back-inside of the camera opposite the pinhole as seen in Figure 5) and then taking the camera outside and letting it sit in the sun for 20 seconds and then returning to the darkroom to develop the film. My objective was to develop a completely white piece of film. This would mean that no light had reached the film. Idid this and ended up with two tests that were gray, made adjustments, and finally ended with a white negative.

The process of developing the film is quite simple. The film is first removed from the camera in the darkroom and placed into a bath of developer. Here the film will sit for approximately 2 minutes will water is gently agitated. Once the 2 minutes have passed, the film is removed and placed in a stop bath (a bath of clean water). The film must stay in this bath for 30 seconds and then placed in a bath of fixer for approximately 1 minute. The final step is to then put the developed film into a bath of water and allow it to sit for 4-5 minutes (see Figure 6.). Once the film is out of the fixer and into the cleaning bath, it is safe to turn on the lights.

I began then to take pictures around campus. All the pictures were taken in about the same weather. There may have been clouds in the sky, but for the most part it was sunny. The first picture I took, I left the shutter opened for 20 seconds. There was an image visible, but was much too dark. I then decreased the exposure time to 15 seconds; the image was more visible, but still too dark. I then tried 5 seconds and the results were very much the same. I finally was able to get a clear negative by reducing the exposure time to 2 seconds, and thus remained the preferred exposure time for the entirety of my project.

I developed a total of ten negatives and from these ten I chose the four clearest from which I wanted to make "positive" prints. The information I found on developing prints (ultranet) suggested that I use a 15watt light bulb to do so. I was only able to find a 25watt light bulb, but I still received the results I had hoped for. The developing process for the positive prints is the same process used in developing the negatives.

To create positive prints I made a sandwich of the negative and a new piece of film. In the darkroom I placed a new piece of film face up on a wooden board. I then "sandwiched" the negative faced down and centered on top of the new film. I covered both of the pieces of film with a piece of glass, and using the exposure time I found so successful outside, I turned on the 25 watt light, which was held about 3 feet away, for 2 seconds (see Figure 7). I then developed the film and found the same exposure time to be successful for the positive prints. I developed four of my best negatives as prints, and from this was able to conclude that I could make positive prints from the negatives I had previously developed.

Observations and Data

While conducted my project, I also studied different qualities of the camera. I began by cutting a small rectangle out of the top right corner of my film before placing it in the camera. This allowed me to better understand the inversion of the image when revealed on the film (Image 3.). I also took pictures of water and in the shade to study the results of reflecting light. I also cut long, almost panoramic, strips of film to see the distortion gained when using a pinhole camera. I found that the 2-second exposure time in a shaded area was too short and the 2 seconds on reflecting water was too long. I also found that the longer strips of film that I cut did indeed distort the image in that it rounded everything including the street.

Image 3. On the right is the picture "negative" I took using the Pinhole camera, and on the left is the positive print. On the negative in the bottom right-hand corner, you can see the rectangle I cut in the film. That cut was originally in the top left corner (when placed in the camera). Here you can also see that the positive print (on the left) is a mirror image of the negative (on the right).

At the end of my project I was able to conclude I was able to develop the negatives I into positive prints successfully. I found the best exposure time for my camera to be 2 seconds, and I was able to understand the use and the basic properties of the pinhole camera.

pinholevisions

ultranet

pinhole

velvatina

Grepstad, Jon. "Pinhole Photography - History, Images, Cameras, Formulas." Pinhole

Jones, Peggy. "Technical Information." Priciples of Pinhole. 26 May 2002

<http://pweb.jps.net/~velvatina/index.htm>.

Woodruff, Stewart Lewis. "Oatmeal Box Pinhole Photography." Oatmeal Box

Young, Matt. "Imaging without Lenses or Mirrors." The Art of Pinhole Photography.