John Pius's Science Fair Project
John Pius's Science Fair Project
"The Pinhole Camera"
Did you know you could take a picture with an oatmeal box?
A coffee can?
A broken camera?
I have done my project on pinhole cameras. To learn more about them I built two pinhole cameras.
What is a pinhole camera?
A pinhole camera is different from a regular camera because it does not use a lens. A pinhole camera takes pictures by using a pinhole-sized APERTURE that lets light into a FILM CHAMBER. A SHUTTER is placed in front of the pinhole.
When you want to take a picture you have to lay the camera on a flat surface (we used a tripod) and take off the shutter so the light makes a reflected image on the film. The amount of time the shutter is off the film is called the EXPOSURE TIME. The exposure time depends on the amount of light. On a bright day the time will be less because there is more light getting in through the pinhole.. On a cloudy day or in a dark place the exposure time will be longer because less light gets in.
A pinhole camera uses only a tiny pinhole aperture because if it was a big hole the film would be ruined by the light.
Drill your pinhole with a sewing needle (I used a #10 sewing machine needle). Do not poke a hole – it will not be exact enough. The pinhole should be made in a thin piece of aluminum like the metal in a pop can.
The bigger the pinhole the less exposure time it needs to make an image.
My Experiments with Pinhole Cameras
CAMERA #1
We used a broken camera (35 mm single lens reflex). We took it apart and removed the lens and the automatic rewind (we left the dial for rewinding the film). We taped the viewfinder back on with hockey tape.
We made a pinhole with a #10 sewing machine needle in a penny-sized circle of aluminum from a pop can. We used a drilling motion to produce the hole. We sanded the aluminum on both sides to smooth it out, then checked the pinhole with the needle again to make sure it was still open. The pinhole we made was approximately 0.5 mm in diameter. We held it up to the light to check its roundness , then glued it to the camera.
We took a piece of cardboard glued to a penny-sized piece of rubber and taped to the camera body to create a shutter.
On March 7th we loaded the camera with 35 mm Fujicolour 100 o.s.i film and took some pictures. Four pictures came out. The rest were overexposed.
We checked the camera for light leaks and plugged the ones we found with caulking and tape. We made a tighter shutter by gluing a penny to the piece of rubber and fitting it tightly to the pinhole.
We used white paint to mark a line on the film dial and the camera, then we measured how many turns it took to move the film forward for the next picture. It took 3/4 of a turn.
On March 8th we shot another role of 100 film. We only got 5 pictures because the film got stuck. We found that the shorter the exposure the better the picture.
We next loaded a roll of 200 o.s.i film and BRACKETED our exposures. That means we took different exposures and the Shortest (0.5 second) was the best.
We changed our pinhole size by making a new pinhole plate and sanding a bump in the metal until it wore through. We estimated that the new hole was approximately 0.4 mm. According to the formula the optimum pinhole size for our camera would be 0.25mm. Formula for aperture size of a pinhole camera: square root of the focal length (distance the pinhole is from the film)/25
On March 9th we shot three more rolls of film.
CAMERA #2
On March 8th we took a Pentex SLR camera and removed the lens.
We took the lens cap and drilled a dime-sized hole in it . Using the same procedure as with the second pinhole in Camera # 1 we made a pinhole plate and pinhole.
We glued the pinhole piece to the lens replacement cap.
Using the formula (square root of the focal length/25) we found that the optimum size for the pinhole was 0.265
(Square root of 44 mm = 6.6 6.6 /25 = 0.265)
We used automatic focus to get a rough estimate of how long to expose the film.
We used the manual F dial to set different exposure times.
We shot 3 rolls of film using this camera on March 8th and 9th.
History of the pinhole camera
The basic principles of the pinhole camera were known in 5th century B.C. China. Chinese observers noticed 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. In the 4th Century B.C Aristotle commented on pinhole image formation in his work. The Arabian physicist and mathematician Alhazen experimented with image formation in the 10th century A.D..
Gemma Frisius, an astronomer, used the pinhole camera in his darkened room to study the solar eclipse of 1544. In the 1620s Johannes Kepler invented a portable "camera obscura". Camera obscuras were used as drawing aids and were soon found in many shapes and sizes.
Pinhole cameras became popular in the 1890s and were sold in Europe, the USA and Japan. They became popular again in the 1970s. Now there are many websites and newsgroups devoted to the pinhole camera.
I would like to thank Sean O’Brien for the use of his Pentex camera, Fred Murphy for driving me to get my films developed, the people at the Dominion 1 Hour film shop for taking an interest in my project and developing my films mostly for free, and, most of all, to my friend Brian Holmes for helping me with this project.
PROJECT QUESTIONS
1. How did I come up with this project idea?
I was looking on the internet and thought it might be an interesting project to try.
2. What did I learn from my project?
I learned about exposure times and how a pinhole camera is different from a regular camera.
3. What was the most interesting part of my project?
The most interesting part was taking the pictures and seeing them after they got developed.
John Pius
Grade 5, St. Bonaventure’s College
St John's Newfoundland
