Making Various Camerae Obscurae

To experiment with the camera obscura principle and to get an understanding of what a camera is and how it works, we were asked to try making our own pinhole camera for Lab 1 of Professor Steve Mann's ECE516: Intelligent Image Processing course at the University of Toronto. I will walk through the process of my few attempts with both failures and successes—the full learning experience. Please look at the attached pdf for the full lab report.

The first attempt - small pinhole camera:

• Supplies:
• cardboard box
• white paper
• aluminum foil
• scissors
• tape

The second attempt - Pringles pinhole camera (edition: "more cleanly & artistically made")

• Supplies:
• Pringles container
• black paper
• electrical tape
• parchment paper
• scissors

The third experiment - big pinhole camera

• Supplies:
• cardboard box
• white paper
• black paper
• aluminum foil
• scissors
• electrical tape

The small camera was made with a 6”L x 6”W x 6”H cardboard box. The inside was lined with thick black

paper with the sides covered by electrical tape to prevent light from seeping through. The side parallel to the side with the hole was covered with white paper. Two holes were made on the other parallel side; one hole was made to fit the lens of a phone camera, and the other hole was covered with aluminum foil with a small hole that was made by poking a needle through it.

This camera was made with a Pringles container, small rectangular box, and parchment paper. The pringles container was cut to split at around two-thirds of its entire length. The longer one was then cut down the side vertically and taped with a smaller diameter, enough to fit inside the other tube. This extendable design allows for the ”zoom-in, zoom-out effect of a camera as the size of the images depends on the distance between the object and the pinhole. The video linked in this report will further demonstrate how this was made.

A magnifying glass acts as a lens, creating a larger aperture for the pinhole camera, allowed for more light in for brighter and potentially clearer images. The magnifying glass concentrated and focused light onto the white screen, improving image brightness and contributing to sharper details compared to a simple pinhole camera. As all the dollar stores were out of regular magnifying glasses, I bought magnifying reading glasses which didn't have a flat frame causing a bit of light to seep through where it was taped.

Through experimental analysis of comparing the small camera and big camera, some things could be observed. In terms of pinhole sizes, generally a smaller pinhole yielded a sharper image. However, if the pinhole size was too small, it also resulted in degradation of image quality. During experimentation, the optimal pinhole size for the large camera was determined based on a tradeoff between the clarity achieved with a smaller aperture and the potential fuzziness as a result of diffraction. The other observation made was that although both the big box and the adjustable box had obviously longer focal lengths, the aperture diameter did not vary proportionally. In general, a longer focal length and a smaller aperture diameter could contribute to more detailed images, although it may be dimmer. Therefore, larger cameras have greater detail and sharpness.

𝑑 = 𝑐√︁𝑓 · 𝜆

where:

• 𝑑: Optimal aperture diameter

• 𝑐 = 2

• 𝑓 : Focal length (distance from aperture to image

plane)

• 𝜆 = 550 nm

Based on these calculations, the optimal hole aperture would be as in the table attached.