How it works - Tincan

~ Single Pinhole ~

Fundamental Law: Light travels in a straight line

We saw how this works by viewing the basic pinhole camera, the wide angle vs telephoto camera and the closeup camera.

The tincan camera uses these factors to produce a purposely distorted image.

Let's look at the tincan camera from the top this time instead of from the side:

As we can see the light rays tracing into the camera are different than our normal camera BECAUSE THE FILM PLANE IS NO LONGER FLAT. To the right or left of center the distance from the pinhole to the film is shorter. Remember that a shorter distance [or focal length] produces a smaller image. If we plot out this effect we get the following:

The center of the camera produces the largest image of the candle and the edges produce the smallest [you did notice that the image is upside down in the previous examples didn't you?].

Here is an actual image taken with a tincan pinhole camera by Steve in the class of 2006:

You can see the the normally straight steps are curved in the way illustrated by the candle drawing. The blurring at the edges is because the can is not infinitely thin and the edges of the can and the photography paper start to block the image from being formed.

Seen from above:

In this exaggerated drawing notice how the closeup aspects play into this as well. The straight on "telephoto" center is nearly macro in how close it is. The edges are wide angle and much further away.

Other classic pinhole cameras, such as the oatmeal box or the 35mm film can work in the same way.