The One-Pixel Camera

In this lab you will build something that is the most simple and most fundamental kind of sensor, a camera that has only one pixel in its sensor array.

The purpose of this lab is to help you think about, and understand, imaging, image processing, and computer vision in a very fundamental way. In particular, by temporarily (until later labs) removing the complexities of spatial information, your attention will be drawn to contemplate what a camera truly senses, i.e. quantities of light. This fundamental look at light is what led to the invention of HDR.

What is a camera

The word "camera" is an abbreviation of the Latin term "camera obscura" which means "darkroom". "Camera" is Latin for "room", and "obscura" is Latin for "dark". Early cameras were large rooms and people would go inside the camera to see the picture:

Pictures, Wikimedia Commons; article: Camera Obscura

So basically what you'll be building is a camera obscura with a photo detector inside it, i.e. a structured light meter.

Quite simply, you'll be building a box and putting a sensor at one end of the box, and a hole (or a lens) at the other end to let light in. Ideally you'll make your box black. You can use black cardboard to make the box, or you can line it with black cardboard, or paint it black. Be prepared to explain why it should be black (at least on the inside).

Here's one from a student in last year's lab:

The sensor can be a solar cell, or a photocell such as a photoresistor, also known as a LDR (Light-Dependent Resistor), or as a CdS (Cadmium Sulphide) cell. Typical cost around 75 cents. (35 cents in bulk). These are also sold locally on College Street, a short walk from University of Toronto, e.g. at Home Hardware, as well as at Creatron:

Located in the basement of this Home Hardware store:
290 College St, Toronto, ON
(416) 922-1158
349 College St, Toronto, ON
(647) 349 9258
As with all labs, grading is as follows: Specifically, what we'd like to see a camera and a sketch of its sightfield, as illustrated below:

Make your sketch using alternate directions: draw the first line upwards, then the next one downwards, then upwards, etc., as you move toward or away from the camera, in to remove bias.

In summary here's what we want to see: