The camera obscura is a old, old project which illuminates the nature of light. Students can discover some major scientific principles: light travels in straight lines, transparent surfaces allow light to travel through while translucent surfaces let some light through, the principles behind photography, scale, proportion and a whole host of other things.
Essentially, a camera obscura is a black box with a very small hole piercing one wall. This hole allows a small amount of light to enter the box.
Now here’s where it gets funky. We need to know two rules about light to understand what happens next. First, light travels in a straight line. Second, light reflects off all objects – it’s the reflected light which our eyes process into visual images. So what happens if light is made to travel through a extremely small space?
Well, the hole focuses the light. When the light emerges from the hole, it spreads out. If you place a white piece of paper or screen on one end of the box, the spread out light will project an image onto the screen. This same process occurs when light enters your eye or camera, except a lens focuses the light in a more controlled manner.
Camera obscuras are relatively simple constructions: a box, a hole, a viewing screen. In my exploration this spring with my students, we made three basic types of camera obscuras. We made the simplest cameras from cardboard boxes. You can find great instructions at www.pinholephotography.org. We found the best designs looked something like this:
Our second attempt was towards a camera obscura which mimics the aesthetic of a Civil War-era studip camera. We built a wood box from plywood scraps, then made a pinhole and screen, much like in the cardboard boxes. We added some heavy black fabric to serve as light blocker. A 1/4-coarse threaded nut glued into a chiseled out recess on the bottom allows the camera to be attached to any standard tripod.
These little projects are fun, engaging and really, really customizable. Students can decorate, modify and tinker to their hearts delight. You can even create a camera obscura which encompasses an entire room (check out great instructions at www.howtoons.com). In the video below, I review some of the physics of a camera obscura and discuss how they work.
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