Camera Obscura
Watch light rays stream through a pinhole to form an inverted image on the opposite wall. Adjust the aperture size to explore the fundamental tradeoff between sharpness and brightness — the same physics that governs every camera ever made.
About this experiment
The camera obscura — Latin for "dark chamber" — is one of the oldest optical devices in human history. The Chinese philosopher Mozi described the principle in the 5th century BC, noting that light passing through a small hole into a darkened room produces an inverted image of outside objects on the far wall. Aristotle observed the same phenomenon with sunlight filtering through tree leaves during a solar eclipse around 330 BC. Arab polymath Ibn al-Haytham (Alhazen) gave the first clear scientific explanation in his landmark Book of Optics around 1011 AD, establishing the rectilinear propagation of light.
The critical insight this simulation reveals is the pinhole size tradeoff. A smaller aperture produces a sharper image because each point on the scene maps to a smaller circle on the projection surface — but it also lets through less light, making the image dimmer. A larger aperture admits more light but each source point fans out into a larger disc, blurring the image. This is exactly the same tradeoff photographers navigate when choosing an f-stop: smaller apertures yield greater depth of field and sharpness at the cost of exposure time.
During the Renaissance, artists including Vermeer and Canaletto are believed to have used camera obscuras as drawing aids to achieve their remarkably accurate perspective. The device evolved from room-sized installations to portable boxes, and eventually, when a light-sensitive plate replaced the projection screen, the camera obscura became the photographic camera. Your own eye works on the same principle: the pupil is the aperture, the lens sharpens the image, and the retina is the projection surface — and yes, the image on your retina is upside down. Your brain flips it for you.