How Do Pinhole Cameras Work?
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What Is a Pinhole Camera?
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A pinhole camera is a primitive camera that anyone can make with just a cardboard box. It is also called a camera obscura, or a dark chamber, because the sides of the box are black. This prevents any reflections when light rays enter through the tiny circular hole that is bored into one side of the box. The light exposes the film or fast photographic paper that is fastened to the back of the box. The size of photographic image that results is based on the distance between the pinhole and the film.
Some Details About Pinhole Cameras
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It is very important that the hole in a pinhole camera is a perfect circle. The diameter of the hole should be 1/75 of an inch if it is located 3 to 6 inches from the film. This is because of the way light travels in "rectilinear" paths. Once the light enters the camera box it will create a reverse image on the film. It is also crucial that the camera not move during the time it takes to expose the film. It takes 2 to 4 seconds on a sunny day or 8 to 16 seconds on a cloudy day if you are using 100 speed film.
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What Is the History of Pinhole Cameras?
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The first person to describe the principles behind the pinhole camera was Gemma Frisius in 1545. He used a pinhole camera to watch a solar eclipse. Later, Johannes Kepler used a similar device when he was observing sunspots. The first person to take a photograph using a pinhole camera was Sir David Brewster in 1850. In 1891, Lord Rayleigh published a formula for the diameter of the hole that would produce the clearest images. In 1995, Eric Renner wrote a book to give modern photographers information about pinhole cameras: "Pinhole Photography, Rediscovering a Historic Technique."
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