A pinhole camera is an extremely simple form of camera, which has no lens, and a very small aperture (hole or opening). In simple terms, it is a light proof box with a small hole on one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box. Cameras using small apertures, and the human eye in bright light both act like a pinhole camera.
The smaller the size of the hole, the sharper the image will be, but the dimmer the projected image will be. A common use for pinhole cameras is capturing the movement of the sun over a long period of time, this is called Solargraphy.
Pinhole cameras are usually handmade and made for a particular purpose. In its simplest form, the pinhole camera consists of a light-tight box with a pinhole on one end and a piece of photographic paper taped into the other end. A flap of cardboard is usually used as a shutter. The pinhole is usually punched or drilled using a sewing needle or small diameter bit through a piece of tinfoil or thin aluminum or brass sheet. This is then taped to the inside of thebox behind a hole cut through the box.
The f-number of the camera may be calculated by dividing the distance from the pinhole to the imaging plane (the focal length) by the diameter of the pinhole.
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