A pinhole camera has no lens.
A pinhole camera is a camera without a lens. They are commonly built of lightproof boxes and feature a small or large aperture hole. Light passes through the hole and projects an inverted image on the back wall (usually containing a piece of photographic paper) of the light box.
Camera Size
A pinhole camera can be as small as a tin can or as large as a room. The camera must be large enough to accommodate the photographic paper being used. A larger camera requires larger photo paper, which can be expensive. Because of this most hobbyists use smaller reusable homemade cameras. Large pinhole cameras are generally temporary installations designed to take a small number of photos of a specific scene before being torn down. Cameras this large generally require custom-made photo paper, usually made by hand specifically for the event.
Aperture Size
The aperture is the small hole on the camera through which light travels; the smaller the aperture, the less light that comes through. Generally, smaller pinholes produce sharper resolution.
Exposure
The aperture size also affects the time required to expose the photo paper. Pinhole cameras generally rely on the user to manually control exposure. A larger aperture requires less exposure time than a small aperture because it lets in more light. It's possible to calculate exposure time for larger and more precisely built pinhole cameras, but most amateurs just use trial and error on smaller models.
Tags: photo paper, cameras generally, exposure time, photographic paper, pinhole camera, pinhole cameras, small large
