A pinhole is a small opening, often very narrow and circular in shape. It can refer to an actual physical hole made by boring a small diameter hole through a material or surface, such as wood, paper, metal, or plastic. The term can also be used metaphorically to describe something that is extremely limited or restricted in scope, scale, or impact. In photography and optics, the term "pinhole" refers to an optical device with a small opening that allows light to pass through while creating a magnified image on the other side of the pinhole. This type of camera uses only one tiny lens (the pinhole) to capture an image, resulting in a unique visual effect and shallow depth of field.