A pinhole camera is a camera without a lens. An extremely small hole takes its place, which shoul be in very thin material. An image's light from a scene passes through this single point, and because there is no lens, the image will be clear at all distances from the pinhole. The smaller the hole, the sharper the image, but the more exposure will be required. Also, in order to produce a reasonably clear image, the ratio of the pinhole, or aperture, size to the distance between it and the screen should be 1/100 or less. The shutter of a pinhole camera is usually manually operated because of the lengthy times, and consists of a flap of some light-proof material to cover and uncover the pinhole. Typical exposure times range from 5 seconds to hours and sometimes days.