Some cameras have no viewfinder per-se, but instead use a piece of ground glass at the focal plane to focus the image. This type of focusing and viewing system is typically used on so-called large-format cameras (cameras which use film 4x5 inches or larger). In such a camera, before the picture is taken, the ground-glass viewer is inserted in the back of the camera, and the lens opened to its widest aperture. This projects the scene on the ground glass upside down and backwards. The photographer focuses and composes using this projected image, sometimes with the aid of a magnifying glass or loupe. In order to see the image better, a dark cloth is used to block out light, hence the image of the old-time photographer with his head stuck under a large black cloth.
Glossary Terms