Reflex Finder

A reflex finder is a

viewfinder In photography, a viewfinder is what the photographer looks through to compose, and, in many cases, to focus the picture. Most viewfinders are separate, and suffer parallax, while the single-lens reflex camera lets the viewfinder use the main ...

system with a mirror placed behind a

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'' ...

. The light passing through the lens is reflected by the mirror to a

focusing screen A focusing screen is a flat translucent material, either a ground glass or Fresnel lens, found in a system camera that allows the user of the camera to preview the framed image in a viewfinder. Often, focusing screens are available in variant ...

, usually

ground glass Ground glass is glass whose surface has been ground to produce a flat but rough ( matte) finish, in which the glass is in small sharp fragments. Ground glass surfaces have many applications, ranging from ornamentation on windows and table glass ...

. The image formed on this ground glass can be observed directly, giving a ''waist-level reflex finder,'' or through a redressing optical device (set of mirrors or prism) for eye-level viewing, giving an ''eye-level reflex finder''. With a reflex finder, you can focus the image on the ground glass and frame your picture at the same time. It is common to find a device on the center of the ground glass to help precise focusing, for example a split-image or a microprism device. Today's reflex cameras usually incorporate autofocusing. Reflex finders are found in: *

Single-lens reflex A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system (hence "reflex" from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured. With twin l ...

(SLR) cameras, with one lens for both viewing and taking the picture * Twin-lens reflex (TLR) cameras, with one lens for viewing and one lens for taking the picture Cameras {{film-tech-stub