Viewfinder

In photography, a viewfinder is a small window the photographer looks through to see what a photo will look like before they capture it. Some viewfinders see directly through the lens, whereas others are separate and show an approximation of what the photo will look like. The second type is much simpler to design, but creates a parallax effect because the viewing angle is slightly different between the finder and the lens. The first type avoids this parallax effect, and is commonly used in SLRs which use a complex mirror system to direct light from the lens to either the film or the viewfinder. Viewfinders are used in many cameras of different types: still and movie, film, analog and digital. Some cameras, such as camera phones and mirrorless cameras, do not have viewfinders and display the image preview on a larger screen. Although, some mirrorless cameras do have a electronic viewfinder, where a small screen shows a video feed from the image sensor. Before the development of microelectronics and electronic display devices, only optical viewfinders existed. Direct viewfinders are essentially miniature Galilean telescopes; the viewer's eye was placed at the back, and the scene viewed through the viewfinder optics. A declining minority of point and shoot cameras use them. Parallax error results from the viewfinder being offset from the lens axis, to point above and usually to one side of the lens. The error varies with distance, being negligible for distant scenes, and very large for close-ups. Viewfinders often show lines to indicate the edge of the region which would be included in the photograph. Some sophisticated 20th century cameras with direct viewfinders had coincidence (split-image) rangefinders, initially with separate windows from the viewfinder, later integrated with it; they were called rangefinder cameras. Cameras with interchangeable lenses had to indicate the field of view of each lens in the viewfinder; more usually, interchangeable viewfinders to match the lenses were used. File:LEI0440 Leica IIIf chrom - Sn.