Viewfinder

an Emil Busch Sellar finder

The viewfinder is an essential part of most cameras for previewing what might be the image after exposure. Only a few camera types are regularly not equipped with viewfinder, for example repro cameras. In digital cameras the viewfinder might be omitted since the LCD display on such a camera's back might serve as provisional viewfinder. It's regularly omitted on big plate cameras which are only used with ground glass focusing/previewing.

In modern cameras the optical zoom viewfinder is the most important version. This modern variant of the optical viewfinder is used in compact cameras with zoom lens.

sketchy illustration of eyeballs viewing through variants of the reflecting type viewfinder

Waist level finders

In antique cameras the reflecting type viewfinder is the most common means of image preview. It is not very reliable but easy to add to a folding camera's front standard or folding bed, or into the housing of a box camera. The brilliant finder is the most widespread of such finders, a combination of a lens, a mirror at a 45 degree angle behind that lens, and another lens at right angle position to the first one to view the mirrored image from the top. An older version was the small cubic Watson finder with lens and mirror as in the brilliant finder, but with a hooded matte screen for viewing the finder image. A special version was the Sellar finder which consisted just of a concave mirror with targeting aid. Old SLR cameras have a bright reflecting type finder with matte screen that uses the same lens as the camera uses for exposures. Before exposure the mirror is lifted so that the light coming from the image subject through the lens can pass towards the image plane where the focal plane shutter allows the exposure of the film for an instant. TLR cameras have a bright reflecting type finder with its own focusable lens, a "twin" of the camera lens, combined with mirror and matte screen. Thus a TLR finder is almost like a camera obscura. All these finders are to be viewed from above. Together they are the class of waist-level finders (or chest-level finders, such names resulting from the height in which a camera is held when the finder is used).

View from above into the large brilliant finder of a Ful-Vue box camera image by on2alan (Image rights)

Telescopic finder with parallax correction knurl image by Uwe Kulick (Image rights)

Eye level finders

Frame finders

Many older cameras have some arrangement of rectangular frames to show the approximate image frame. This might consist of two frames, or one frame with or without crosshairs plus a targeting aid. Some box cameras () had just a single wire frame at the front, with no rear component at all. A big rectangular frame, often of wire, combined with a targeting aid is called a sports finder - following fast action is comparatively easy with this type of finder, where the image is seen at correct scale, correctly oriented, and there is usually some visibility around the edge of the frame. At least as recently as the late 1990s, high-end medium-format cameras were provided with 'sports finders' integrated into the waist-level finder, and a plastic variant of the sports finder can be bought as accessory for modern underwater cameras.

Newton finder

A mixture of a frame finder and frame finder was called a Newton finder, with a single, plano-concave lens in the front frame, and a targeting aid near the user's eye. A disadvantage of this simple design is that users with long sight might struggle to view the scene clearly through the finder's negative lens.

Folding albada finder on an Ensign folder image by Dustin McAmera (Image rights)

View through a bright frame finder with parallax marks below top edge of frame image by Uwe Kulick (Image rights)

Telescopic finders

Other optical viewfinders of old cameras are placed upon the camera top as a small rectangular "telescope". These are often seen in a collapsible form on older cameras, especially folding ones. Since the 1950s these viewfinders were more and more integrated into the camera top housing. Optically, these finders comprise a negative (plano-concave) lens at the front, and a positive lens as the eyepiece (addressing the disadvantage of the Newton's finder above). Galileo designed a telescope which using the same optical arrangement as this finder, in reverse. These finders are therefore sometimes called the "reverse Galilean" type, and they give an image of reduced size. Combining a 'rangefinder spot' into telescopic viewfinders has been common since the mid-1950s.

Albada finders

In some reverse Galilean finders, the concave face of the front lens is half-silvered, to reflect an image of a set of frame-lines, painted on the surround of the eyepiece lens. The user sees the framelines superimposed upon the scene. This type is known as an albada viewfinder (from alba meaning white, the framelines usually being white). This method worked less well when viewfinders began to be fully enclosed (the Pax Jr has an enclosed albada finder, which is very large, perhaps in order to admit enough light to illuminate the framelines). Bright frame (or brightline) finders (below) were the solution to this problem.

Bright frame finders

In many cameras, a bright frame is shown in a telescopic viewfinder by placing a half-silvered mirror in the finder, at an angle to reflect the frames, which are illuminated by light from a translucent panel on the camera front, next to the viewfinder.

Parallax correction

Correction of Parallax error with telescopic viewfinders has been attempted in several ways. Perhaps the simplest is an alternative set of framelines in a brightline finder, to be used for close focus; Less commonly (often seen on Balda cameras), the angle of a telescopic finder may be adjustable for close focusing, as pictured above. Accessory Auto-Up' devices to offset the view of the rangefinder/viewfinder were available (for example that mounted on the Konica pictured right).

Konica with 'Auto-Up' accessory for parallax correction image by Dirk HR Spennemann (Image rights)

More advanced telescopic finders

Modern telescopic finders are often rather sophisticated, incorporating a zoom element to reflect this capability on the camera. Since 1960 several kinds of indicators were developed, the first were red/green indicators for correct- or under-enlightenment in the early cameras with selenium-meter controlled exposure. Nowadays a green LED is standard that's on when the autofocus finished focusing. Other information might be mirrored into the viewfinder or shown in an LCD section in the frame around the viewfinder image. In the 1970s and 80s a row of LEDs beside the finder image was common as scale showing the (proposed) shutter speed or a match-needle metering instrument replacement.

SLR Finders

Finders of modern SLR cameras view through the taking lens and are completed with a pentaprism plus ocular or a mirror system plus ocular. With these additions the reflex finders become eye-level finders and enable the photographer to see the image like through a telescopic optical viewfinder, including any effects introduced by the lens itself or added to the lens.

A new type of the viewfinder is a combination of a miniature color LCD screen with an ocular lens. It's often found in compact digital cameras with a very wide zoom range.

Hybrid finders

Of course the inventiveness of camera developers didn't stop with the question "How can we combine the advantages of waist-level and eye-level in one finder?". One answer was a collapsible hybrid viewfinder. It had a front lens with crosshairs as a targeting aid, what was called Newton finder 100 years ago. With this combination it was an eye level finder. But when its crosshaired mirror was put in at a 45 degree position behind the lens it became a smart waist level finder. Smart because the crosshairs of the lens and that on the mirror helped to find the perfect perpendicular viewing position of the eye over the finder.

An hybrid finder, collapsed, as "Newton finder", and as reflecting type finder image by Uwe Kulick (Image rights)

Glossary Terms