Viewfinder
A viewfinder is a device of an optical device, such as a telescope or camera , for aiming at an object or subject .
Types of seekers
The simplest viewfinders consist of a diopter with two edges that need to be brought into line, a frame , a crosshair or a reticle .
When using lenses in a Newtonian viewfinder, the inversion of the Galilean telescope , the result is usually a circular, blurred viewfinder image. If a bright-line frame is faded into the viewfinder, which represents the image border, one speaks of a bright-frame viewfinder or, according to the Dutch optician Lieuwe Evert Willem van Albada, of an Albada viewfinder.
Elaborate viewfinder systems use combinations of several lenses, prisms , mirrors or focusing screens . With such systems, if necessary, parallax can be avoided and high accuracy can be achieved.
Electronic viewfinders create a virtual image of an electronic display using a lens system .
Seeker in Astronomy
In astronomy, a finder is a small telescope with a wide field of view that is used to align a larger astronomical telescope. If the axes of both instruments are exactly parallel to each other, the viewfinder makes it easier to find celestial objects, which would be difficult in the large instrument because of its narrow field of view. If you point the viewfinder precisely at the star you are looking for, it will also be in the field of view of the larger telescope ⇒ see finder scope .
Viewfinder in photography
In photography , a viewfinder is a device on the camera or film camera with which a subject can be aimed and the image section can be determined. To adjust the viewfinder to the photographer's visual acuity, diopter compensation can often be carried out. Depending on the equipment of the camera, the photographic viewfinder can also be used to control the sharpness and the exposure time .
In photography, a distinction can be made between the following types of viewfinder:
- Supervision viewfinder - View from the top of the focusing screen of the viewfinder (shooting from abdominal perspective possible)
- See -through viewfinder - look through the viewfinder, which is located directly in front of the eye
- Screen - immediate visual viewing with the eye
Electronic optical devices
The following types of viewfinder are used in digital cameras , camcorders and other mostly digital optical devices:
- EVF ( Electronic View Finder - EVF) - partially pivotally
- Screen , such as a liquid crystal screen or with organic light-emitting diodes , partially rotatable and / or pivotable
Single lens reflex cameras
With SLR cameras , a distinction is made between:
- Light shaft finder - reversed viewfinder image
- Pentaprism finder - laterally correct viewfinder image
- Porro mirror viewfinder (also Porro prism) - the right side viewfinder image
- Interchangeable viewfinder - for cameras that support different viewfinder types
Viewfinder cameras
With viewfinder cameras a distinction is made between:
- Bright line viewfinder
- Rangefinder with the possibility of distance adjustment
Boxing cameras
In box cameras , various assembly and inspection seekers were in use, including:
- Frame finder
- Mirror viewfinder with focusing screen ( flat viewfinder )
- Brilliant finder with converging lenses
- Wire mesh viewfinder (example: various EHO boxes from Emil Hofert )
- Visually viewfinder or riflescope review viewfinder ( Newton-finder or telescope viewfinder ) (example: EHO Altissa from 1935)