Twin-lens reflex camera
A twin-lens reflex camera (English: Twin Lens Reflex, TLR abbreviated ) has two stacked lenses. Above generated deflected via a mirror, the finder image is displayed on the focusing screen, the thereby upright but upside down. The bottom is equipped with a shutter and a diaphragm, and is responsible for the exposure on the film.
Properties
Both lenses are mounted on a common standard and are adjusted together to focus. This allows the viewfinder as single reflex cameras precise adjustment of the focal plane. To provide a bright as possible viewfinder image viewfinder lens is often more light, but here for cost reasons a simpler construction than the taking lens. The viewfinder is mostly implemented as Faltlichtschachtsucher, the TV screen may comprise a Fresnel lens for improved brightness distribution, but usually has no other setting aids. Often a foldable viewfinder is available, which allows a more precise focus, through the often not the entire viewfinder is be surveyed. Some of these viewfinders can be used as a simple frame viewfinder euphemisch sometimes called sports finder.
Twin-lens reflex cameras usually use roll film type 120 or 220 and expose Negative Format 6 × 6 An exception is, for example, the so-called "Baby Rollei " for roll film of type 127 and with an aspect ratio of 4 cm × 4 cm.
Twin-lens reflex cameras have over competing designs on both advantages and disadvantages. The fixed mirror is easier and cheaper than costly oscillating mirror constructions eyed SLR and still allows, in contrast to the viewfinder cameras to assess the focal plane. The lack of mirror mechanism, these cameras are in operation very quiet and operate largely free from vibration. In addition, the viewfinder image remains visible even when the absorption and therefore the photographer at any time full control over the events ( such as when the subject is blinking when recording). With the frequent Lichtschachtsucher the entire viewfinder image can be viewed with both eyes. This simplifies the image composition and also allows an unnoticed photography. Since the viewfinder lens operates independently of the iris setting of the taking lens, or using a lens filter, the viewfinder image is usually always on full brightness. Before the invention of the automatic diaphragm of the viewfinder SLR -eyed when setting the desired aperture value for shooting was darkened accordingly. The design allows for a compact and lightweight design, making it ideal for travel photography.
A disadvantage is the viewfinder parallax, in practice usually is not relevant, however, and is automatically compensated with high-order models. Getting used to the wrong- viewfinder cameras with viewing or prism viewfinder indicate a laterally correct image.
The cost advantage of relatively simple mechanical construction into perspective for models with interchangeable lenses, there are always two lenses are required. Since the two lenses are mounted above each other relatively close, also further restrictions on the possible focal lengths and intensities of the interchangeable lenses give.
History
This type of camera was developed from the Brunswick company Franke & Heidecke, which later got the name Rollei. The Rolleiflex and her sister simpler model Rolleicord were popular cameras for decades for photojournalists. Over the years there were more models of Mamiya ( with interchangeable lenses ), Zeiss, Yashica and many other manufacturers.
While most TLR cameras have disappeared from the market, Rollei continues to offer current models with different focal lengths: the Rolleiflex 2.8 FX with a lens of 80 mm, a 4.0 FT with a telephoto lens with 135 mm focal length and a 4.0 FW with a wide-angle lens with 50 mm focal length. The DHW photo technique, the successor company Franke & Heidecke, presented at photokina 2012 before a new edition of the legendary twin-lens 6 × 6 medium format camera as a Rolleiflex FX -N. There are also technically much simpler and inexpensive models like the the Chinese manufacturer Seagull, or the Russian Lubitel series.
Trivia
The twin-lens reflex cameras with frequent insight into the viewfinder from above results, if not balanced, often derisively referred to a camera pose which give the so -built photos especially when shooting people a typical perspective as abdominal perspective. In high-quality versions such as the Rolleiflex and Mamiya C220/C330 this can be replaced by a prism finder, with the results in a laterally correct and upright image.