| inviato il 20 Aprile 2016 ore 21:04
sono leve per l'accoppiamento dei diaframmi.
mammano progredivano i corpi, le lenti avevano bisogno di sempre più leveraggi.
ai fini di un utilizzo con anelli adattatori il dato è assolutamente ininfluente. |
user39791 | inviato il 20 Aprile 2016 ore 21:08
Grazie. |
| inviato il 20 Aprile 2016 ore 21:12
copio e incollo da un altro sito:
Single-cam lenses (1964-68): Lenses that were released in conjunction with the original Leicaflex had one curved chrome-bar between the mount and the rear lens element to transfer the aperture setting on the lens to the camera. These single-cam lenses (alternative called "one-cam" or "1-cam"-lenses) can be physically mounted on later Leicaflex SL and R-cameras, but the cam does not transmit the aperture setting to the newer cameras, so that only stop-down metering is possible. In other words, the aperture has to be closed down to the intended f-stop for the camera metering to work properly. However, Leica recommends not to use single-cam lenses on the R8 or R9, as heavy usage of the old lenses in the past might have led to a slight misalignment of the cam that could damage electrical contacts in the female part of the mount of the latest SLR cameras.
Twin-cam lenses (1968-76): With the introduction of the Leicaflex SL that supported TTL-metering, Leica changed the lens-to-camera coupling mechanism and moved the curved cam to the opposite side of the lens mount. To nevertheless ensure that the newer lenses could also be used on the original Leicaflex, the first cam was maintained, resulting in twin-cam lenses (alternatively called "two-cam", or "2-cam" lenses). The first cam does not have any function on the Leicaflex SL, but is used to set the viewfinder display of the aperture in the Leicaflex SL2. Similar to single-cam lenses, twin-cam optics can also be used on R-cameras using stop-down metering, but are not recommended in conjunction with the R8 and R9.
Triple-cam lenses (1976-96): The R3, which was developed in cooperation with Minolta, introduced once again a different coupling mechanism. This third cam takes the form of a triple-stepped, black projection at the inside of the second cam. The first and second curved cams were maintained to ensure backward compatibility of the lenses. The resulting "triple-cam"-lenses (alternatively called "three-cam", or "3-cam" lenses) function on any Leica reflex camera in open-aperture mode, and can be used with the R8 and R9.
R-cam lenses (1986-09): Ten years after the Leicaflex SL2 was discontinued, Leica started to produce R-lenses that only had the third, stepped cam, but lacked the first and second cams. These lenses would, hence, not transmit any aperture information to the Leicaflex/SL/SL2 models, and Leica indeed changed the shape of the lens mount slightly, so that these R-cam lenses (alternatively called "R-cam only", "R-only", "three-cam only", or "3-cam only" lenses) could not be mounted on the Leicaflex/SL/SL2.
ROM-lenses (1996-09): The R8 featured electronics that could take advantage of lens-specific information to correct for lens vignetting, to adjust the zoom reflector on flash guns according to lens focal length or to correctly display aperture information if accessories, like tele-extenders, were attached to the lens. This lens-specific information was stored in a Read-Only Memory (ROM) chip that was added in the form of a strip of electrical contacts between the mount and the rear element of R-lenses. The ROM chip came with all newly sold lenses at the time, but could also be retrofitted by Leica technicians to older lenses. ROM-lenses have the R-cam and can also be mounted on R3-R7 cameras, where they support all the functions that these cameras offer. |
user39791 | inviato il 20 Aprile 2016 ore 21:18
 |
Che cosa ne pensi di questo argomento?Vuoi dire la tua? Per partecipare alla discussione iscriviti a JuzaPhoto, è semplice e gratuito!
Non solo: iscrivendoti potrai creare una tua pagina personale, pubblicare foto, ricevere commenti e sfruttare tutte le funzionalità di JuzaPhoto. Con oltre 252000 iscritti, c'è spazio per tutti, dal principiante al professionista. |
Metti la tua pubblicità su JuzaPhoto (info) |
JuzaPhoto contiene link affiliati Amazon ed Ebay e riceve una commissione in caso di acquisto attraverso link affiliati.
