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The centre of the diaphragm's aperture coincides with the optical axis of the lens system. Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris. See the articles on aperture and f-number for the photographic effect and system of quantification of varying the opening in the ...
The Quick Bayonet Mount (QBM) is the bayonet mount system for the range of interchangeable lenses fitted to 135 film cameras built by Rollei in Germany and Singapore from 1970 through 1990, including the Rolleiflex SL35, Rolleiflex SL2000F, and Voigtländer VSL series.
The Minolta SR-mount was the bayonet mounting system used in all 35 mm SLR cameras made by Minolta with interchangeable manual focusing lenses. Several iterations of the mounting were produced over the decades, and as a result, the mount itself was sometimes referred to by the name of the corresponding lens generation (f.e. "MC", "MD" or "X-600") instead.
Rotating the plate would bring an appropriate sized hole in front of the lens. All modern lenses use a multi-leaf diaphragm so that at the central intersection of the leaves a more or less circular aperture is formed. Either a manual ring, or an electronic motor controls the angle of the diaphragm leaves and thus the size of the opening.
Minolta SR-mount lenses can be broken into three broad generations with some overlap: [5] Pre-MC (1958): Lenses with manual, preset, and automatic diaphragms, without the meter coupling (MC) tab on the aperture ring to signal the f-stop that was selected to the in-body light meter.
The semi-automatic diaphragm works in the same way, with a small exception: the aperture does not return to fully open until after the photographer winds the film on following the exposure. Other lenses have a manual pre-set or fully manual diaphragm. [3] Super-Canomatic R lenses are equipped with two diaphragm control rings.
The first Minolta SLRs were marketed with SR- model numbers starting from 1958 with the Minolta SR-2, which featured semi-automatic diaphragm operation with Auto-Rokkor lenses: winding the film advance lever opened the diaphragm and cocked the shutter; when the shutter was released, the iris would stop down to the selected aperture.
The Pentamatic featured an automatic stop-down diaphragm (offered only with the Auto Yashinon 50mm/1.8 lens), instant-return mirror, a fixed pentaprism, and a mechanical focal-plane shutter with speeds of 1-1/1000 second, along with additional interchangeable lenses.