Compur closure
The Compur lock is a central lock type . It was primarily built into the lenses of large-format cameras and single and double- lens reflex cameras. The Compur shutter is arranged as a double aperture lamella set behind the actual mounting aperture . The name Compur is an artificial word from the term “compound” used for central locks and the word “clock”, which was intended to indicate the precision of the lock as a mechanism. Compur closures were manufactured by the Friedrich Deckel company in Munich as a further development of the compound closure since 1908.
They were very high quality and comparatively expensive. Compur closures were therefore mostly used in lenses of superior or top quality. In the case of small formats, they are practically meaningless today because of the costs and the maximum shutter speed of approx. In the case of large and medium formats, they are still up-to-date due to their image quality (uniform image field illumination, see below).
Due to the design, the Compur must open and close completely during the desired exposure time. Therefore, there are mechanical limits to the shortness of the possible exposure times. In contrast to this, a focal plane shutter allows significantly shorter exposure times, since here the limits are not determined by the sequence of movements, but only by the width of the exposure slit . The speed of the slotted curtains is not changed with the focal plane shutter, but their distance from one another. Therefore the shortest possible exposure time of the focal plane shutter can be many times lower than that of a Compur shutter. Since the Compur shutter - similar to an iris diaphragm - evenly brightens and darkens the image during the course of the shutter release, its strength lies in the distortion-free imaging of moving objects, which require correspondingly short exposure times to avoid motion blur , because the recording process is completed within the exposure time becomes.
In most cases, exposure times of B (any) over 1 s up to 1/200 s or 1/500 s can be set on the Compur shutters . The shutter speed series depends on the size and type of shutter. All Compur locks have escapement mechanisms, many with forward drives. Simple Compur shutters (which were widespread from 1904 to the end of the 1930s) create 1/300 s in 35mm cameras and 1/250 s in the size for medium format cameras. The Compur-Rapid, manufactured from 1936, enables 1/500 s or 1/400 s. The fully synchronized Syncro-Compur, which has been manufactured since the early 1950s, is very popular.
The Compur fastener often has to be tensioned separately (in the photo the small lever above the "Z").
Individual evidence
- ↑ Company history on the website of Compur Monitors GmbH, Munich, accessed on November 13, 2011
- ↑ Wolfgang Baier: Source representations for the history of photography . 2nd edition, Schirmer / Mosel, Munich 1980, ISBN 3-921375-60-6 , p. 319