Bellows device

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Camera and lens with reversing ring on a bellows device

In photography, a bellows device enables a longitudinally adjustable connection between the lens and the camera . The attachment of the lens connection and the camera connection is moved on a rail. A bellows connects the lens and the camera in a light-tight manner. In conjunction with a slide copier attachment, slides can be reproduced or, if a digital camera is used, digitized.

With some bellows devices (similar to a tilt-and-shift lens ) the image plane can be tilted relative to the lens in order to obtain a greater depth of field (see Scheimpflug's rule ).

The bellows device is used in macro photography . It enables the image distance to be increased considerably, as a result of which the object distance can be reduced and the image scale can be increased. For use on the bellows device, lenses specially designed for close-up and macro shots with a relatively small initial aperture are available. Lenses of magnifiers can also be used very well on a bellows device, as these are optimized for close-up areas with object widths of around 30 to 40 cm.

Bright normal lenses and especially wide-angle lenses often achieve a significantly better image quality if they are attached to the filter thread in the reverse position by means of reversing rings ( retro position ).

Some bellows devices allow the use of some automatic functions between the camera and lens with transmission shafts or double-wire releases , for example closing the aperture before the shutter sequence, and sometimes also the transmission of the set lens aperture value to the camera housing, so that the open aperture measurement can also be performed with the bellows is possible. In the case of mechanical transmission, however, this only works in the "normal position", i.e. with the lens not reversed. Due to the play of the transmission elements, the accuracy of the mechanical transmission also decreases. Camera systems , which transfer all lens functions electrically, enable loss-free transfer functions with appropriately equipped bellows devices, sometimes also in a retro position.

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