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Extra care should be utilized when taking a camera to the beach. Sand can cling to the lens barrel, again by electrostatic attraction. This may jam the lens mechanism when it tries to close. When at the beach, always inspect the lens barrel prior to closing to ensure that no sand particles are clinging to it (a single grain can jam the camera).
Mirror lock-up must be activated prior to mounting such lenses, and kept in place in order to prevent damage to the lens or camera. This method of operation prevents any use of the SLR viewfinder with the lens. Prior to the development of lenses utilizing the Angénieux retrofocus concept, mirror lock-up was essential to wide-angle SLR photography.
The effect is that for most lenses, the balance between the decreasing aberrations and the increasing diffraction effects of stopping down the lens means that lenses have an optimum aperture for best results, often about three stops closed down from maximum aperture, so for a lens with a maximum aperture of ƒ/2.8, ƒ/8 would be the optimum ...
Focal-plane shutters may also produce image distortion of very fast-moving objects or when panned rapidly, as described in the Rolling shutter article. A large relative difference between a slow wipe speed and a narrow curtain slit results in distortion because one side of the frame is exposed at a noticeably later instant than the other and the object's interim movement is imaged.
For example, for handheld use of a 35 mm camera with a 50 mm normal lens, the closest shutter speed is 1 ⁄ 60 s (closest to "50"), while for a 200 mm lens it is recommended not to choose shutter speeds below 1 ⁄ 200 s. This rule can be augmented with knowledge of the intended application for the photograph, an image intended for significant ...
The f-number N is given by: = where f is the focal length, and D is the diameter of the entrance pupil (effective aperture).It is customary to write f-numbers preceded by "f /", which forms a mathematical expression of the entrance pupil's diameter in terms of f and N. [1]
The lens is attached to the camera by means of a rotating ring which is used to tighten the lens to the camera by friction. [1] Other methods for mounting a lens to a camera include bayonet mount or thread mounts. With breech-lock, the body of the lens does not rotate relative to the camera body, whereas with bayonet or screw mounts, the lens ...
Video cameras do not have this problem, as any malfunction to the sensor will render the entire system useless. The Arri D-20 and D-21 system, however, does have removable lenses and a rotating optical shutter, which means that the CMOS sensor can be exposed in much the same way as a film gate and thus needs to be kept assiduously clean.