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Adjustable-focus eyeglasses. Adjustable focus eyeglasses are eyeglasses with an adjustable focal length. They compensate for refractive errors (such as presbyopia) by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both. Current bifocals and progressive lenses are static, in that the user has ...
Prism lenses (here unusually thick) are used for pre-operative prism adaptation. Eye care professionals use prism correction as a component of some eyeglass prescriptions.A lens which includes some amount of prism correction will displace the viewed image horizontally, vertically, or a combination of both directions.
Corrective lens. A pair of contact lenses, positioned with the concave side facing upward. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia.
Eyeglass prescription. Using a phoropter to determine a prescription for eyeglasses. An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient.
What set these cameras apart from earlier Pentax ones was the replacement of the M42 "universal" screw-lens mount with a proprietary bayonet mount system, known as the K mount. Still the basis for Pentax lenses and cameras today, the K mount offered greater convenience and enabled the production of faster lenses such as the 50 mm f /1.2. [17]
In Process 1 (1916), a prism beam-splitter behind the camera lens exposed two consecutive frames of a single strip of black-and-white negative film simultaneously, one behind a red filter, the other behind a green filter. Because two frames were being exposed at the same time, the film had to be photographed and projected at twice the normal speed.
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