Definition: Noun: (1) Rate of transfer of energy from one system to another. * Measured in watts in most applications e.g. electricity, motor; in lumens for light-source. (2) Magnification power or increase in apparent size of image given by optical instrument e.g. 8X power of binoculars means object appears 8 times larger; a 500X power microscope objective projects an image 500X larger than the object. (3) Measure of ability of lens to bend light: equal to the reciprocal of focal length. (4) Telephoto ratio: in a telephoto lens design, the ratio between the focal length and the flange focal distance. (5) Verb: to provide a source of energy for a device e.g. 4 NiMH batteries are used to power a digital camera. (6) Adjective: ~ user: advanced or expert user of e.g. software or operating system or one who makes exceptional demands on the system.

Related Terms: dioptre

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