| 释义 |
equivalent focal length
equivalent focal length n (General Physics) optics the ratio of the size of an image of a small distant object near the optical axis to the angular distance of the object in radians equivalent focal lengthThe distance measured along the optical axis of the lens from the rear nodal point to the plane of best average definition over the entire field used in a camera. See also focal length.equivalent focal length
equivalent focal length[i′kwiv·ə·lənt ′fō·kəl ‚leŋkth] (optics) The focal length of a thin lens which forms images that most nearly duplicate those of a given compound lens, thick lens, or system of lenses. equivalent focal length
length, equivalent focalIn an optical system composed of more than one lens, it is the linear distance separating the principal focus from the corresponding principal point. It is usually the most important quantity in the specification of an optical system as in objectives, eyepieces, etc. See principal focus; equivalent power.See EFL
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