equivalent focal length
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noun
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
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Words nearby equivalent focal length
equivalence relation, equivalency, equivalent, equivalent air speed, equivalent circuit, equivalent focal length, equivalent weight, equivalve, equivocal, equivocally, equivocate
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How to use equivalent focal length in a sentence
The equivalent focal length of a negative or Huygens eyepiece is equal to half the focal length of the larger or field lens.
Pleasures of the telescope|Garrett ServissWhen the simple67 expression "focal length" is used, it always refers to the equivalent focal length.
The Barnet Book of Photography|Various