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Opera glasses, also known as theater binoculars or Galilean binoculars, are compact, low-power optical magnification devices, usually used at performance events, whose name is derived from traditional use at opera performances. Magnification power below 5× is usually desired in these circumstances in order to minimize image shake and maintain a large enough field of view. A magnification of 3× is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular lorgnettes of the 19th century. The London Opera Glass Company was founded in 1913 and provides opera glasses in many of London's West End theatres. ==See also== * Binoculars * List of telescope types * Lorgnette * Monocular * Spotting scope * Telescope 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「opera glasses」の詳細全文を読む スポンサード リンク
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