English Dictionary

focal length

名詞

(optics) A measure of how strongly an optical system converges or diverges light, the inverse of optical power. In the simple case of a single convex lens, it is the distance along the optical axis from the principal plane of the lens to the lens's focal point (where, for instance, the film would be placed in a camera). For more complex or multi-element optical systems, focal length need not correspond to any obvious measurable physical distance.

日本語の意味

光学系において光がどれだけ集光または拡散されるかの尺度を示す値。単一の凸レンズの場合、主面から焦点（例えばカメラのフィルムが位置する点）までの距離となり、複雑な光学系では必ずしも目に見える物理的距離に対応しない場合がある。

To capture distant subjects more clearly, photographers often increase the focal length of their lenses.

遠くの被写体をよりはっきり捉えるために、写真家はしばしばレンズの焦点距離を長くします。

意味（1）

(optics) A measure of how strongly an optical system converges or diverges light, the inverse of optical power. In the simple case of a single convex lens, it is the distance along the optical axis from the principal plane of the lens to the lens's focal point (where, for instance, the film would be placed in a camera). For more complex or multi-element optical systems, focal length need not correspond to any obvious measurable physical distance.

focal lengths （ plural ）