光圈值f是相對值=焦距/光圈有效直徑；焦距變長2倍，f 值增加2倍，雖然光圈口徑還是那麽大，但有效進光量低了

來源: 移花接木於 2023-04-01 06:10:29 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

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