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人眼的感光度這部份有些意見, 人眼對於明暗的感光度是靠瞳孔放大與縮小來控制的, 相當於鏡頭的光圈.當光線強的時候, 瞳孔必須縮小, 減少進光量, 才能看清楚景象, 反之, 光線弱時, 則必須放大瞳孔, 增加進光量, 才能看清楚.也就等於是一台固定快門的相機, 如果要正常曝光, 必須靠調整光圈大小, 才辦得到, 所以當光線超過光圈的極限時, 就無法看清楚影像了.光線過強時, 鏡頭就加濾鏡, 或加遮光罩, 相當於帶太陽眼鏡或瞇瞇眼; 但是光線過弱時, 相機是可以藉由延長曝光時間或提高ISO值來補償, 人眼就沒辦法了, 一般人所謂在黑夜看久了也能看清楚, 是因為瞳孔瞬間縮放必須有一定的時間, 並不是延長曝光.原則上人眼的感光度應該也是固定的.
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Reader Comments (Page 1 of 1)
BlackHeart @ Sep 3rd 2008 12:33AM
人眼的感光度這部份有些意見, 人眼對於明暗的感光度是靠瞳孔放大與縮小來控制的, 相當於鏡頭的光圈.
當光線強的時候, 瞳孔必須縮小, 減少進光量, 才能看清楚景象, 反之, 光線弱時, 則必須放大瞳孔, 增加進光量, 才能看清楚.
也就等於是一台固定快門的相機, 如果要正常曝光, 必須靠調整光圈大小, 才辦得到, 所以當光線超過光圈的極限時, 就無法看清楚影像了.
光線過強時, 鏡頭就加濾鏡, 或加遮光罩, 相當於帶太陽眼鏡或瞇瞇眼; 但是光線過弱時, 相機是可以藉由延長曝光時間或提高ISO值來補償, 人眼就沒辦法了, 一般人所謂在黑夜看久了也能看清楚, 是因為瞳孔瞬間縮放必須有一定的時間, 並不是延長曝光.
原則上人眼的感光度應該也是固定的.