[飯窯]

光圈F值=鏡頭的焦距 / 鏡頭口徑的直徑。

以50mm 定焦為例, 一枝APS-C鏡頭的直徑比FF短, 如果大家光圈值相同, 焦距相同, 口徑的直徑唔係一樣咩? 但事實唔係咁.

一枝apsc鏡頭的光圈值係唔係等同FF鏡頭光圈值?

[Nailimixam]

光圈值= 鏡頭焦距/光圈孔徑

唔係鏡頭口徑的直徑
http://zh.wikipedia.org/wiki/%E5%85%89%E5%9C%88

[kingkonghk]

一枝apsc鏡頭的光圈值係唔係等同FF鏡頭光圈值? <=== 一樣

APSC鏡即係135鏡, 只係成象圈CROP鬼左4邊

[飯窯]

光圈值= 鏡頭焦距/光圈孔徑

唔係鏡頭口徑的直徑
http://zh.wikipedia.org/wiki/%E5%85%89%E5%9C%88
---------------------------------------------------------------------

即是如果大家都係50mm, 同一光圈值, 光圈孔徑應該一樣大小的.
在相同光源相同環境之下, 光圈值的設定係唔係相同?

如果FF 同 APSC 的光圈是同一東西, 一部dc仔的1.8光圈同一部FF相機的1.8光圈又係唔係一樣?

[kingkonghk]

DC仔都唔係135格式, 點一樣?

APC-C係135格式所以先一樣

[Nailimixam]

飯窯兄唔好唔記得仲有multiplier :)

例如APSC 要50mm X 1.5 = 75mm

[Nailimixam]

for your reference
http://blog.dcview.com/article.php?a=AD4HYQVhATcGbg%3D%3D

[飯窯]

APSC鏡即係135鏡, 只係成象圈CROP鬼左4邊
-----------------------------------------------------------

THANK YOU
但我唔理佢是否CROP o左4邊, 假如FF 相機同APSC同一個擺位, 影同一個目標, 光圈係咪一樣呢?

[飯窯]

for your reference
http://blog.dcview.com/article.php?a=AD4HYQVhATcGbg%3D%3D
---------------------------------------

唔該MAX, 資料很有用, 但另外一個問題係光圈設計, 光圈理論上大唔過鏡頭鏡片, 所以鏡片越大, 光圈才可以越大(不是光圈值, 而是光圈的實際大小), 一枝FF鏡頭的1.8光圈比DC仔的1.8鏡頭大得多, 所以吸光能力大得多, 可唔可以咁講呢?

如果正確, APSC在2者之間, 他的1.8光圈又會不會比dc好而比ff差?

[Nailimixam]

>>>光圈理論上大唔過鏡頭鏡片

in theory, it's possible to make a f/0.5 lens on paper(read it long ago, correct me if i am wrong)

in history, the fastest lens i remember is f/0.7

in reality, there is a f/0.95 Noxxxk lens selling for a while (Canon made a 0.95 long ago)

I also heard that the quality of such lens SUCK.....but i have no $ to try and prove that...

[Nailimixam]

飯窯hing did you notice my reply of "multiplier" ?

in a FF which multiplier = 1, 50mm lens f/1 is 50

in a APSC which multiplier = 1.5, 50mm lens = 75mm (35mm eq.)
therefore putting a 50mm f1 lens on a APSC camera will be:

75mm/50= f/1.5

[老叟]

aps-c 都有好幾種,有D要X1.6!!

[kingkonghk]

但我唔理佢是否CROP o左4邊, 假如FF 相機同APSC同一個擺位, 影同一個目標, 光圈係咪一樣呢?
==================

冇錯係, 只係APS冇左4邊, 整體上構圖會唔同左, 中間位係一樣

[Nailimixam]

>>>aps-c 都有好幾種,有D要X1.6!!



the smaller the sensor the higher the crop factor/multiplier

[pongyee]

APSC 的鏡頭，基本設計上是跟FF 一樣的，只是在某些位置上的玻璃縮小了，因為APSC 用不著嘛。