[tl9078]

如果我有兩支鏡 F2.8 及 F3.5 在同一時間用同一樣的相機拍照是不是用A mode會快門差一級或更多呢？

例如

F2.8 - 1/100
F3.5 - 1/120 etc.....

or 多幾級

F2.8 - 1/100
F3.5 - 1/180 etc.....

[kingkonghk]

點解唔自己試?

向住同一個主體, 相同光源, 插支f 2.8用a mode, 記低快門, 再扭去f3.5, 又再記低佢, 豬魚柿女....

仲有係 f 數字越細, 快門越快先o岩, 你o個d怪怪地

[tl9078]

因為無咁多支鏡囉！

[tyuen]

You can do that with a single lens...

[tl9078]

就係我支係3.5 only！

[tl9078]

學術性問題而且。即係我想起就問，可能好多人都唔知呢？

我又想轉F2.8但想知多D呢！對這些清楚都對攝影有多少幫助呢！

[tyuen]

Ok.

From f/2.8 to f/3.5, it is less than 1 stop (一級).

It is about 1 stop when f number x 1.4. Then one stop smaller from f/2.8 is "2.8" x 1.4 which is about "4".

[tyuen]

f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f11, f/16, f/22, f/32

They are in the sequence of one stop.

[tl9078]

好勁呀。真係好學術性呀。

講真的真的多謝你解答，亦可以多D新人了解多一點。

[tyuen]

Since you use such as serious term as 學術性, I should be more exact...

The factor "1.4" I used is just a rough figure. It should be square root of 2.