[luckystar1992]

即係我影近野,
個光圈都可以係F.2.8-3.5等等.
但係影遠野,
個光圈一定唔比落番去F2.8等等的.
Why??
Thanks!

[dinlo]

因為你嗰支唔係恆光鏡.市面上係有一啲恆光鏡.無論焦距幾多.光圈都不變.

不過就貴少少.

Example:
Canon EF 70-200 f/2.8L
Canon EF 70-200 f/4L

如果你見到係得一個Number, (f/2.8) 就係恆光鏡. 如果係兩組Number (f/4-5.6),就唔係啦.

[luckystar1992]

Thanks先!^^
咁點解要係「恆光鏡」先有咁功能?
莫非制作比一般鏡頭更精密?
Thanks.

[dinlo]

其實"恆光鏡"意思就係"恆定光圈鏡".

當然比一般鏡頭更精密,價錢比較貴.

[man1492]

For a lens with fixed diameter, increasing focal length = decreasing aperture size.

[Gowest]

簡單d講因為恆光鏡既鏡片製作技術要求同成本相對較高,一來鏡組多d,二來鏡片直徑大d打磨工序要仔細d

[Space Walker]

<<For a lens with fixed diameter, increasing focal length = decreasing aperture size.>>

I have query about this statement.

e.g.1 - 恆定光圈鏡 70-200mm f2.8
at 70mm focal length: aperture size = 70 / 2.8 = 25mm dia.
at 200mm focal length: aperture size = 200 / 2.8 = 71.43mm dia.

恆光鏡 doesn't mean the aperture size is fixed throughout the entire focal length range.

e.g.2 - 24-85mm f2.8-4
at 24mm focal length: aperture size = 24 / 2.8 = 8.57mm dia.
at 85mm focal length: aperture size = 85 / 4 = 21.25mm dia.

In this case, increasing focal length = increasing aperture size

Please let me know if I am wrong.

[d2c]

會員戶口已被刪除，資料已被標示為不顯示

[kylee720]

i still love my prosumer olympus C-4000

it have fixed f2.8 for whole range 32-96mm.

[karlm]

光圈的意思係指有幾多光通過支鏡的單位~
當你zoom到最盡個陣d光會係鏡內會令到少左光通過支鏡
(因為鏡片間的折射等等光學因素
令到光係鏡筒內減反射回去
或者係鏡筒間不繼折射
因而令能通過支鏡的光減少)

[karlm]

表?能力比較差~敬請原諒~

P.S.好多術語都唔記得~係大學讀左一年Phy學的野都幾有用~不過宜家無讀生疏晒~

[Cosplay]

唔單只長鏡會係咁，就連影MACRO的時候，
都會因為失光，令光圈收細。

[d2c]

會員戶口已被刪除，資料已被標示為不顯示

[six_seven]

zoom鏡zoom盡時,光圈比例,同實際失光同樣發生!