[lubolubo]

已有支定焦50mm F1.8 同 支變焦18-55mm F/3.5-5.6 IS....

我知"F1.8" 係最大(size)光圈值, 咁F/3.5-5.6係乜???

定焦50mm距離其實幾多??? 成日覺得好近咁... 咁18-55mm 距離又係點???? 咁係5係18-55mm 當中都有50mm嘅"尺度"？？？

再加鏡會5會小小白70-200 F4 IS啱？但$$$!!!

[hkbeer]

咁係5係18-55mm 當中都有50mm嘅"尺度"？？？

Yes

[ZeroJKwok]

mm 指的原則上不是距離，而是視角的闊度，如：50mm，它是最接近人眼視角的46度。 =)

[milk_yu]

另外請問...canon 因為粒CCD既格式唔同..
所以50mm 需要 x 1.6 = 80mm

咁80mm 係代表視角的闊度??!!

[50D]

18-55mm F/3.5-5.6 IS
18mm ....largest aperture is f3.5
55mm... largest aperture is f5.6

[grandlun]

一般用"焦距" 或"焦段" 去形容你所講geh "距離"...跟視角有關, 距離冇關

對焦距離係主體同感光元件之間geh 距離...呢個先跟距離有關

另外x1.6 係因為感光元件size 比正常full frame 細, crop 走左四條邊, 所以相片有效焦距就tele 左...亦可以理解為視角窄左...

[grandlun]

btw...勸樓主先影多D相...
等多D 經驗先慮入多支鏡...
如果你係認為人人都話好geh 小小白IS 貴的話...

咪到時買支L鏡番黎只係當望遠鏡咁用...

當然如果樓主好有錢geh 話...
就買啦~

亦可考慮入支55-250 IS 旁身...

[ZeroJKwok]

80mm ?? 唔知道個視角是多少！ 85mm的約為28度30分 =)

[fallbackskiing]

Might be need to draw a triangle and use tan-1 to get the angle, I guess.
Not very sure, 50mm focal lenght project to 35mm CCD with 135mm full frame size..... very complicate wor!
Check the lens specification might be a faster way to find the corresponding angle, no mathematics!

But it is quite a good reference to have 50mm = certain an angle of view. Easy for me to understand what we need to choose on lens.