EF-S 18-55mm f/3.5-5.6 II 鏡頭的f/3.5-5.6點解？

1)原裝鏡的f3.5-5.6係指在18mm焦距時最大光圈為f3.5而去到55mm焦距時最大光圈為f5.6
2)焦距不是做微距既一個因素,而要看放大率,50mm f2.5放大率為1:2即最大放大率為實物一半大,而180 f3.5L放大率為1:1即實物原大,而50mm通常用嚮產品微距攝影,而180L因焦距較長可以將較遠景物拉近,較合適景一Ｄ唔可以行得太近既主體
3)因DSLR的CCD size較傳統菲林細,較普及的為原焦距的1.5-1.6倍即如果18-55mm x1.6=28.8(約29mm)-88mm
4)對焦環連距離刻度是指對焦距離指示,但因現在科技進步,有全自動對焦,有無距離刻度己不重要
5)遠攝=遠懾定焦鏡頭 e.g 100mm,180mm,200mm,300mm,400mm及600mm等焦距為遠攝定焦鏡,而遠攝變焦鏡 e.g 70-200mm,70-300mm 細看通常變焦鏡都有幾多至幾多mm既指示,定焦因為設計較簡單,通常質數較變焦鏡高,而變焦鏡則較方便易用,兩者都有好處

1. it mean, the MAX at 55mm is f5.6 光圈
2. This is the distance... just like why the lens 70~200 f2.8 ... 70mm can at 光圈2.8 and 200mm also at 光圈f2.8 as well... if you want to take photos to bird.. and use Macro lens, I think you may not use 50mm take it... the bird already fly
3. Being Canon 350D is digital format, all the lens put it on and use is, must need to x1.6 distance. that mean, even you use the lens 18-55, but when you use ot on 350D, it will change to 29-88 mm...
4. this is the distance between the focus and your lens... all the lens must have their min distance to take photos, if less than the require, you cannot focus
5. I think you mention as same thing. 變焦 or 定焦 ... some people will buy 變焦 lens, being one lens can use for some of the range. But it you want quality, some people will prefer 定焦 lens... due to the technology, 99% can say, even 70~200mm f2.8 take photos at 200mm f2.8 compare with 200mm 定焦 f2.8, the 定焦 lens photos quality sure will WIN the 變焦.

Hope this help