i like your website is really usefull your

" concepts " are clear and easy to understand

support and highly appreciate

thanks

控制光圈的大小就可以控制入光量，而光圈值係以 f/xx 來表示，分母 xx 越細，光圈值就越大；分母 xx 越大，光圈值就越細。但大多數人都習慣只講 xx，所以 1.4, 1.8, 2, 2.8 就係大光圈，而 11, 16, 22 就會被稱為細光圈。

因著鏡片物料及鏡頭構造等的原因所限，每一支定焦鏡都有一個最大光圈值，如 50mm f/1.8，它的最大光圈值就係 1.8; 而變焦鏡就因著它的多焦段而可能係不同的焦段有不同的最大光圈值（所以恒定光圈的鏡頭好貴），如 EF-S 18-55mm f/3.5-5.6 IS ，它係焦距 18mm 時的最大光圈值就係 3.5，係焦距 55mm 時的最大光圈值就係 5.6。

關於"大光圈能做成淺景深而小光圈能做成深景深"，請參考”光圈與景深的關係”（http://www.fotobeginner.com/126/aperture-and-depth-of-field/）

As a beginner of DSRL, those info you have given are very useful and practical.

I did reserched lots of other websites giving out the like info, just cannot be understood easily like yours.

Thanks a lot!
Allan Cheung