[kenanet]

鏡頭既mm係點解？

[terenceworld]

今期o既數碼雙周有提過o架.(從主體平面直至透鏡(鏡頭)的距離稱為焦距離,從透鏡(鏡頭)宜至合焦的焦平面之間的距離稱為(焦距),亦即是鏡頭焦點距離的長短.MM就是鏡頭焦點距離的長短^^

[h0001244]

Goto this link, it will be easy for you to understand
http://www.tamron.eu/en/lenses/focal-length-comparison.html

1.) click "close window" at right bottom corner
2.) move the cursor to focal length scale (which is just below the photo), move back and forth with different mm, you will see the difference