[keanejack]

想請問吓, 50mm F2 景深係咪真係等於 100mm F4。

[Obi-Wan]

try it yourself
http://www.tawbaware.com/maxlyons/calc.htm

[keanejack]

Thanks Obi-Wan. But what is "Circle of confusion".

[Obi-Wan]

Circle of confusion is something related to u have to define it as "sharp" or "blur"

From wiki

"The depth of field is the region where the size of the circle of confusion is less than the resolution of the human eye (or of the display medium). Circles with a diameter less than the circle of confusion will appear to be in focus."

please go http://en.wikipedia.org/wiki/Circle_of_confusion

[keanejack]

Thank you very much! Obi-Wan. 不過好深, 要查吓字典haha. Thank you!

[peterchan04]

噤 用 100mm f4 係想佢 "景深" 淺 定 深....??