[kfting0616]

按住景深制時,光圈(from f18-36) 7角形狀不太規則,一邊較長,一邊較短,其他五邊圴等,這是正常現象嗎?

[kfting0616]

Hi d2c,
Do you mean that this is a common defect for such a range of lenses?

set at f36@135mm, when I look into the lens (from the hood side), the aperture is actually not so small.

[bb1032003]

kfting0616,

You should not use that small apeture, for normal len for ditigal SLR, you should not use apeture smaller than f8 or f11 due to diffraction problem as the image quality smaller than this apeture will start to drop.

Check this out.

http://www.kenrockwell.com/tech/diffraction.htm