f/4已經好sharp，從來沒有周邊都好SHARP的ultrawide angle lens,
up to now, I only know 2 lens are sharp at edge,
1. Canon 11-24 f4.0L USM, and
2. Canon 16-35 f4.0L IS USM
最外zoom, 遮光罩仍能保護最出鏡片, 所以可以靠著窗口拍照.
其實Canon 16-35mm f4.0L IS USM 更好用, 和平很多.差不多一支買三支.
However, if you do need 11 to 15mm then this is the only choice.
To me, honestly I don't need this lens, but sigh... it might be make me happier, if I have this lens in my collection.
Anyway, I test it on Canon 5dsR for both 11-24 and 16-35 and the following has some conclusion.
Canon 11-24mm f4.0L USM test alone on 5dsR for my personal judgement
@11mm is ok
@12mm to 18mm very sharp
@20mm is sharp
@24mm is ok
Compare to Canon 16-35mm f4.0L IS USM
@ 16mm, 11-24 is sharper than 16-35
@ 20mm, both lens about the same sharpness
@24mm, 16-35 is sharper than 11-24
I did try Canon 16-35 f2.8, Canon 14mm, Canon 8-15mm, and others lens.
The best result go to
1. Canon 16-35mm f4.0L IS USM- this will be my next collection.
2. Canon 11-24mm f4.0L USM
3. Canon 8-15mm f4.0L USM
In my humble personal opinion, I don't think the other canon ultrawide zoom lens are good enough for 5dsR to use. If you are using 5dsR, try only these three zoom lens. I will talk about prime lens later, I need to go to sleep first. Still need to work tomorrow to earn me enough money to buy my future collection. hehe.... stupid me.