Do u have some pic to show?
I just took these shots. All are ISO 100, at 16mm, taken with a tripod. Taken with 40D. Aperture priority mode. I hope the size is alright.
These were taken without flash

These were taken with flash (580EXII)

Without flash, the sharpness was ok even wide open. With flash, as you can see above, f2.8 was extremely soft and looks like it was out of focus. I did not move the camera or the object, so the focus point is constant throughout the shots. I actually wouldn't really mind since the f2.8 will most likely be my "emergency" aperture of choice lol. The sharpness seems to diminish at f16. I did not try f22. Well, I haven't really had a chance to play with this lens properly, but I don't understand why this lens would behave like this when a flash is used. Is this normal? I've never owned a WA lens before, let alone a UWA lol.
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