I'm new user of DA20-40. Never used zoom lenses before for a long time. I needed to check AF and made correction with K-5IIs. I was surprised a bit.
All my primes don't need any correction. But the correction is small.
I've made many testing photos last days and found that ALL apertures (from f2.8-3.5-4 till f8) at ALL focal ranges are absolutely working for street photo and photos at close and middle distance.
The sharpness after AF correction is phenomenal. It's the level of FA Limited lenses. And I think my DA20-40 is better than DA21, DA40 and DA35.
Even 20@2.8 is rather good at the center and not bad at the corners.
The bokeh is very good. It's zoom with IQ of prime.
As for infinity - I've found that it's better to use apertures from f4 till f5.6.
Maybe, it's specific character of my copy of this zoom. I don't understand.
Explain me, please, is it normal that the best apertures at close distance and at the infinity are different?
P.S. I've put my DA40 at K200D. It looks a bit sharper at K200D.
DA20-40 wins at K-5IIs.