F3.4 is a very good lens when one talks about corner to corner sharpness, low distortion and compact size. I loved it when I owned it.
Here is a sample shot on 21mm SEM:
L1000865-1 by
sillbeers15
However it cannot give you the ability to shoot shallow depth of field like below shot by a 21mm Summilux ASPH:
L1006663-1 by
sillbeers15