Petri 28mm f2

     For starters, this lens is a Cosinon.   Cosina has made some good 28mm's for Vivitar and here they've made a good lens for Petri.   

     I'll get right to it.    This lens is reasonably sharp at f2.  Contrast is excellent wide open.    It is not soft.
     Chroma is very well controlled.  Fringing is well controlled.  Flare is also well controlled.   Shooting directly into the sun will cause a loss of contrast and a few heaxagonal spots but flare is non existent with the sun just out of frame.    Harsh lighting results in some highlight clipping.
     On the subframe Eos M3 there is little distortion.
     Color rendition is excellent.   
     Bokeh is smooth and bokeh fringing is barely noticeable in real life shooting.   However, in close focus shooting it can be seen up to f2.8. 
     It focuses down to 8" and is well dampened.

     On the M3 it makes a good walk around lens.  Focusing is easy through the viewfinder and it balances perfectly in the hand.