Yashica DSB 50mm f1.9

     The Yashica DSB 50mm f1.9 is essentially a Yashinon DS with a C/Y mount.   It looks, operates and images like a DS lens.   

I tried to make this lens take a bad pic.  I couldn't do it.   Whle I am sure the Yashica ML 50mm's have better corner sharpness it wouldn't stop me from grabbing this lens to shoot with.  It is sharp at f1.9. and I mean sharp.  At f5.6 it is razor sharp.  Not only is it sharp but the bokeh is very smooth.  It is pleasing past f5.6.  Fringing is practically non existent.   Bokeh fringing is practically nonexistent.   Flare is well controlled.  You'll need to shoot directly into sun to get a small spot of flare in the corner of the frame.  I didn't notice any loss of contrast due to flare, either.  Ahh yes, contrast.  At f1.9 it is just a tad soft.  From f2.8 up it is excellent.  Shadow detail is excellent and highlight clipping is well controlled.  I had trouble finding a weakness in this lens.  It renders in black and white very well.  The build quality is excellent.  It is a single coated lens and that should mean it is prone to abberations, especially on a digital body, but I didnt see that at all. After bokeh testing I can safely say it will do well in close focus situations.  Color shifts are minimal.  I did not test on a full frame body but I can only imagine that this lens would perform better on a full frame.   I plan to find out.