Yashica DSB 28mm f2.8

     Yashica lenses in the Yashica/Contax era were made by Tomioka and the occasional Cosina.  While the ML line is generally superior to the DSB line, the DSB's can be good performers.  This lens is all metal and glass except for the rubber focus ring.  It focuses down to 11 inches and has a focus throw of 1/2 turn.  The aperture ring clicks at full stops from f2.8 to f16.  Focus dampening is much like a Yashinon lens;  smooth with medium resistance.  It handles well on the full frame 6D.  Focusing is always a chore with a manual focus 28mm lens on a D-slr, though.  At f2.8 it is reasonably sharp.  Corners fall off steeply and there is a typical vignetting.  At f4 it become much better across the frame.  Corners tighten up and vignetting fades.  Edge sharpness is excellent at all apertures.  There is a significant amount of barrel distortion which is strongest at f2.8.   Color rendition is neutral.  Contrast is quite good at all settings.  Side lighting is handled quite well.  I didn't see any loss of contrast or flaring in strong side light.  Bokeh is not silky smooth but not overly distracting either.  Bokeh fringing tests show a slight color shift but it is gone by f5.6 and contrast is excellent.  This is a very good student lens.   Shoot landscapes at f8 on film or full frame and use it as a standard lens on a sub frame D-slr.  It should also produce excellent close ups when used with extension tubes or a bellows on a sub frame body.