Kobori manufactured this lens for Vivitar. So, is this lens any good? I am testing it on my Eos M3. It is front heavy. It also has the shortest focus throw I have ever seen, but due to excellent dampening, it's not hard to focus. Optically, it is no Kiron, but it can produce nice images. First, avoid f3.5. It is just too soft wide open. Stop down to f5.6 and it tightens up nicely. Quality is consistent from 28mm thru 85mm. Distortion is well controlled. Colors render on the cool side. Fringing can be seen at 100% crop in high contrast lighting but it is minor. Bokeh is a negative with this lens. It's uneven hexagonal iris creates a busy and distracting bokeh. Macro is available at 85mm. Macro performance appears to be very good.
85mm f3.5 and f5.6 - crops