I upgraded my HC 50 for the HC 50 II because the Mk 1 was a bit rubbish at the edges (OK, harsh, but it was not great). The HC 50 II is soooo much better. However I have no problems with the 120mm macro Mk 1, which is my most used lens (on a H4D-50). Sharp, accurate focus, generally a fine lens and good for portaits too. If anyone can post samples showing the difference, I'd be interested.