Em,

How much of that fringing is due to the adaptor. Could the adapter be making the fringing from the lens worse?

best regards,
-Greg

Greg,

yes that could be. I know one can´t really see it, but I had a total back-light situation. Quite difficult conditions as it was shady nearly all the time and we had to wait for a second where the sun came through.
I´ll be testing out using a lens file as Greg B. suggested at a shoot this week. Will keep you updated if you want. However to me the image doesn´t appear to be much softer than without the adapter. It performs really very well to my eye.

- All the best, Em.