The Sunday BIRD Volume 8, Issue 21. November 11, 2012

Hi Richard,
I had a good look at my EC-20 and can see no hint of any discoloration. As for the sharpness, I agree that it's a tad softer then the EC-14, but nothing like what you describe.

When used on my ZD150mm as 300mm f/4 I really have to look closely to see much difference to the ZD300mm. Even with the ZD150 wide open I get tack-sharp pictures.

On the ZD300 however working at 600mm the IQ limitation (for me anyway) is motion blur. Perhaps if I get better at handling the ZD300mm  I will begin to notice IQ limitation of the EC-20, but not so far.

I'm thinking that maybe you have a bad copy of the EC-20.  I bought mine in 2011

Peter