« on: June 26, 2014, 09:56:41 AM »
Having had both lenses I can categorically confirm that the Mk11 has better IQ, not by much but sufficient for an upgrade. The ability to shoot at f2.8 without loss of quality is much improved upon the Mk1.
Both Mk111 extenders with the Mk11 lens produce excellent results with little loss of quality with the 1.4 extender. Images with the 2x extender are still superb, see other posts in this regard. Quality with this combination beats the Mk1 lens considerably. I would never use the Mk1 lens with a 2x extender but do so all the time with the new Mk11 lens it is that good.
I have had on occasions the use of a Mk1 600mm Canon lens and quite honestly cannot see much of an IQ difference between this combination and that of the Mk2 300mm lens and new 2x extender when used with my Canon 5DMk111 body.
This lens is expensive but given its many uses and versatility well worth every penny.