Gotta stop down alot and is damn slow to focus too. I took this combo (1D,tc n bigma) on a work trip to Gorontalo, Sulawesi last month, missed 2 pairs of red knobbed hornbills in flight a distance away,on a bright day with tc on. I was also pushing the range too, because they were a good 150M or more about 70deg up plane away.
My consolation is making out which sub-species of hornbill it was. And cant complain coz i was not prepared for them to appear and had to quickly change lens. Operator fault more than equipment.
What about DGX or even modifying the Canon extender III?Anyone has anything to share please?