With the Sigma extender will it allow full function of Canon lenses and also offer the same weather seals as the Canon counterpart?
I also thought that the Canon extender would work on the 70-200. I need to be able to get to a shop to see things for myself. This is the problem I face living 5-6 hours away from the nearest store stocking Canon.
So I thank you greatly for your advice. Please keep them coming.