Re: Sigma AF 1.4X worth considering?

[Joseph Tainter]

It is good as extenders go, but only compatible with a few lenses. If 
the lens you are thinking of has its rear element right at the back at 
any point during focusing or zooming, it will clash with the front 
element of the extender. It is not compatible, for example, with my FA 
50 f1.7 or FA 77.

Joe