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  1. colincurry

    1.4x extender query

    I have the same gear and a mk iii 1.4 tc. Apparently, the mk iii is designed for use (inter alia) with the 100-400 mk ii. It will autofocus at f8 with a centre spot and four focus points. I found it quite good for static objects but I also found it difficult to lock on for BIF. This was...