I am using a Nikon 200-400 etc etc coupled to a 1.4TC on a Nikon D700 (giving an effective 560mm reach on full zoom) - the results are great when the combo works but I have to say that the coupling between TC, Lens and Camera is troublesome and often gives incorrect readings and poor auto focus. Have had it repaired three times - works well initially but then fails again. It is really heavy too - much heavier than my sony a900 Bigma combo but the quality of the Nikor lens makes all the difference.