I am just comparing some lenses and TCs that came to my hand one afternoon. It is interesting to compare an old 400 f/3,5 with the 70-200VR +TC20E (at the same focal length =400mm) to se what a TC does compromising image quality. Even abusing the whole thing (stacking two TCs together) the 400 mm prime still does it better. You can make your conclusions for yourselves. Regards, Miha.