No worries GMC, we agree, I just wanted to moderate the very negative overtone of your previous post.
Of course extenders are not as good as native primes. But for the hobbyist that will never buy a 400 better than that, having better results/possibilities with extenders are something to take into consideration too. That's all
Sorry if you felt my reply was negative, it usually quite factual which can voice as a bit cold on forums. No offence were intended or implied and i'm quite freindly really. The 400 f5.6L is a very cost consious lens and very capable too. It lacks a close MFD and IS system but optically and from an AF point of view, it's a fantastic lens which often gets over looked.
Just to push the conversation on a bit. The 1.4x TC on the f2.8 II L version is interesting too, it pretty much negates the need for the 300mm f4 LIS. The combo is just as sharp, AF is just as good, it's IS is superior and it zooms too.