There is a proviso though. You need good light for starters as you are stuck with f8. In my example the 2.0 has the advantage of being side on too because depth of field does play a part in critical sharpness. The other factor is the more you lengthen the distance of your lens by using a TC, the more that motion comes in to play. You need a very steady base as all movement is exaggerated. I think a tripod is probably best practice.
As I mentioned in a previous post though one of the big drawbacks is the limited focus points, particularly for trying to get flight shots.
My final two pictures are a rough idea of what sort of final image you might want out of the original shots I took.
There isn't a lot to call between the two really.
Another thing to consider as well is that the long the reach you have the more distortion in the image because of heat haze so again, it's all about distance to the subject and it's size.
And a final thought, of course these examples are on a 500mm f4 lens. It would be a different set of criteria on a faster f2.8 lens,
Hopefully though, although not exactly highly scientific, I might have helped anyone decide on whether or not to buy a 2.0xTC. Now the one thing I'm still not totally convinced about is if the MK111 is any better than the MK11. Sadly I no longer have both to compare.
