400 f5.6 vs 100-400 f4.5-5.6

[sedwards]

i finally got some time to play around with my new 400 5.6 but of course the wind was blowing a steady 30mph with gusts up to 50 again today . i decided to play around a little in the house with it and got the afma pretty close to where it needs to be at +4 then i set up a model to compare the 2 lenses. i thought i was getting pretty decent detail in my bird pics with the zoom lens but i can clearly see more detail with the prime when i zoom in on the image . i also noticed there isn't much of an improvement stopping down to f8 with the prime but a very noticeable difference with the zoom stopped down. here are 2 heavily cropped images where you can see the increased detail. its not a huge difference but its better. now if the weather would cooperate a little i might be able to find some critters to try it on .
prime wide open
400 f5.6 @ 5.6 by sedwards679, on Flickr

100-400 @ f8
100-400 @ f8 by sedwards679, on Flickr

[M_Six]

The zoom will be more suited for airshows. I tried the 400 5.6 at an airshow and it was fine for some shots, but forget prop blur with it. With no IS you can't get the speed down to the 1/120sec or lower that you need for a nice prop blur.

[Minerve101]

Very useful comparison. Have you any impression of the 100-400 with the 1.4X ?