Extender 1.4 vs 2 III

amfoto1 wrote in post #15048527
If at all possible, get the 300/4 IS...

Then, since you are using a full frame camera you might also want to get the 1.4X (either the Mark II or Mark III, doesn't matter) to use with it.

I will use either my 70-200/2.8 IS Mk I or the 300/4 IS with 1.4X (II)... but I don't use either with 2X. I only use that on 300/2.8 IS and 500/4 IS. Too much IQ loss on the 70-200. Though I understand the 70-200/2.8 IS II with the 2X III is better... some people will use it... others won't

Check for some examples and maybe some discussion of the combo on the Lens Photo Sample Archive subforum.

Thanks for the link.I am going to rent one for a week and see the results.

I apprecite the help....

Why don't you consider the 100-400. I've made many many great shots with this lens. I recently got a 70-200 2.8 IS II, but keep using the 100-400 when I need more reach. The 100-400 is a bit more expensive that a 1.4 + 2.0 TC, but you get more flexibility. Alternatively, you could consider the 400 5.6 I haven't used that one myself, but consistently read that it's very sharp and great value.

Andrew_WOT wrote in post #15055231
I have 1.4 MKII and 2x MKIII, both required some significant MFA tinkering on 7D and 5DMKIII. After adjustment it's all great.
Give it a try if you still have it.

I gave that a try but the softness was not typical of a misfocused shot. It was almost like there was a light coating of Vaseline or something on the lens (or extender), with some weird halo effects in brightly lit shots. I know it was probably a faulty copy but after some thought I feel the 100-400 will serve me better in the long run, though that is unfortunately a much more expensive route.

Like Andrew, I have the 1.4II and 2x III for my 400 2.8. Love the 1.4 and haven't been disappointed with this combo. The 2x is a little different. I find it requires near perfect LL technique and really is only meant to take a close object and make it seem closer - as in, while it provides extra "reach", it does much better with objects a reasonable distance away vs. something much farther away. For example, I have a fire hydrant in my yard that is about 35 yards from my testing site and there is a porta-jon further down the road where a new house is being built. Using the 400 and 2x, pics of the hydrant are more than adequete, not so much with the hydrant.

It has limitations is really what I am saying and I don't find one of those to be making something 100 yards away look like it is 50. Still a nice tool to have in the bag when used correctly.

Rendil wrote in post #15057032
Unless your a real pixel peeper you should be fine, I read that the only real big difference between the 2x mk ii and mk iii was color casting. Sometimes the mk ii can give you hints of greens or blues where the mk iii is better at avoiding this (just what i read).

I realize this is now moot as far as the OP goes, but...
There is a very significant improvement from the 2xII to the 2xIII in focus accuracy and speed - easily enough to justify buying the III over the II. Edge sharpness and contrast are also improved, and it is much better weather sealed.

I consider TC's a matter of convenience. Mostly, I carry around a set in the bag rather than hauling around the 50-500... If I know I need the 50-500, I take it... Otherwise- if I find that I need reach- I use the TC's and if need be, stop it down.