No photos to share, just some info on T-Cons and bodies.
I decided to try the 120-300mm with the Canon 2X for 600mm @ f/5.6
I was initially shooting with the 7D2
The results came out pretty good. Definitely useable, some very sharp. AF was not very confident, but again useable. It's a combo I would try in the field if the situation demanded.
This caused to me get a little crazy and try something stupid. Arguably, the lens should AF with any body capable of f/8 AF with BOTH the 2X and 1.4 mounted.
It just so happens that I have 3 bodies that will do that, so I decided to stack them and see how we fared.
The resulting optic is 840mm at the long end f/8 Wide open.
On all three bodies the second T-Con was ignored by exif, it was "non reporting" so in camera the aperture would report as large as f/5.6, but it was not really there. Exif still shows a 600mm. Once I stopped down to f/11 that of course showed in the exif correctly.
Since cameras could not detect that it was f/8 they did not limit me to center AF point only.
The 7D2 did badly. AF would not settle. I tried limiting to center AF point only but this made no difference. It tried, but it just was unusably erratic.
This was a failure IMHO with the far too erratic AF that would no lock.
Next was the 1D4 which I assumed would be the best, because hey, may be old, but so is the lens and T-Cons and well, it's a 1D!
In fact, I saw little to no improvement over the 7D2. Same jittery AF jumping.
Last up, the 5D3.
Surprise surprise, the 5D3 was actually useable! The images were most sharply in focus, and much less jumping around to get there.
I doubt I'd ever stack t-cons with this lens in the field, but with the 5D3 I would consider it a workable solution.
As for the lens itself, I feel that it performed remarkably well optically. Some of the images ended up with a bit of a washed out look, but on the whole stopped down to f/11 (from an actual f/8ish wide open) the image quality was not only useable, but quite good. Much better than I had expected from t-con stacked on a zoom. Manual focus could provide sharp results with all three cameras..