dandig wrote in post #11302118
I have done a
full review here on my site
with a comparison to the 70-200 f4 L IS.
The people that keep saying "oh it doesnt have f2.8" or "you can get a 70-200 f2.8 for a bit more" have really missed the point of this one I think. This lens is not a competitor to the f2.8 lenses. If you need f2.8 then you are saying you need a wide aperture. So you should never consider a f4-f5.6 lens for you. It just won't cut it. BUT many people seem to think they need an f2.8 lens just because that is seen a "pro feature". I used to have a 70-200 f2.8 and I sold it because I never shot it at f2.8 anyway. Guess what, I'm a professional photographer! Who would have thought it

If you have no need for a faster shutter speed in low light, or the subject isolating ability of f2.8 then do take a look at this 70-300. Its a fantastic lens.
The 1.4 TC III is going to be about $500 so your solution will end up being $600 more. Thats a significant increase which really puts it outside the realms of direct comparison.
But the 1.4x III TC can be used with all sorts of other lenses too. And if the 70-200 f/4 IS already beats it with the 1.4x II then ith the 1.4x III....
And maybe the f/2.8 is another thing entirely, and it is, but it does go to show the over-pricing on the 70-300L.
All the same your tests show amazing promise 70-200!!, not much fear of selling the 70-200 than a bit of weight and 2/3 at 200mm. Although I wonder how close the bill was. The 70-200 f/4 IS tends to not really, really come to life until you start getting 15'plus away.
Depending how it all sorts out, if the price comes down I could perhaps sell off my 70-200 f/4 IS. I just hope it does better at 280mm than your tests suggests (and as well 70-200 when shooting far off subjects). I may get the MkIII TC for my super-tele anyway. Granted it is a real pain on the 70-200, on-off-on-off-on-off yuck!