IS doesn't freeze movement in your subject, only removes it from the photographer.
If you use some kind of support when shooting, go for the non-IS one.
I bought the F4 IS and had the same dilemma for a while, thinking maybe I went the wrong way and should have got the 2.8 non-IS.
In the end I decided that, if I switched, I'd only end up hankering after the IS instead of the extra stop. I decided instead to wait until I could do what I really wanted and get the 2.8 IS![]()


Mmmm, I see you have the 300f4Lis, that will take a 1.4 t-con so why not use that for wildlife? keep the 70-200f4 and buy a t-con for the 300.
Would have to agree, save your money and buy the TC. I've taken some great shots with that combo, ok you need the light to achieve the best performance and autofocus speed does get hit, but for a £200-300 investment, its 2 lenses in 1. 300mm f4 or 420mm f5.6 (with 1.4x TC).
The 70-200mm F4 IS is a great lens and I think the V4 IS system would probably come close to the performance of the 70-200mm f2.8 handheld.
Hmm, how much do you use the 300mm?
How about selling the 300mm & 70-200 and using the money to fund a 70-200 F2.8 IS? You've then got the 70-200 you really want and could use it with the 1.4x to give 280mm F4, which is close to the 300mm you'd have sold, although admittedly the quality won't be quite as good.
Another possible option - sell the 70-200 f/4 IS but buy a 200mm f/2.8 IS prime?
You have sort of answered you question. The 300mm f4 + TC is on par with the 400mm f5.6. The 70-200mm f4 IS is a great lens optically.
SO.......How about keep the 70-200mm f4 IS and the 300mm f4 and save up for the 300mm f2.8 + 2x TC or 500mm f4instead

Everything sorted apart from the funding![]()

What a coincidence thats the same minor detail holding me back from getting one
To be honest Sarah I would stick with what you have for now, I never wish that I had a 70-200 when I am out photographing the birds, too short on the long end.
The leaves will be all gone soon anyway, which will help with regard the light.
Why not narrow down your choices, then hire them out for a test in the field, and see which one works best for you ?
Think of it as an investment towards picking the right lens.