Euan said:You should get away with the 1.4 but id steer clear of the 2x
could you track birds or fast moving objects with it with no problems,like hunting.I use the Sigma 2x with my 70-200 2.8 and get on fine with it.
Andy
studioworks said:I used to have a kenko 1.4x with my old sigma 70-200 but I was never happy with it, sold it and bought a sigma 1.4x and found a world of difference, tracked fine in aiservo and quality was great.
piggin said:I recently purchased the Sigma 70-200mm f2.8 EX DG OS HSM for my Canon 50D.
I also purchased the Kenko pro 300 1.4x tc & Kenko pro 300 2x tc.
After placing some tape over the first 3 pins on both units, the IQ & AF are both excellent.
The 1.4 is a little quicker & locks onto an object that little bit faster.
Generally, I am very happy with both purchases.
taping the contact is for lenses with tc thaa have a apature of bigger than f5.6 so the 70-200mm with a 2x on will be fine on any canon body, now if you wanted to put a 300f4 with a 2xtc on anything opther than a 1d series it willneed taping but will slow down the af.I recently purchased the Sigma 70-200mm f2.8 EX DG OS HSM for my Canon 50D.
I also purchased the Kenko pro 300 1.4x tc & Kenko pro 300 2x tc.
After placing some tape over the first 3 pins on both units, the IQ & AF are both excellent.
The 1.4 is a little quicker & locks onto an object that little bit faster.
Generally, I am very happy with both purchases.
Why did you tape up the contacts?
Both TCs should focus as normal?