AF speed: tamron 17-50 or sigma 17-70?
I recently bought the Tamron 17-50 f/2.8. While the image quality is very good on my A77, I'm not very happy with the AF: it is noisier than I thought, and quite slow.
The AF of the 35mm f/1.8 seems even faster than AF of the Tamron 17-50.
I've hesitated a lot between the Tamron 17-50 and the Sigma 17-70 HSM, and I wonder if I should send the Tamron back and buy the Sigma 17-70 instead.
The AF speed may be more important to me that the constant aperture.
Do you know if the AF on the Sigma 17-70 is significantly faster than on the Tamron 17-50?