Vibration Compensation / Image Stabilization
The key advantage of the Tamron 24-70mm f/2.8 over all other 24-70mm lenses on the market today is its image stabilization feature, which Tamron calls “Vibration Compensation”. Tamron claims that the VC technology provides up to 4 stops of stabilization, similar to Nikon’s claim on its VR II technology. I personally found the 4 stop claim to be an overstatement for both VC and VR II, especially on high resolution cameras like Nikon D800 and D7000. Realistically, I would say that both VC and VR II provide up to about 2.5-3 stops of advantage, with the latter being a little more consistent.
Read more: http://photographylife.com/reviews/tamron-24-70mm-f2-8/2#ixzz2yCU53hgS