Jae, I used to have the 35-70 used on a 1Ds2. While the resolution and micro contrast are as you would expect from Zeiss and even more, the 3D isn't that great. It is also very difficult to focus, even with the split image screen. I did a comparison with the ZA 24-70 before I sold my Canon and Contax gear, and at close range, the ZA smoked the Contax at all FL and apertures. At infinity, as you can guess, the Contax was better only in the corners. The resolution of the ZA is simply unbelievable on 80% of the frame. I know the resolution of the sensors is not the same, but the 16.7 mp of the canon are kinder on the lenses than the a900.