DxOMark tested the Sony FE 16-35mm f/2.8 G Master lens mounted on the Sony α7R II and the lens buried the competition. The 16-35mm f/2.8 GM received an overall score of 42 on the DxOMark scale, putting it six points ahead of its nearest competitor, and a record score of 34 for sharpness, which was 10 points ahead of any other lenses!
"Another big strength of the Sony is that its image quality remains very consistent across its entire focal range — a relief for those accustomed to having to remember to coddle their lenses if they are weak at some parts of their range. Sony’s sharpness, for example, is ahead of its competitors over its entire zoom range."
"With the new Sony EF 16-35mm f/2.8 lens, you are simply getting better quality images for about the same price you would pay for many of its f/2.8 wide-angle zoom competitors. Obviously this comes with the caveat that it helps you only if you are shooting with E-mount Sony cameras, especially their latest high-end models." - David Cardinal, DxoMark
You can see the full review at DxOMark.com