tokina 12-24 not sharp ?

Dear all,

I tried to compare tokina 12-24 at 24mm with great 28-70/2.8 at 28mm.
Both at f4. The difference is huge: 28-70 seems to be much sharper.

Is it normal or did I get soft tokina ? (compared with prime nikon 20/2.8 is my tokina quite good, as mentioned in other thread).

Here is 100% crop Tokina at 24/4, focus on infinity

Here is 100% crop Nikon 28-70 at 28/4, focus on infinity

thanks

andre