Is the Tokina 16-28mm f/2.8 AT-X Pro FX Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 16mm f/11.0 test image. Observe the contrast and resolution of these results.
Is the Tokina 16-28mm f/2.8 AT-X Pro FX Lens set to 16mm f/11.0 sharper than the Tokina 17-35mm f/4 AT-X Pro FX Lens set to 28mm f/4.5? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.