Is the Sigma 12-24mm f/4 DG HSM Art Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 12mm f/4.5 test image. Observe the contrast and resolution of these results.
Is the Sigma 12-24mm f/4 DG HSM Art Lens set to 12mm f/4.5 sharper than the Venus Optics Laowa 12mm f/2.8 Zero-D Lens set to 12mm f/11.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.