Is the Irix 15mm f/2.4 Blackstone Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 15mm f/2.4 test image. Observe the contrast and resolution of these results.
Is the Irix 15mm f/2.4 Blackstone Lens set to 15mm f/2.4 sharper than the Canon EF 11-24mm f/4L USM Lens set to 18mm f/16.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.