Is the Sigma 23mm F1.4 DC DN Contemporary Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 23mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Sigma 23mm F1.4 DC DN Contemporary Lens set to 23mm f/4.0 sharper than the Sigma 24mm F1.4 DG DN Art Lens set to 24mm f/2.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.