Is the Tamron 50-300mm F/4.5-6.3 Di III VC VXD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 50mm f/4.5 test image. Observe the contrast and resolution of these results.
Is the Tamron 50-300mm F/4.5-6.3 Di III VC VXD Lens set to 50mm f/4.5 sharper than the Tamron 50-400mm f/4.5-6.3 Di III VC VXD Lens set to 50mm f/4.5? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.