Aperture and diffraction explained
How to deal with fuzziness you get from using smaller apertures
Digital Lens Optimizer slows down the performance of DSLRs, but EOS R System cameras don’t suffer from this problem
Despite increasing the depth of field, the smallest aperture on a lens can actually decrease the overall sharpness of your pictures. This is due to the effects of diffraction – where light effectively bends around the edges of the aperture blades that open and close to form the opening in the lens, and spreads out. Diffraction happens at all aperture settings, but it becomes more pronounced as the aperture decreases in size.