Demystifying diffraction

It’s important to note that any light travelling through your lens does so in wave form. When it passes through the aperture, it spreads out before hitting the sensor. This spreading effect is called diffraction. With wide apertures it’s minimal, but with smaller ones it gradually becomes more severe. At the very smallest apertures it can be so severe that it creates a fuzzy image on the sensor. We recommend sticking to f/11 or f/16 or below on Aps-c/full-frame Nikons.

A small aperture means significant bending of light and a fuzzier image.

When using a wide aperture you get minimal bending of light waves.