Yes. As you stop the lens down to higher f-stop numbers (smaller apertures), diffraction becomes more noticeable. Diffraction is a physical effect where light spreads slightly as it passes through a very small opening, which reduces fine detail and makes the image look softer.

That’s why there is usually a trade-off:

• wider apertures: less diffraction, but shallower depth of field
• smaller apertures: more depth of field, but less absolute sharpness

In macro photography this trade-off is especially important because depth of field is extremely thin, so photographers often accept some softness from diffraction in order to get more of the subject in focus.