How does a larger aperture affect depth of field?

A larger aperture, which is represented by a smaller f-stop number, decreases the depth of field in an image. This means that when the aperture is wide open, the area of sharp focus is limited to a smaller zone in front of and behind the subject being photographed. This characteristic of a larger aperture is particularly useful in portrait photography, where you may want to isolate the subject against a softly blurred background, thus drawing more attention to the subject itself.

In contrast, a smaller aperture (larger f-stop number) increases the depth of field, resulting in more of the scene being in focus. Understanding the relationship between aperture and depth of field is essential for controlling the visual impact of a photograph. Additionally, the notion that it could create a vignette effect, or have no effect at all, does not align with the fundamental principles of photography regarding aperture and depth of field.