What effect does a smaller aperture have on depth of field?

A smaller aperture, indicated by a higher f-stop number, increases the depth of field in a photograph. When the aperture is smaller, more of the scene from the foreground to the background is in focus. This is particularly useful in landscape photography or situations where you want to maintain detail across the entire image.

The physics behind this can be understood through the principles of optics: as the aperture decreases in size, the lens allows a narrower beam of light to enter, which enhances the zone of acceptable sharpness around the point of focus. Consequently, this means that objects at varying distances from the camera lens maintain greater sharpness relative to one another, resulting in an increased depth of field.

In contrast, a larger aperture decreases depth of field, leading to a more pronounced background blur, which is often desired in portrait photography. Therefore, the choice that a smaller aperture increases depth of field aligns with fundamental photographic techniques and principles.