Depth of field is the range of distance that appears sharp in an image. Some photographs have everything in focus, from foreground to background. Others isolate a single subject and blur the rest. Both effects are controlled by depth of field, and understanding it is one of the most useful skills in photography.

Three factors determine depth of field. Aperture is the most direct: a wide aperture like f/2.8 produces shallow depth of field, while a narrow aperture like f/16 produces deep depth of field. Distance matters too. The closer you are to your subject, the shallower the depth of field. Focal length also plays a role. A telephoto lens compresses the scene and produces shallower depth of field than a wide lens at the same aperture. Sensor size adds another variable. A smaller sensor produces more depth of field at the same field of view and aperture. Photographers use these factors together to control what is sharp and what is not.

What affects depth of field

• Aperture. Wider apertures produce shallower depth of field.
• Distance. Closer subjects produce shallower depth of field.
• Focal length. Longer lenses produce shallower depth of field.
• Sensor size. Smaller sensors produce deeper depth of field at the same settings.

Depth of field is not just a technical setting. It is a way of directing attention. What is sharp is what matters.