Understanding Depth of Field
Depth of field (DoF) is the distance range in which objects appear acceptably sharp. It depends on focal length, aperture, subject distance, and sensor size.
Key Concepts
Hyperfocal Distance: The closest focus distance at which everything from half that distance to infinity is acceptably sharp.
Circle of Confusion (CoC): The largest blur circle that still appears as a point to the human eye, dependent on sensor size and viewing conditions.
How to get shallow DoF: Use a wider aperture (smaller f-number), longer focal length, or move closer to your subject.