Depth Of Field
Depth of field is the range of distances in front of and behind the exact focus point that still reads as acceptably sharp. It narrows with a wider aperture (a lower f-number), a longer real focal length at a fixed distance, or a closer subject distance — and widens with the opposite of each: a narrower aperture, a shorter focal length, or a more distant subject.
The boundary between 'sharp' and 'not sharp' isn't a hard physical line — it's set by circle of confusion, a chosen acceptable-blur threshold, which is why depth of field also depends on sensor size: a smaller sensor's stricter threshold narrows depth of field at a fixed real focal length, even though matching a full-frame shot on that smaller sensor (which needs a shorter real lens) typically ends up more forgiving overall.
Frequently Asked Questions
What's the difference between depth of field and hyperfocal distance?
Depth of field is the general concept — the sharp range at any given focus point. Hyperfocal distance is a specific focus point: the closest distance you can focus at while still keeping infinity within that sharp range.
Does depth of field depend on my camera's resolution?
No — it depends on sensor physical size, focal length, aperture and subject distance, not megapixel count. Two cameras with the same sensor size but different resolutions compute identical depth of field at the same settings.