Focus & Depth of Field — 60 Terms Defined

Focus Limiter Focus & Depth of Field m A switch that restricts a lens's focusing range, so autofocus does not search through distances the subject cannot occupy.

Focus Lock Focus & Depth of Field Holding the current focus distance so that further movement of the camera or subject does not trigger refocusing.

Focus Magnification Focus & Depth of Field × magnification A function that enlarges part of the live image so focus can be judged at a pixel level.

Focus Peaking Focus & Depth of Field A display aid that outlines the highest-contrast edges in the live image, marking what is currently in focus.

Focus Priority Focus & Depth of Field A setting that prevents the shutter from firing until the camera confirms focus has been achieved.

Focus Shift Focus & Depth of Field mm A movement of the plane of sharpest focus as a lens is stopped down, caused by residual spherical aberration.

Focus Stacking Focus & Depth of Field count Combining several frames focused at different distances into one image with depth of field no single exposure could achieve.

Focus Throw Focus & Depth of Field degrees The angle through which a focus ring must turn to travel from minimum distance to infinity.

Focus-by-wire Focus & Depth of Field A manual focus ring that sends an electronic signal to a motor rather than moving the optics mechanically.

Front Focus Focus & Depth of Field mm A calibration error in which a lens consistently focuses slightly nearer than the intended subject.

Hybrid Autofocus Focus & Depth of Field A system combining phase detection for speed and direction with contrast detection for final precision.

Hyperfocal Distance Focus & Depth of Field m The focus distance that yields the greatest depth of field, extending from half that distance out to infinity. H = f² / (N × c) + f

Infinity Focus Focus & Depth of Field m The lens setting at which parallel rays from very distant objects converge on the sensor.

Low-light AF Rating Focus & Depth of Field EV The dimmest light level at which a camera's autofocus is specified to work, quoted in EV at a stated aperture and ISO.

Magnification Ratio Focus & Depth of Field ratio The ratio between the size of a subject and the size of its image on the sensor. m = image size / subject size

Manual Focus Focus & Depth of Field m Focusing by turning the lens ring by hand while judging sharpness visually or by scale.

Microprism Collar Focus & Depth of Field A ring of tiny prisms around a focusing screen's centre that shimmers when the image is out of focus and clears when it is sharp.

Minimum Focus Distance Focus & Depth of Field m The closest a subject can be to the sensor plane and still be brought into focus.

Parfocal Lens Focus & Depth of Field A zoom lens that holds focus on the same subject as the focal length is changed.

Phase-detection Autofocus Focus & Depth of Field A focusing method that splits incoming light into two views and measures their separation to determine both the amount and direction of defocus.

Plane of Focus Focus & Depth of Field m The flat surface, parallel to the sensor, at which the subject is rendered with maximum sharpness.

Prefocusing Focus & Depth of Field m Focusing in advance on the spot where the subject will be, then firing as it arrives.

Release Priority Focus & Depth of Field A setting that fires the shutter whenever the button is pressed, regardless of whether focus has been confirmed.

Scheimpflug Principle Focus & Depth of Field degrees The rule that when a lens is tilted, the subject plane, lens plane and image plane all intersect along a single common line. Subject, lens and image planes share one line