Depth of Field Scale
Markings on a lens barrel showing the near and far limits of sharpness for each aperture at the set focus distance.
Measured in
m / ft
In depth
The scale is a pair of aperture numbers mirrored either side of the focus index; reading the distances opposite them gives the depth of field directly, and setting infinity against the far mark achieves hyperfocal focus in one movement. Modern autofocus lenses have largely dropped the scale, which is one practical reason zone focusing has fallen out of everyday use.
Examples in practice
Turning the ring until infinity sits opposite the f/16 mark puts everything from 1.2 m to the horizon within the scale's limits.