Editing Depth of field (section)

==DOF scales==
Many lenses include scales that indicate the {{abbr|DOF|depth of field}} for a given focus distance and {{nowrap|f-number}}; the 35&nbsp;mm lens in the image is typical. That lens includes distance scales in feet and meters; when a marked distance is set opposite the large white index mark, the focus is set to that distance. The {{abbr|DOF|depth of field}} scale below the distance scales includes markings on either side of the index that correspond to {{nowrap|f-numbers}}. When the lens is set to a given {{nowrap|f-number}}, the {{abbr|DOF|depth of field}} extends between the distances that align with the {{nowrap|f-number}} markings.

Photographers can use the lens scales to work backwards from the desired depth of field to find the necessary focus distance and aperture.{{sfn|Ray|1994|p=315}} For the 35&nbsp;mm lens shown, if it were desired for the {{abbr|DOF|depth of field}} to extend from 1&nbsp;m to 2&nbsp;m, focus would be set so that index mark was centered between the marks for those distances, and the aperture would be set to {{f/|11}}.{{Efn|The focus distance to have the {{abbr|DOF|depth of field}} extend between given near and far object distances is the harmonic mean of the ''object conjugates''. Most helicoid-focused lenses are marked with image plane-to-subject distances,{{citation needed|date=September 2019}} so the focus determined from the lens distance scale is not exactly the harmonic mean of the marked near and far distances.}}

On a view camera, the focus and {{nowrap|f-number}} can be obtained by measuring the depth of field and performing simple calculations. Some view cameras include {{abbr|DOF|depth of field}} calculators that indicate focus and {{nowrap|f-number}} without the need for any calculations by the photographer.{{sfn|Tillmanns|1997|p=67-68}}{{sfn|Ray|1994|p=230-231}}

<gallery widths="200px" heights="200px">
File:DOF scale detail.png|Detail from a lens set to {{f/|11}}. The point half-way between the 1&nbsp;m and 2&nbsp;m marks, the {{abbr|DOF|depth of field}} limits at {{f/|11}}, represents the focus distance of approximately 1.33&nbsp;m (the reciprocal of the mean of the reciprocals of 1 and 2 being 4/3).
File:TessinaDOF.jpg|{{abbr|DOF|depth of field}} scale on Tessina focusing dial
</gallery>