Editing Circle of confusion (section)

===Adjusting the circle of confusion diameter for a lens's DoF scale===
The f-number determined from a lens DoF scale can be adjusted to reflect a CoC different from the one on which the DoF scale is based. It is shown in the [[Depth of field#Close-up 2|Depth of field]] article that

<math display=block>\mathrm {DoF} = \frac
{2 N c \left ( m + 1 \right )}
{m^2 - \left ( \frac {N c} {f} \right )^2} \,,
</math>

where {{mvar|N}} is the lens f-number, {{mvar|c}} is the CoC, {{mvar|m}} is the magnification, and {{mvar|f}} is the lens focal length. Because the f-number and CoC occur only as the product {{mvar|Nc}}, an increase in one is equivalent to a corresponding decrease in the other. For example, if it is known that a lens DoF scale is based on a CoC of 0.035&nbsp;mm, and the actual conditions require a CoC of 0.025&nbsp;mm, the CoC must be decreased by a factor of {{nowrap|1=0.035 / 0.025 = 1.4}}; this can be accomplished by increasing the f-number determined from the DoF scale by the same factor, or about 1 stop, so the lens can simply be closed down 1 stop from the value indicated on the scale.

The same approach can usually be used with a DoF calculator on a view camera.