Calculating Difference in DOF at Different Focal Lengths / Same Framing

[HDNitehawk]

So, how would this not apply to macro distances?

[neuroanatomist]

So, how would this not apply to macro distances?

The equations on which the DoF calculators are based have an underlying assumption that the lens is 'thin' (a single element with no thickness). At 'normal' subject distances, the error introduced by the difference in entrance pupil position between the assumed thin lens and the real lens is insignificant, but at macro distances that error has a real impact on the DoF.

[Sean Setters]

Thanks Neuro. I appreciate the explanations.