Circle of Confusion
The Circle of Confusion as described in the 'Notes on Depth of Field' is calculated as follows:

**EF = D/d**

**RF = EF x r**

**CoC = 1/RF**

**CoC = 1 /(r x (D/d))**

where...

**EF** is the enlargment factor

**RF** is the is the resolution factor

**D** is the diagonal size of the enlarged image in mm

**d** is the diagonal size of the negative in mm

**r** is the resolution desired in the enlargement in lines/mm

**CoC** is the maximum allowable diameter of the circle of confusion on the negative (in mm) which will retain your desired print resolution, at your desired enlargement factor.

Hyperfocal Distance

The 'Hyperfocal Distance' as described in the 'Notes on Depth of Field' is calculated as follows:

**HF = (L x L) / (f x CoC)**

where...

**HF** is the 'Hyperfocal Distance' (mm)

**L** is the focal length of the lens (mm)

**f** is the aperture of the lens (f-stop)

**CoC** is the diameter of the desired Circle of Confusion (mm)

Depth of Field

The Near Focus Limit, Far Focus Limit, and Depth of Field as described in the 'Notes on Depth of Field' are calculated as follows:

**NF = (HF x D) / (HF + (D - L))**

FF = (HF x D) / (HF - (D - L))

DoF = FF - NF

where...

**NF** is the 'Near Focus Limit' (mm)

**FF** is the 'Far Focus Limit' (mm)

**HF** is the 'Hyperfocal Distance' (mm)

**D** is the focussed distance of the lens (mm)

**L** is the lens focal length (mm)