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Depth of Field Equations

http://www.dofmaster.com/equations.html

Hyperfocal distance, near distance of acceptable sharpness, and far distance of acceptable sharpness are calculated using the following equations*:

Hyperfocal distance:

H = \frac{f^2}{Nc}+f

Near distance of acceptable sharpness:

D_n = \frac{s(H-f)}{H+s-2f}

Far distance of acceptable sharpness:

D_f = \frac{s(H-f)}{H-s}

where:
H is the hyperfocal distance, mm
f is the lens focal length, mm
s is the focus distance
Dn is the near distance for acceptable sharpness
Df is the far distance for acceptable sharpness
N is the f-number
c is the circle of confusion, mm

f-number is calculated by the definition N = 2i/2 , where i = 1, 2, 3,… for f/1.4, f/2, f/2.8,…

Calculations using these equations must use consistent units. When focal length and circle of confusion have units of millimeters, the calculated hyperfocal distance will have units of millimeters. To convert to feet, divide H by 304.8. To convert to meters, divide H by 1000.

An online calculator of DoF

Another

An DoF calculation example: Canon T3i(1.6x CF), Canon 50mm F1.8 lens, Object distance 0.45m, a very shallow 0.49 cm DoF is produced by the lens.

Subject distance 45 cm
Depth of field
Near limit 44.8 cm
Far limit 45.2 cm
Total 0.49 cm
In front of subject 0.24 cm (50%)
Behind subject 0.25 cm (50%)
Hyperfocal distance 7389.6 cm
Circle of confusion 0.019 mm

==================================

*Greenleaf, Allen R., Photographic Optics, The MacMillan Company, New York, 1950, pp. 25-27

 

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Categories: Photography
  1. September 7, 2012 at 11:39 am

    Great advice. Thanks

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