Learning Event 12

CALCULATE DEPTH OF FIELD

1. To mathematically compute the range of the depth of field, the point

which the lens is focused on and the hyperfocal distance is used for this

calculation.

2. Using a 35mm camera, permissible Circle of Confusion of .002, with a

75mm lens, aperture set at f/8, and the lens focused at 15 feet, calculate

the hyperfocal distance from the formula in para 3b.

a. The hyperfocal distance is 46.8 feet.

b. The near and far point of acceptable sharpness are determined using

the following formula.

c. The formula is expressed as:

As shown from the formula above, the range of the depth of field is

10.7 feet because the nearest point of acceptable sharpness is 11.3 feet

from the lens and the farthest point is 22 feet from the lens (22 feet minus

11.3 feet equals 10.7 feet). Always subtract the near point from the far

point.

3. Depth of field scale.

Experience will help you predict the best

aperture to get the depth of field you want. But you do not have to guess

the correct aperture all the time or use formulas.

a. Most lenses have a depth of field scale to guide you. This scale

indicates the distance range in which the subjects will be in acceptable

focus at different f/stops.