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.
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