Learning Event 10

CALCULATE HYPERFOCAL DISTANCE

1. The hyperfocal distance varies with focal length, f/stop, and the

permissible size of the circle of confusion. The following formula is used

for computing hyperfocal distance. NOTE: Numerical values for the formula

must all be expressed in inches or millimeters.

For this lesson, the

formula will be expressed in inches.

a. For non-scientific

purposes,

25mm

equals

1

inch,

50mm

equals

2

inches, etc.

(1) HFD - Hyperfocal Distance

(2) FL2 - Focal Length, Squared

NOTE: To square a number you multiply it by itself.

(3) F - f/stop

(4) CoC - Circle of Confusion

(5) 12 - Convert to feet

b. The formula is written as:

c. Using a 35mm camera (which has a permissible Circle of Confusion of

.002) with a 50mm lens focused at Infinity, and an aperture of f/8, the

formula is expressed as:

(1) The 50mm focal length lens is converted to 2 inches.

(2) The aperture is f/8.

(3) The Circle of Confusion for a 35mm format is .002 inches.

(4) The 12 in the formula converts inches into feet.

(5) The hyperfocal distance works out to be 20.8 feet. When the lens

is refocused at 20.8 feet, the depth of field will extend from 10.4 feet to

infinity.

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