Nikon 55MM F/2B Manual de instruções - Página 21

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When non-TTL meter is used

At close ranges (reproduction ratios greater than

1:10), the amount of light reaching the film decreases

as the lens-to-film distance increases. When non-TTL

measurement is used for this range, the result is under-

exposed photographs unless compensation has been

made for this decrease. (When the Micro-Nikkor 55mm

f/2.8 lens is used with the Photomic or Nikkormat

TTL meter it is not necessary to make compensations,

since the meter is designed to give an accurate reading

of the amount of light reaching the film.)

The table on the right gives the exposure factors (com-

pensation values) with exposure increase in f/stops for

non-TTL exposure measurement at reproduction

ratios greater than 1:10.

To calculate the necessary corrections in shutter

speed rather than in aperture value, multiply a given

exposure factor by the exposure time. For instance,

if the normal exposure at a 1:1 reproduction ratio is

1 /8 second, the correct shutter speed is 1 /8 x 4 = 1/2

second.

The following formula is used to calculate the expo-

sure factor: Exposure factor = (1 + R)

where R = Reproduction ratio

Reproduction

ratio

1/10

1/8

1/6

1/4

1/2

1/1.8

1/1.6

1/1.4

1/1.2

1/1

Exposure

factor

1.2

1.3

1.4

1.6

2.3

2.4

2.6

2.9

3.4

4.0

Exposure

increase

in f/stops

a p p r o x . 1 / 3

approx. 1/3

a p p r o x . 1 / 2

a p p r o x . 2 / 3

approx. 1-1/3

a p p r o x . 1 - 1 / 3

a p p r o x . 1 - 1 / 2

approx. 1-2/3

a p p r o x . 2