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Flash synchronization, F-number, Hyperfocal distance – Nikon Camera N90 User Manual

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Flash synchronization

The timing of the flash so it fires coincident with the operation of
the camera's shutter. There are two types of synchronization:

Normal Sync which fires the flash at the start of the exposure,

and Rear Sync which fires the flash at the end of the exposure.

f-number

The numbers on the lens aperture ring and on the N90’s LCD

which indicate the relative size of the lens aperture opening.

The f-number series is a geometric progression based on

changes in the size of the lens aperture, as it is opened and
closed. As the scale rises, each number is multiplied by the

factor 1.4. The standard numbers for calibration are 1.0,1.4, 2,

2.8, 4, 5.6, 8, 11, 16, 22, 32, etc., and each change results in a
doubling or halving of the amount of light transmitted by the

lens.

Hyperfocal distance

The closest point a photographer can focus on where the

depth of field includes infinity. When the lens is focused for

hyperfocal distance, the deepest depth of field, covering from

1/2 the hyperfocal distance to infinity, can be obtained at each

f/stop. The longer the focal length, the longer the hyperfocal

distance; the smaller the aperture (the larger the f/number), the
shorter the hyperfocal distance.