Nikon 1713, 1714 instruction manual Focus Tracking, Focal length, Front-Curtain Sync, Guide number

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Focus Tracking

Enables the camera to analyze the speed of a moving subject according to the focus data detected, and to obtain correct focus by anticipating the subject's position--at the exact moment of exposure.

Lock-On™ Autofocus keeps focus firmly on a main subject during Focus Tracking even if some other object momentarily blocks it in the viewfinder.

Focal length

The distance from the principal point to the focal point. In 35mm-format cameras, lenses with a focal length of approx. 50mm are called normal or standard lenses. Lenses with a focal length less than approx. 35mm are called wideangle lenses, and lenses with a focal length more than approx. 85mm are called telephoto lenses. Lenses which allow the user to continuously vary the focal length without changing focus are called zoom lenses.

Front-Curtain Sync

The flash fires an instant after the front curtain of a focal plane shutter has completed its travel across the film plane. This is the way the N65/ N65QD operates with the flash sync mode at Normal Sync. (See "Rear-Curtain Sync" .)

Guide number

The guide number indicates the power of a flash in relation to ISO film speed. Guide numbers are quoted in either meters or feet. Guide numbers are used to calculate the f/stop for correct exposure as follows:

guide number

fI stop = --.::.......-------

flash-to-subject distance

Using a selected aperture, we can calculate the required flash-to-subject distance with the formula:

guide number

flash-to-subject distance ==---,:-:----

f/stop

Useful for determining the maximum flash-to-subject distance for flash photography.

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