Focus Tracking
Enables the camera to analyze the speed of the moving subject according to the focus data detected, and to obtain correct focus by anticipating the subject'sposition-and driving the lens to that position-at the exact moment of exposure.
f-number
The numbers on the lens aperture ring and on the camera'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.
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 N70 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:
fI t _ guide number
s op - flash-to-subject distance
Using a selected aperture, we can calculate the required flash- to-subject distance with the formula:
flash-to-subject distance = 9Uidf~s~~;ber
Useful for determining the maximum flash-to-subject distance for flash photography.
