Minolta X-700 User Manual download pdf (Page 31)

When you take a picture, light from the subject

passes through the lens and open shutter, striking

the film to form an image. To obtain correct

exposure for the subject's brightness and film being

used, the aperture (size of the diaphragm opening)

and shutter speed (length of time the shutter

curtain is kept open) must be controlled.

As indicated by the aperture diagram next to

each f-number in the figure, large f-numbers (e.g.,

f/16 and f/8) represent small apertures, and small

f-numbers (e.g., f/2 and f/1.4) represent large

apertures. Each standard f-number setting (e.g.,

f/8) lets in twice as much light as the next

numerically larger one (f/11) and half as much as

the next smaller one (f/5.6). This difference in

exposure between standard f-numbers is called one

"stop".

Shutter speeds are expressed in fractions of a

second (generally the reciprocals of numbers

shown on shutter-speed scales) and in seconds.

Each standard shutter speed (e.g., 1/60 sec.) allows

light to strike the film twice as long as the next

faster one (1/125) and half as long as the next

slower one (1/30). This difference between stand-

ard shutter speeds is also called one "stop".

Total exposure on the film is determined by the

combination of aperture and speed. Using the next

smaller f-number (i.e., giving one stop more expo-

sure) will balance using the next faster shutter

speed (i.e., giving one stop less exposure), and so

on. A great range of combinations (e.g., f/5.6 at

1 /30, f/4 at 1 /60, f/2.8 at 1 /125, etc., all of which

fall on the same diagonal line) will thus yield the

same total exposure.

The diagonal lines correspond to exposure values

(EV); all of the aperture/shutter-speed combina-

tions indicated by a given line will produce the

same exposure. At any specific film speed, the EV

increases by one each time the subject brightness

doubles, and thus the required exposure will

decrease by one stop. On the other hand, when the

EV is one unit lower (i.e., when the subject is only

half as bright), the exposure must be increased one

stop.

The film-speed-coupled metering system of the

camera measures the brightness of the subject and

computes the EV needed for proper exposure,

which is then used for setting the combination of

aperture and shutter speed.

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Minolta X-700 User Manual Page 31

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