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Glossary-2 April 28, 2004
Depth of field The zone of sharpest focus in front of, behind, and around the subject.
EV (Exposure value) A numeric value that expresses the amount of light for a given exposure. It
depends on the brightness of the photographic subject and the sensitivity of
the imager. If a photographic subject is bright, the EV will be large, and if
the subject is dark, the EV will be small. If twice the amount of light reaches
the imager’s surface, the difference in exposure value will be +1, and if half
the amount of light reaches the imager’s surface, the exposure value
changes by -1.
Exposure The amount of light reaching the image's surface. The exposure is
controlled by the combination of aperture and shutter speed.
Exposure Compensation This function lets you intentionally overexpose or underexpose a picture.
Exposure modes Program Auto: Camera sets both shutter speed and aperture for correct
exposure.
Shutter Priority Auto: You select the shutter speed and the camera sets
the appropriate aperture for correct exposure.
Aperture Priority Auto: You select the aperture and the camera sets
appropriate shutter speed for correct exposure.
Manual: You select both shutter speed and aperture, according to
indications on the exposure meter
f-number The numbers on the lens aperture ring that indicate the relative size of the
lens aperture opening.
Histogram The image histogram shows the range and distribution of tonal values for an
image. The tick marks at the bottom of the histogram represent
photographic stops relative to the factory-determined 18% gray level. The
range of stops is from +3 to -7. The double bar tick mark indicates the
exposure value associated with 18% gray. Tick marks to the right of the
double mark indicate one-stop increments brighter than 18% gray, and tick
marks to the left indicate one-stop increments darker than 18% gray.
ISO ISO is the international standard for representing film sensitivity. The higher
the number, the greater the sensitivity, and vice versa. For example, ISO 200
is twice as sensitive as ISO 100, and half that of ISO 400. When you change
the ISO setting on your camera, you adjust the sensitivity of the imager
equivalent to the corresponding film sensitivity.
JPEG Joint Photographic Experts Group has established a standard method for
compressing and decompressing digitized images. If the rate of
compression is high, the file size will be small but picture quality will be
decreased.