GLOSSARY^209
memory card reader A computer component or an attachment that reads the image data on a
card and sends it to the computer.
Memory Stick A flash memory storage device shaped like a stick of gum, developed by Sony,
that can hold up to 8GB of data.
metering, autoflash Measurement of light that occurs when a light sensor meters the light
reflected by a subject after the flash begins firing. The flash output is then controlled instantly so that
the subject is exposed properly.
metering, center-weighed A light reading that emphasizes the intensity of light reflected from
objects in the center of the viewfinder’s frame.
metering, matrix A light meter reading produced by reading the light from several areas
throughout the frame.
metering, spot A light reading taken of a narrow area, smaller than that used in center-
weighted metering, usually in the center of the frame.
midtones Light values in an image midway between the lightest and darkest tones. See also
zone system.
MPEG A digital video format developed by the Motion Picture Expert Group.
N–O
NiCad batteries(alsonicadandNiCd) Once a serious improvement over common
alkaloid-based batteries, nickel cadmium batteries are losing favor because they must be recharged
frequently.
NiMH batteries Rechargeable nickel metal hydride batteries store up to 50% more power than
NiCad batteries.
nodal points The front nodal point in a compound lens is where rays of light entering the lens
appear to aim. The rear nodal point is where the rays of light appear to have come from after pass-
ing through the lens. The nodal point (singular) is often wrongly cited as the point around which a
camera should rotate to avoid parallax error. The correct point is the entrance pupil.
noise A random distortion in an analog signal causing dark or colored flecks in an image, partic-
ularly in dark areas. It can be caused by electronic noise in the amplifiers that magnify the signals
coming from the image sensor, nearby electrical spikes, heat, or other random electrical fluctuations.
Noise is more prevalent at higher ISO levels.
normal lens A lens with about the same angle of view of a scene as the human eye—about 45°.
optical character recognition (OCR) A scanning technology that recognizes letters and trans-
lates them into text that can be edited onscreen.