Axis 262+ Manual do Utilizador descarregar pdf (Página 35)

Megapixel, HDTV / TECHNICAL CORNER 35

MEGAPIXEL

The higher the resolution, the more details can be seen

in an image. This facilitates the identication of objects

and persons – important considerations in video

surveillance. Megapixel resolution allows the same

scene to be viewed in greater detail, or a larger scene

to be viewed at a maintained resolution. The higher

resolution also means that digital pan/tilt/zoom can be

used without causing a drop in resolution.

After the video signal from an NTSC or PAL analog

camera has been digitized, the maximum resolution

will be 0.4 megapixel. New network camera technology

makes higher resolutions possible.

One common megapixel format is 1280x1024, which

gives 1.3-megapixel resolution, 3 times higher than

analog cameras. Cameras that provide multi-megapixel

resolutions are also available. It is, however, important

to bear in mind that higher resolutions generally lead

to reduced light sensitivity because of the smaller

pixels in the image sensor as compared with

conventional cameras.

The full 1600x1200 resolution provided by AXIS 223M Network

Camera gives more than 4 times the number of pixels compared with

a high-resolution analog camera.

HIGH-DEFINITION TELEVISION (HDTV)

Axis HDTV network cameras comply with SMPTE

(Society of Motion Picture and Television Engineers)

standards, guaranteeing adherence to HDTV resolu-

tions and frame rates, better color delity and a 16:9

format. The two most important HDTV standards are

SMPTE 296M and SMPTE 274M.

SMPTE 296M (HDTV 720p) denes a resolution of

1280x720 pixels with high color delity in a 16:9 for-

mat using progressive scanning at 25/30 Hertz (Hz),

which corresponds to 25 or 30 frames per second de-

pending on the country, or at 50/60 Hz (50/60 frames

per second).

SMPTE 274M (HDTV 1080) denes a resolution of

1920x1080 pixels with high color delity in a 16:9

format using either interlaced or progressive scanning

at 25/30 Hz or 50/60 Hz.

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Axis 262+ Manual do Utilizador Página 35