Image quality -
PC camera has to faithfully reflect and reproduce true color of
observed object, any distortion of image or twisted of color will consider being poor
image quality. Since the responses of human eyes to color are slightly different, some
testing equipment and environment is necessary to accurately judge the image quality.
Nevertheless, image sensor, lens and design method is the key factors of image quality.
Another criteria of image quality is the sensitivity to environmental luminance, some
PC camera can sense the image in dim condition for light source as low as 5 luxs, while
others can respond in 10 luxs only.
Lens -
Lens is another critical component in PC camera that can affect the quality
of image sensed. The focal length and viewing-angle of lens, associated with IR-cut
and low-pass filter, will determine the picture quality sensed. The most popular lens
used in PC camera market is 1/3”,1/4” and 1/5” lens, with 3.6 ~ 6.0 mm focal length
each has their own advantages in different applications. To avoid distortion on edge of
image, focal length above 4.0 mm is recommended.
Performance and resolution -
The performance of PC camera is
determined by frame size (resolution) and frame-per-second PC camera can handle.
Frame size has certain standard for comparison, so-called SQCIF (160 x 120), QCIF
(176 x 144), CIF (352 x 288) and VGA (640 x 480). Analog PC camera can transmit up
to 30 frames/second at any resolution, which is almost the highest quality similar to the
motion picture as you see in the cinema.
Still 18 frames/second claims to be acceptable in digital PC camera, although some
jerking image may occur and cause inconvenience for visual effect. The new USB or
parallel port PC camera with compression technologies should be able to support up to
30 frame-per-second in CIF formats.
