|
The
TV Camera > Operating Characteristics > Signal
to Noise
|
ABOVE:
A picture with a LOW signal-to-noise
ratio. The proper term for the "snow"
is "noise."
BELOW: A pictue with a HIGH signal-to-noise
ratio--for comparison purposes.
|
|
|
SIGNAL
TO NOISE RATIO
"Signal-to-noise" describes a ratio
between the television signal and background static.
You
already know that a distant TV station—pulled in
with a rabbit ears antenna—will have a lot of "snow"
in the image. The correct term for that snow is "noise."
That distant station has a low signal-to-noise
ratio by the time it reaches you.
Conversely,
a station nearby might have a crystal-clear image: that
is, a high signal-to-noise ratio. With a high
signal to noise ratio, the picture is so good, you don't
see ANY noise.
The
concept works equally well for audio. If you play back
an audio cassette recording of a quiet passage of music,
you will hear the noise or "hiss" in the background
because of the low signal-to-noise ratio. But if you
play back music on a CD—which inherently has a
high signal-to-noise ratio, the hiss is gone.
In
either case, signal to noise is measured in Db (Decibels).
55db might be the signal-to-noise ratio of a good video
camera. 30db would be unacceptably poor.
|