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Re: Legal RGB
Dean Humphus wrote:
> The third tool is a Tek 601 (or WFM 300) component scope with a
> provision to light a "GO-NO GO" tally when RGB limits are being exceeded.
> It does not tell you what particular component is out of limits though. The
> last is a device made by HP, (the name escapes me. "Color Crusher" or
> something) that sits in the monitor path for instance and annoyingly
> highlights the illegal pixals in the dispaly. It also conforms the signal
> if chosen by the user.
The newer Tek 601 scopes also incorporate their 'Arrowhead' display.
This is kind of like the bow-tie display seen on some waveform monitors,
but it represents color-space limits in composite rather than component
form. The front panel alarm will light up when the incoming video would
exceed, say , 120 units of chroma once it is encoded. The 601 scopes
only warn of illegal levels, they do nothing to correct the signal.
A few companies in addition to H-P have video limiter boxes that will
keep luminance and/or chroma levels within specified limits. They all
work fairly well with images that have few high frequency components,
like color bars. Differences start to show up in images with lots of
detail. Thanks to Mr. Nyquist, you can't just simply clip digital
component video to some arbitrary level and expect to see a
corresponding change once it gets encoded to composite analog video.
Hans Lehmann | hlehmann at encorevideo.com
Encore Video, Hollywood | hlehmann at pacbell.net