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From: brian@sdcsvax.UUCP (Brian Kantor)
Newsgroups: net.micro,net.micro.amiga
Subject: Re: Amiga monitor
Message-ID: <1083@sdcsvax.UUCP>
Date: Wed, 4-Sep-85 13:03:30 EDT
Article-I.D.: sdcsvax.1083
Posted: Wed Sep  4 13:03:30 1985
Date-Received: Sun, 8-Sep-85 16:19:09 EDT
References: <1204@tekgvs.UUCP> <577@sftig.UUCP>
Reply-To: brian@sdcsvax.UUCP (Brian Kantor)
Organization: UCSD wombat breeding society
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Xref: watmath net.micro:11861 net.micro.amiga:74

In article <577@sftig.UUCP> rbt@sftig.UUCP (R.Thomas) writes:
>OK.  I give up.  Will somebody please explain what the difference between the
>various color input types are.   What is the difference between RGBI digital,
>RGB analog, and NTSC composite, and all the rest.  
>Rick Thomas ihnp4!attunix!rbt

Quickly:
	Analog inputs allow you to have continuous shades displayed of
	the input signal - for monochrome, you get shades of grey; for
	RGB analog you can vary the three input Red Green and Blue
	inputs and get just about every color possible.  (Analog signals
	generally vary from 0 = black to 1 = full on volts).

	Digital inputs allow no shading - either the signal is full on
	or its off, and so with the color or brightness.  Digital RGB
	therefore allows you the primary colors, mixtures of any two of
	them, and black and white.

	RGBI adds an intensity input to (typically) cut brightness in
	half for all colors.  This gives you pastel shades of the
	primary and secondary colors, and adds a single shade of grey.

	NTSC (National Television Standards Council) (also known as
	Never Twice the Same Color) is a method of encoding analog color
	and brightness signals using a complex combination of amplitude
	and phase relationships into a single signal.  It is inherently 
	limited in resolution when compared with RGB analog, and so is 
	not used for medium or high resolution displays.  It also tends
	to be less stable, as the phase relationships are delicate.

	Composite signals usually refer to the inclusion of synchronizing 
	signals combined with the video.  Sync can also be sent separately.  
	Composite sync with vertical, horizontal, and color is customary 
	with NTSC, a separate sync source is common with RGB.  

	A small confusion exists here, in that a separate sync feed that 
	contains both vertical and horizontal sync, rather than two 
	separate sync feeds, can also be called composite sync.  
	To top it all off, it is real common to feed composite sync on top 
	of the green signal to an RGB monitor in order to reduce the number 
	of pieces of coaxial cable running around underfoot.

Hope this helps some.

	Brian Kantor	UC San Diego Computer Graphics Lab

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