Subject: Re: Recording to VHS
From: [email-masked] (Gord Davison)
To: Multiple recipients of list <[email-masked]>
Date: Thu, 25 Apr 1996 23:48:52 -0700

>I read in one of the trade mags -- I think it was either DV or PC Graphics
>and Video -- that _VHS_ resolution is only about 320x240. Is this true? 
[SNIP]

>Al Mejias

NTSC [Never The Same Colour ;?] is actually 256 lines interlaced. That is,
the odd lines are drawn from top to bottom, and then the even -- in the same
fashion -- to complete one "frame" of video. So, this "frame" of video is 
considered to have two "fields": an odd pass and an even pass. The reason that 
horizontal lines -- especially thin ones -- are so flickery on NTSC video is 
that each field is updated _only_ every 1/30th of a second. 

In terms of horizontal resolution, common NTSC output is usually in the range
of 704 to 752 [severe overscan] pixels, but the _actual_ resolution is not 
nearly that high. I would guess that the "actual" horizontal resolution of 
NTSC would be approximately half [i.e. 376 pixels]. OTOH, pixels are really
a misnomer for describing NTSC resolution; often, NTSC resolution is described 
in terms of ns [nano-seconds] instead i.e. 35ns, 70ns. 

So, I guess in answer to your question, the closest resolution that accurately
describes NTSC resolution is 376 x 256, or 376 x 512, if you prefer. Also note 
that the NTSC palette is *NOT* 24 bit. Any colours that have an RGB colour 
component value greater than 200 are generally considered to be illegal NTSC 
colours. Thus, the spectrum of colour supported by NTSC is in the 8 million 
range [as opposed to 16.8 million for RGB].

==========================================================================
 Gord Davison                      | 2D/3D Animator � Multimedia Designer
 Phoenix Interactive Design, Inc.  |
 graphics � animation � multimedia |   "Complex problems have simple,
 [email-masked]             | easy-to-understand, wrong answers."
==========================================================================