Re: Vintage Computing Advice

["Michael J. Mahon" <mjmahon@aol.com>]

Jason wrote:
> On 2009-05-01 19:16:32 +0700, gozarcollins@SPAMTRAPhotmail.com said:
>
> > Jason <jasonb1963@yahoo.com> wrote:
> >
> > > Video:  I'd like to use an existing LCD panel display I have (with VGA
> > > input).  I note that several companies manufacture composite video to
> > > VGA converter boxes for $40-$60.  Can anyone comment whether this
> > > produces an acceptable display?  I'd prefer to avoid dealing with an
> > > older CRT if I can avoid it.
> >
> >
> > I use a 15" LCD TV for my 800XL and it's ok. The colors seem a little
> > subdued. It has composite/s-video/VGA inputs.
> >
> > Here's a picture of it (if you want I can take a more up close
> > picture, in fact, I could plug my IIc+ into it and take a picture)):
> > http://gtia.com/wp/2005/12/29/old-school-meets-new-school/
>
>
> It would be interesting to see how it works on on the //c+.
>
> For the Atari, I hear the best thing to do is to pick up a set of custom 
> s-video cables (the 5-pin DIN connector has s-video output on it) and 
> use that to drive an s-video input or an s-video to VGA converter box.  
> Others have claimed this works really well.  From the pictures I've 
> seen, I'd have to agree.

S-video represents color information as QAM on a 3.58MHz subcarrier,
so all chroma is fundamentally limited to 3MHz, and practically to
bandwidth in the 1MHz-2MHz range.

The effect is that fine detail can only change color slowly,
so fine vertical lines that have the same luminance (brightness)
levels as their surround, differing only in chroma, will have
their contrast and chroma noticeably diminished.

An excellent example of this fundamental limitation of S-Video is
visible in a DVD of Star Wars connected to a monitor via S-Video.
As the opening text scrolls "back" to infinity, the width of the
font verticals diminishes considerably, and you can easily see that
then characters, gold when wide, fade until all golden color is
gone as they shrink.

This effect does not occur when chroma information is provided
with wider bandwidth, such as with Component or RGB connection.

-michael

NadaNet and AppleCrate II: parallel computing for Apple II computers!
Home page: http://home.comcast.net/~mjmahon

"The wastebasket is our most important design
tool--and it's seriously underused."