Re: Blech! How can you stand 640x200??

["Simon Biber" <simon@basilisk2.cjb.net>]

Television uses an interlaced display, where every second scanline is sent
out in any particular frame. The Apple II sends out the same image for two
consecutive frames, so that two adjacent scanlines actually will contain the
same data. This is why the Apple's VBI (vertical blanking interrrupt) is
only 25 Hz not 50 Hz.

The total 525 scanlines are split between the two frames, so that one gets
262 and one 263 lines, and these are interspersed. So there is really only
62 "spare" lines above and below the image on a IIgs 200 line mode.

I do agree that it looks awful. I prefer modes which use a correct aspect
ratio so that the pixels are square. The HGR 280x192 isn't too bad on most
monitors. Even 320x200 looks squat, as it should be 320x240 for square
pixels.

Simon.


"Mr. Boffo" <mister_boffo@hotmail.com> wrote in message
3a46b23b.48241961@news.wi.centuryinter.net">news:3a46b23b.48241961@news.wi.centuryinter.net...
> So anyway I've been trying out stuff like Hyperstudio for the IIgs,
> and the one thing which keeps coming to mind is: "Boy, this screen is
> just godawful!"
>
> What exactly was the point of limiting the IIgs to a maximum of
> 640x200? The pixels are so irregularly shaped that the screen images
> look horrendous. At this point my only guess is that memory cost too
> much for the extra resolution to be worthwhile.
>
> Now, the 320x200 mode is just fine and dandy. That mode is quite nice.
> But 640x200 totally blows. The text looks terrible, unless you make it
> double wide to compensate for the unnatural skinniness that 640x200
> imposes on everything.
>
>
> This reminds me of something that's always bothered me.. how is it
> that the image appears to really only have 200 lines, when NTSC is
> really 525 lines? I realize the edges are blank and unused to prevent
> overscan, but still, at 200 scanlines tall you'd have a squashed
> letterbox in the middle and 162 blank scanlines above and below.
>
> It would seem that those 200 image scanlines are double-thick, yet
> when you look at the graphics on an NTSC monitor you can't tell that a
> pixel is two scanlines tall. Even with the old hires 280x192 grahpics,
> a pixel appears to be made up of a single scanline, with a definite
> separation from the next pixel above and below but no visible split in
> the pixel itself. Is this really a "normal" NTSC resolution at all?
>
> -Mr. Boffo
>
> Email: mister_boffo@hotmail.com