Date   : Sun, 04 Apr 2004 20:42:09 +0100 (BST)
From   : Pete Turnbull <pete@...>
Subject: Re: Aspect ratio question

On Apr 4, 12:15, Jonathan Graham Harston wrote:

> Hold on, hold on!  Aren't you all going about this the wrong way
round?
> You're assuming you have perfect display equipment and perfect
optical
> receptors. Even for translating a display via emulation your are
still
> assuming that the host hardware is displaying on a perfect display.
>
> What we always used to do was (and what I still do):
>
> Draw a square:
> MODE 0
> MOVE 128,0:DRAW 1279-128,0:DRAW 1279-128,1023:DRAW 128,1023:DRAW
128,0
>
> Carefully measure the displayed square. On my monitor here that's
168mm
> each side.
>
> And then carefully adjust the *MONITOR* to ensure the square was
displayed
> square.
>
> If a square that has the same number of pixels on each side does not
look
> square, then there's a problem with the *MONITOR*.

Well, only if the pixels are square (have a 1:1 aspect ratio), which is
what we were arguing about.  I'm on your side, as far as a Beeb or a
1024x768 or 1280x1024 display is concerned, but not all pixels are
square: the standard for digital video uses non-square pixels, for
example.

Actually, after doing a lot of arithmetic over the course of this, er,
discourse, I'm inclining to the idea that Beeb pixels aren't quite
square, but not as far as Thomas' estimate goes.

We've been assuming that the monitor or TV connected to a Beeb should
be set up according to the PAL standard.  Perhaps it should be
"tweaked" ;-)


-- 
Pete						Peter Turnbull
						Network Manager
						University of York