Discussion:
The Aspect Ratio Mess
(too old to reply)
Quadibloc
2021-07-09 22:42:24 UTC
Permalink
Many TV sets and Blu-Ray players have built-in upscaling features. A similar technology was brought to video cards for gaming by Nvidia with their DLSS; this is on its 2.0 iteration, and in the meantime a simpler technolgy aimed at the same end is now available from AMD with Fidelity FX.
They both have 'Quality' and 'Performance' modes which upscale by 1.5x and 2x respectively.
They also both have a Balanced mode, but Nvidia upscales by 1.72x and AMD upscales by 1.7x.
This piqued my curiosity.

And when I switch resolutions on my monitor, the computer offers me a long list of resolutions. What are these resolutions, what different aspect ratios are associated with them?

Well, my idle curiosity led me to look up some facts which I now present to everyone on the page

http://www.quadibloc.com/other/asp01.htm

from which you can see just what a mess the field of possible resolutions for computer monitors is. You can learn new facts, such as the fact that "21:9" aspect ratio wide monitors really have an aspect ratio of 21.5 to 9, or 43:18. You can find collected information on the mystery of the Balanced mode.

John Savard
Johann Klammer
2021-07-10 18:00:45 UTC
Permalink
Post by Quadibloc
Many TV sets and Blu-Ray players have built-in upscaling features. A similar technology was brought to video cards for gaming by Nvidia with their DLSS; this is on its 2.0 iteration, and in the meantime a simpler technolgy aimed at the same end is now available from AMD with Fidelity FX.
They both have 'Quality' and 'Performance' modes which upscale by 1.5x and 2x respectively.
They also both have a Balanced mode, but Nvidia upscales by 1.72x and AMD upscales by 1.7x.
This piqued my curiosity.
And when I switch resolutions on my monitor, the computer offers me a long list of resolutions. What are these resolutions, what different aspect ratios are associated with them?
Well, my idle curiosity led me to look up some facts which I now present to everyone on the page
http://www.quadibloc.com/other/asp01.htm
from which you can see just what a mess the field of possible resolutions for computer monitors is. You can learn new facts, such as the fact that "21:9" aspect ratio wide monitors really have an aspect ratio of 21.5 to 9, or 43:18. You can find collected information on the mystery of the Balanced mode.
John Savard
I believe the original LO-res VGA mode was 320x200 (which was not 3:4)
Unsure what DOOM used.. there's ways to get 320x240...
Quadibloc
2021-07-10 20:17:27 UTC
Permalink
Post by Johann Klammer
I believe the original LO-res VGA mode was 320x200 (which was not 3:4)
Unsure what DOOM used.. there's ways to get 320x240...
I've checked, and indeed CGA offered 160x100, 320x200, and 640x200 in
16, 4, and 2 colors respectively, at least according to Wikipedia.

Then EGA extended things...

320x200 and 640x200 on CGA monitors, but 320x350 and 640x350 on
EGA monitors... and 640x350 and 720x350 on MDA monitors.

And indeed it appears you are right: Mode 13h on VGA was 320 by 200,
not 320 by 240. But it did have a 640 by 480 mode with 16 colors, so
one could run Windows 3.1 with it.

John Savard
Quadibloc
2021-07-10 20:30:52 UTC
Permalink
Post by Quadibloc
Post by Johann Klammer
I believe the original LO-res VGA mode was 320x200 (which was not 3:4)
Unsure what DOOM used.. there's ways to get 320x240...
And indeed it appears you are right: Mode 13h on VGA was 320 by 200,
not 320 by 240. But it did have a 640 by 480 mode with 16 colors, so
one could run Windows 3.1 with it.
I've corrected my page. What I forgot was that IBM had the monitors display
25 lines of text, not just 24, so instead of using 10 scan lines per character,
they used 8.

John Savard
Vir Campestris
2021-07-11 20:33:37 UTC
Permalink
Post by Quadibloc
Many TV sets and Blu-Ray players have built-in upscaling features. A similar technology was brought to video cards for gaming by Nvidia with their DLSS; this is on its 2.0 iteration, and in the meantime a simpler technolgy aimed at the same end is now available from AMD with Fidelity FX.
They both have 'Quality' and 'Performance' modes which upscale by 1.5x and 2x respectively.
They also both have a Balanced mode, but Nvidia upscales by 1.72x and AMD upscales by 1.7x.
This piqued my curiosity.
And when I switch resolutions on my monitor, the computer offers me a long list of resolutions. What are these resolutions, what different aspect ratios are associated with them?
Well, my idle curiosity led me to look up some facts which I now present to everyone on the page
http://www.quadibloc.com/other/asp01.htm
from which you can see just what a mess the field of possible resolutions for computer monitors is. You can learn new facts, such as the fact that "21:9" aspect ratio wide monitors really have an aspect ratio of 21.5 to 9, or 43:18. You can find collected information on the mystery of the Balanced mode.
Modern monitors have exactly one native resolution, but can handle other
ones and scale them.

The old CRT ones genuinely could handle different resolutions by
changing the distance between scan lines.

Andy
Quadibloc
2021-07-12 02:44:35 UTC
Permalink
Post by Vir Campestris
Modern monitors have exactly one native resolution, but can handle other
ones and scale them.
The old CRT ones genuinely could handle different resolutions by
changing the distance between scan lines.
Yes, that's quite true. Which is why it's important to know enough about the
resolutions to pick the best one.

Scaling, of course, works best if the monitor's native resolution is a multiple
of the one being scaled from. Thus, a 4K (3840 x 2160) monitor can easily
handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with no loss in sharpness.

John Savard
Ahem A Rivet's Shot
2021-07-12 03:46:38 UTC
Permalink
On Sun, 11 Jul 2021 19:44:35 -0700 (PDT)
Post by Quadibloc
Scaling, of course, works best if the monitor's native resolution is a
multiple of the one being scaled from. Thus, a 4K (3840 x 2160) monitor
can easily handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with no
loss in sharpness.
I think you'll find that the scaling built into modern monitors does
some kind of interpolation rather than just creating blocks the size of the
original pixels.
--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/
Quadibloc
2021-07-12 04:04:05 UTC
Permalink
Post by Ahem A Rivet's Shot
On Sun, 11 Jul 2021 19:44:35 -0700 (PDT)
Post by Quadibloc
Scaling, of course, works best if the monitor's native resolution is a
multiple of the one being scaled from. Thus, a 4K (3840 x 2160) monitor
can easily handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with no
loss in sharpness.
I think you'll find that the scaling built into modern monitors does
some kind of interpolation rather than just creating blocks the size of the
original pixels.
That's true, but if you need to see the individual pixels to read fine text, you will
want to choose resolutions that avoid that.

John Savard
Vir Campestris
2021-07-12 20:49:34 UTC
Permalink
Post by Ahem A Rivet's Shot
On Sun, 11 Jul 2021 19:44:35 -0700 (PDT)
Post by Quadibloc
Scaling, of course, works best if the monitor's native resolution is a
multiple of the one being scaled from. Thus, a 4K (3840 x 2160) monitor
can easily handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with no
loss in sharpness.
I think you'll find that the scaling built into modern monitors does
some kind of interpolation rather than just creating blocks the size of the
original pixels.
Let me give you a really simple example.

I have two pixels, one black (colour 0) and one white (colour 255,
assuming 8 bit).

I want to scale them onto my display which has more pixels, so it will
scale those two pixels into three.

The first will be 0, and the last 255, that's easy.

What will you make the middle one?

Andy
Ahem A Rivet's Shot
2021-07-12 21:39:27 UTC
Permalink
On Mon, 12 Jul 2021 21:49:34 +0100
Post by Vir Campestris
Post by Ahem A Rivet's Shot
On Sun, 11 Jul 2021 19:44:35 -0700 (PDT)
Post by Quadibloc
Scaling, of course, works best if the monitor's native resolution is a
multiple of the one being scaled from. Thus, a 4K (3840 x 2160) monitor
can easily handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with
no loss in sharpness.
I think you'll find that the scaling built into modern monitors
does some kind of interpolation rather than just creating blocks the
size of the original pixels.
Let me give you a really simple example.
Sadly most of the upscaling interpolation algorithms are less than
simple.
Post by Vir Campestris
I have two pixels, one black (colour 0) and one white (colour 255,
assuming 8 bit).
I want to scale them onto my display which has more pixels, so it will
scale those two pixels into three.
Not very realistic - more commonly one pixel becomes four and rather
than making blocks of four pixels the same colour some interpolation is
done based on the surrounding pixels - rather like anti-aliasing text.
--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/
Vir Campestris
2021-07-20 20:27:23 UTC
Permalink
Post by Ahem A Rivet's Shot
On Mon, 12 Jul 2021 21:49:34 +0100
Post by Vir Campestris
Post by Ahem A Rivet's Shot
On Sun, 11 Jul 2021 19:44:35 -0700 (PDT)
Post by Quadibloc
Scaling, of course, works best if the monitor's native resolution is a
multiple of the one being scaled from. Thus, a 4K (3840 x 2160) monitor
can easily handle 1920 x 1080 (2x) or 1280 x 720 (3x) resolutions with
no loss in sharpness.
I think you'll find that the scaling built into modern monitors
does some kind of interpolation rather than just creating blocks the
size of the original pixels.
Let me give you a really simple example.
Sadly most of the upscaling interpolation algorithms are less than
simple.
Post by Vir Campestris
I have two pixels, one black (colour 0) and one white (colour 255,
assuming 8 bit).
I want to scale them onto my display which has more pixels, so it will
scale those two pixels into three.
Not very realistic - more commonly one pixel becomes four and rather
than making blocks of four pixels the same colour some interpolation is
done based on the surrounding pixels - rather like anti-aliasing text.
I'm sure I've seen screens that needed a 2:3 somewhere... where was
it... oh yes, that TV I'm using for a screen.

1280x720 onto 1920x1080 is 3 onto 2


There are other worse ones in common use, such as PAL onto 720.

Andu
Ahem A Rivet's Shot
2021-07-20 20:45:12 UTC
Permalink
On Tue, 20 Jul 2021 21:27:23 +0100
Post by Vir Campestris
I'm sure I've seen screens that needed a 2:3 somewhere... where was
it... oh yes, that TV I'm using for a screen.
1280x720 onto 1920x1080 is 3 onto 2
You're only considering the one dimensional mapping of 1280 onto
1920 not the two dimensional mapping which would likely be four pixels
being mapped onto nine or some more complex mapping.
--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/
Vir Campestris
2021-07-25 20:46:42 UTC
Permalink
Post by Ahem A Rivet's Shot
On Tue, 20 Jul 2021 21:27:23 +0100
Post by Vir Campestris
I'm sure I've seen screens that needed a 2:3 somewhere... where was
it... oh yes, that TV I'm using for a screen.
1280x720 onto 1920x1080 is 3 onto 2
You're only considering the one dimensional mapping of 1280 onto
1920 not the two dimensional mapping which would likely be four pixels
being mapped onto nine or some more complex mapping.
Sure.

But put a horizontal black edge in 720 onto a 1080 screen, and there
will be artefacts as it moves up or down.

Andy
Theo
2021-07-12 17:16:20 UTC
Permalink
Post by Vir Campestris
The old CRT ones genuinely could handle different resolutions by
changing the distance between scan lines.
But you were ultimately limited by the dot pitch of the phosphor. Slot or
shadow masks had a specific X/Y region for each visible pixel. Aperture
grille types had continuous stripes of phosphor so any vertical resolution
was possible (up to the beam spot focus), but horizontal resolution was
still restricted by the pitch of the phosphor stripes.

If you tried to go finer than the dot pitch (eg 0.28mm=90dpi) and the
scanning electronics could handle it, pixels would smear together on the
phosphor.

Theo
Ahem A Rivet's Shot
2021-07-12 18:07:09 UTC
Permalink
On 12 Jul 2021 18:16:20 +0100 (BST)
Post by Theo
Post by Vir Campestris
The old CRT ones genuinely could handle different resolutions by
changing the distance between scan lines.
But you were ultimately limited by the dot pitch of the phosphor. Slot or
shadow masks had a specific X/Y region for each visible pixel.
Monochrome monitors were genuinely analogue, there was no dot pitch
just bandwidth limits on the circuitry and a spot size.
--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/
Quadibloc
2021-07-12 19:18:06 UTC
Permalink
Post by Ahem A Rivet's Shot
On 12 Jul 2021 18:16:20 +0100 (BST)
But you were ultimately limited by the dot pitch of the phosphor. Slot or
shadow masks had a specific X/Y region for each visible pixel.
Monochrome monitors were genuinely analogue, there was no dot pitch
just bandwidth limits on the circuitry and a spot size.
And, in general, color monitors had a dot pitch smaller than the minimum resolution
they could support, since they couldn't control the relationship of the scanning
electron beam to the phosphor dots to produce behavior analogous to what
LCD monitors do.

John Savard
Freddy1X
2021-07-13 02:11:45 UTC
Permalink
Post by Quadibloc
Post by Ahem A Rivet's Shot
On 12 Jul 2021 18:16:20 +0100 (BST)
But you were ultimately limited by the dot pitch of the phosphor. Slot
or shadow masks had a specific X/Y region for each visible pixel.
Monochrome monitors were genuinely analogue, there was no dot pitch
just bandwidth limits on the circuitry and a spot size.
And, in general, color monitors had a dot pitch smaller than the minimum
resolution they could support, since they couldn't control the
relationship of the scanning electron beam to the phosphor dots to produce
behavior analogous to what LCD monitors do.
John Savard
Was a high definition projection color monitor ever made? With 3 non-shadow
masked tubes, your resolution could reach minum dot size. Something that
could be used in an auditorium setting.

Freddy,
just guessing.
--
Warning! Don't use knife to insert & cut the wire. It will hurt PCB
circuit.

/|>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\|
/| I may be demented \|
/| but I'm not crazy! \|
/|<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\|
* SPAyM trap: there is no X in my address *
J. Clarke
2021-07-13 02:45:29 UTC
Permalink
Post by Freddy1X
Post by Quadibloc
Post by Ahem A Rivet's Shot
On 12 Jul 2021 18:16:20 +0100 (BST)
But you were ultimately limited by the dot pitch of the phosphor. Slot
or shadow masks had a specific X/Y region for each visible pixel.
Monochrome monitors were genuinely analogue, there was no dot pitch
just bandwidth limits on the circuitry and a spot size.
And, in general, color monitors had a dot pitch smaller than the minimum
resolution they could support, since they couldn't control the
relationship of the scanning electron beam to the phosphor dots to produce
behavior analogous to what LCD monitors do.
John Savard
Was a high definition projection color monitor ever made? With 3 non-shadow
masked tubes, your resolution could reach minum dot size. Something that
could be used in an auditorium setting.
I presume you mean CRT--movie theaters use 8K projection color
monitors now.

There's a wikipedia page with a list of them:
<https://en.wikipedia.org/wiki/List_of_CRT_video_projectors>
Timothy McCaffrey
2021-07-27 16:55:48 UTC
Permalink
Post by Quadibloc
Many TV sets and Blu-Ray players have built-in upscaling features. A similar technology was brought to video cards for gaming by Nvidia with their DLSS; this is on its 2.0 iteration, and in the meantime a simpler technolgy aimed at the same end is now available from AMD with Fidelity FX.
They both have 'Quality' and 'Performance' modes which upscale by 1.5x and 2x respectively.
They also both have a Balanced mode, but Nvidia upscales by 1.72x and AMD upscales by 1.7x.
This piqued my curiosity.
And when I switch resolutions on my monitor, the computer offers me a long list of resolutions. What are these resolutions, what different aspect ratios are associated with them?
Well, my idle curiosity led me to look up some facts which I now present to everyone on the page
http://www.quadibloc.com/other/asp01.htm
from which you can see just what a mess the field of possible resolutions for computer monitors is. You can learn new facts, such as the fact that "21:9" aspect ratio wide monitors really have an aspect ratio of 21.5 to 9, or 43:18. You can find collected information on the mystery of the Balanced mode.
John Savard
As others have pointed out, CRTs had a "Vertical Size" adjustment. It was not unusual for a piece of graphics software
to draw a circle on the screen and have the user adjust the VS so that it was round (vs. elliptical).

If you adjusted the VS for a 320x200 image so it took up the whole screen the pixels were not "square", if you adjusted VS
so that they were square, a lot of the screen was left blank, and things looked squished together.

And it just got worse with the Hercules card with a monochrome monitor (720x348), and later EGA (640x350), there is no
way you could ever get square pixels. It was a real pain in the neck for programmers doing low level graphics.
Now, you can just assume the pixels are square, and the assume the monitor is shaped weird (e.g. 5120x1440 for a recent
Samsung gaming monitor).

- Tim
Ahem A Rivet's Shot
2021-07-27 17:27:40 UTC
Permalink
On Tue, 27 Jul 2021 09:55:48 -0700 (PDT)
Post by Timothy McCaffrey
As others have pointed out, CRTs had a "Vertical Size" adjustment. It
was not unusual for a piece of graphics software to draw a circle on the
screen and have the user adjust the VS so that it was round (vs.
elliptical).
In the UK at least TV channels broadcast a test card when there
were no programs which would include circles, horizontal and vertical lines
in various places, grey scales and so forth to help installers, repairers
and sometimes even customers set up TVs properly.
--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/
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