I am the author of an Apple II emulator; I recently received a bug report that its pixels aspect ratio is off — e.g. in text mode, pixels are not square.

I checked the arithmetic on that and the emulator's workings seems to be correct that vanilla NTSC would produce pixels around 93% as wide as tall.

But then I also took a look at photographic evidence of Apple IIs paired with appropriate monitors and indeed the few of those that are appropriately framed to be able to take measurements from appear to show square pixels*.

Can anyone give me a sense of the probability distribution here? How common was it to calibrate an Apple II's display to try to make the pixels square? Am I even right to think they wouldn't be square on a television?

* E.g. this one of Mouse Desk: https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from which I measured the aspect ratio of the desktop and compared to the aspect ratio when output at around the 93% number as shown above; the photograph was roughly 8% wider.

In article <4e09a85b-bd8f-40f5-8c04-b9c9704708f9n@googlegroups.com>,
Thomas Harte <thomas.harte@gmail.com> wrote:
>I am the author of an Apple II emulator; I recently received a bug
>report that its pixels aspect ratio is off — e.g. in text mode, pixels
>are not square.
>
>I checked the arithmetic on that and the emulator's workings seems to be
>correct that vanilla NTSC would produce pixels around 93% as wide as
>tall.
>
>But then I also took a look at photographic evidence of Apple IIs paired
>with appropriate monitors and indeed the few of those that are
>appropriately framed to be able to take measurements from appear to show
>square pixels*.
>
>Can anyone give me a sense of the probability distribution here? How
>common was it to calibrate an Apple II's display to try to make the
>pixels square? Am I even right to think they wouldn't be square on a
>television?
>
>* E.g. this one of Mouse Desk:
>https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from
>which I measured the aspect ratio of the desktop and compared to the
>aspect ratio when output at around the 93% number as shown above; the
>photograph was roughly 8% wider.

I think it was possible to use monitors with square pixels, and some people
may have done so intentionally, since monitors/TVs of this time often had
adjustments to stretch/squeeze the image horizontally and vertically. Some
companies may have taken care to adjust their monitors in their photos to get
square pixels. Note that your sample photo does not have equidistant
borders--the horizontal visible region is compressed, and the vertical
stretched, relatively, looking at the border regions (the side borders are
larger than the top/bottom borders). It would be interesting to look at a
photo of the //c LCD display (which cannot be adjusted) to see if that has
square pixels. I believe it does not, and is very squished.

But in general, I would not expect much software to rely on it since your
average TV would not be set up to give you square pixels.

It was a selling point of the Mac in 1984 that Apple guaranteed square
pixels there (since the PC world has a wild and crazy place). Since your
photo has a mouse, that means it is post 1984, so the taker of the photo may
have tried to make the Apple IIe subtly look more like a Mac. That's very
understandable from a marketing perspective.

Kent

Thomas Harte wrote:
> I am the author of an Apple II emulator; I recently received a bug report
> that its pixels aspect ratio is off — e.g. in text mode, pixels are not
> square.
>
> I checked the arithmetic on that and the emulator's workings seems to be
> correct that vanilla NTSC would produce pixels around 93% as wide as tall.
>
> But then I also took a look at photographic evidence of Apple IIs paired
> with appropriate monitors and indeed the few of those that are
> appropriately framed to be able to take measurements from appear to show
> square pixels*.
>
> Can anyone give me a sense of the probability distribution here? How
> common
> was it to calibrate an Apple II's display to try to make the pixels
> square?
> Am I even right to think they wouldn't be square on a television?
>
> * E.g. this one of Mouse Desk:
> https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from
> which I measured the aspect ratio of the desktop and compared to the
> aspect
> ratio when output at around the 93% number as shown above; the photograph
> was roughly 8% wider.
>

Thomas Harte wrote:
> I am the author of an Apple II emulator; I recently received a bug report
> that its pixels aspect ratio is off — e.g. in text mode, pixels are not
> square.
>
> I checked the arithmetic on that and the emulator's workings seems to be
> correct that vanilla NTSC would produce pixels around 93% as wide as tall.
>
> But then I also took a look at photographic evidence of Apple IIs paired
> with appropriate monitors and indeed the few of those that are
> appropriately framed to be able to take measurements from appear to show
> square pixels*.
>
> Can anyone give me a sense of the probability distribution here? How
> common
> was it to calibrate an Apple II's display to try to make the pixels
> square?
> Am I even right to think they wouldn't be square on a television?
>
> * E.g. this one of Mouse Desk:
> https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from
> which I measured the aspect ratio of the desktop and compared to the
> aspect
> ratio when output at around the 93% number as shown above; the photograph
> was roughly 8% wider.
>

I really doubt that you can get a definitive answer on this. I enjoy
converting graphics to Apple II formats and I have tried to figure out some
rule about this, but they all have some caveats.

You would assume that someone with a 4:3 Monitor would like to use the whole
screen real state to display full-screen graphics, so they would adjust the
visible area to leave symmetric borders for both axis. In that case the
aspect ratio in HiRes would be about 91,4%.

The Apple IIe Card for the Mac LC uses this aspect ratio as well. For
example, when installed on a Color Classic, the monitor would switch its
native resolution of 512x384 to 560x384 to make room for the full resolution
in 80 cols and DHGR. By doing so, it would stretch the pixels to exactly
32:35.

But this does not seem to be the common assumption. For example the Analog
Clock from AE assumes an aspect ratio of 83%, see
https://macgui.com/spyglass/r/0ed4df212b04180a/ANALOG.CLOCK?f=DmNtZWlpYAZqZmRvZg&fk=af3627ab31
This looks vertically squashed on every system I tried, so I wonder if
anyone ever adjusted their screen to see this as a circle.

My PAL Apple //c using the color adapter and connected to a relatively
modern PAL TV without position controls fixes the aspect ratio to ~1,114 and
leaves an uncentered image with unsymmetrical borders.

I don't think that the MouseDesk Screenshot is a good example. First, it is
a modern mock-up. Second, Mouse Desk uses the Monochrome DHGR resolution of
560x192 which produces tall pixels, not square pixels.

Anyway, I think that it might be a good idea if the emulator could allow to
select the 1:1 pixel ratio as a non-default option.

Just a side question... how do I swap disks on your emulator? I have not
been able to use multi disk programs with it. Am I missing something?

cybernesto <cybernesto@macgui.com> wrote:
> Thomas Harte wrote:
>> I am the author of an Apple II emulator; I recently received a bug report
>> that its pixels aspect ratio is off — e.g. in text mode, pixels are not
>> square.
>>
>> I checked the arithmetic on that and the emulator's workings seems to be
>> correct that vanilla NTSC would produce pixels around 93% as wide as tall.
>>
>> But then I also took a look at photographic evidence of Apple IIs paired
>> with appropriate monitors and indeed the few of those that are
>> appropriately framed to be able to take measurements from appear to show
>> square pixels*.
>>
>> Can anyone give me a sense of the probability distribution here? How
>> common
>> was it to calibrate an Apple II's display to try to make the pixels
>> square?
>> Am I even right to think they wouldn't be square on a television?
>>
>> * E.g. this one of Mouse Desk:
>> https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from
>> which I measured the aspect ratio of the desktop and compared to the
>> aspect
>> ratio when output at around the 93% number as shown above; the photograph
>> was roughly 8% wider.
>>
>
> Thomas Harte wrote:
>> I am the author of an Apple II emulator; I recently received a bug report
>> that its pixels aspect ratio is off — e.g. in text mode, pixels are not
>> square.
>>
>> I checked the arithmetic on that and the emulator's workings seems to be
>> correct that vanilla NTSC would produce pixels around 93% as wide as tall.
>>
>> But then I also took a look at photographic evidence of Apple IIs paired
>> with appropriate monitors and indeed the few of those that are
>> appropriately framed to be able to take measurements from appear to show
>> square pixels*.
>>
>> Can anyone give me a sense of the probability distribution here? How
>> common
>> was it to calibrate an Apple II's display to try to make the pixels
>> square?
>> Am I even right to think they wouldn't be square on a television?
>>
>> * E.g. this one of Mouse Desk:
>> https://www.oldcomputr.com/wp-content/uploads/2015/12/apple_iie.jpg from
>> which I measured the aspect ratio of the desktop and compared to the
>> aspect
>> ratio when output at around the 93% number as shown above; the photograph
>> was roughly 8% wider.
>>
>
> I really doubt that you can get a definitive answer on this. I enjoy
> converting graphics to Apple II formats and I have tried to figure out some
> rule about this, but they all have some caveats.
>
> You would assume that someone with a 4:3 Monitor would like to use the whole
> screen real state to display full-screen graphics, so they would adjust the
> visible area to leave symmetric borders for both axis. In that case the
> aspect ratio in HiRes would be about 91,4%.
>
> The Apple IIe Card for the Mac LC uses this aspect ratio as well. For
> example, when installed on a Color Classic, the monitor would switch its
> native resolution of 512x384 to 560x384 to make room for the full resolution
> in 80 cols and DHGR. By doing so, it would stretch the pixels to exactly
> 32:35.
>
> But this does not seem to be the common assumption. For example the Analog
> Clock from AE assumes an aspect ratio of 83%, see
> https://macgui.com/spyglass/r/0ed4df212b04180a/ANALOG.CLOCK?f=DmNtZWlpYAZqZmRvZg&fk=af3627ab31
> This looks vertically squashed on every system I tried, so I wonder if
> anyone ever adjusted their screen to see this as a circle.
>
> My PAL Apple //c using the color adapter and connected to a relatively
> modern PAL TV without position controls fixes the aspect ratio to ~1,114 and
> leaves an uncentered image with unsymmetrical borders.
>
> I don't think that the MouseDesk Screenshot is a good example. First, it is
> a modern mock-up. Second, Mouse Desk uses the Monochrome DHGR resolution of
> 560x192 which produces tall pixels, not square pixels.
>
> Anyway, I think that it might be a good idea if the emulator could allow to
> select the 1:1 pixel ratio as a non-default option.

My assumption regarding Apple II display geometry is that it was designed
to be used with a TV monitor which was correctly adjusted for use as a TV.
Nothing in the setup instructions referred to making width or height
adjustments for use with the computer.

But given that many TVs were improperly adjusted, not set up with a test
pattern (remember those?), it’s safe to assume that in practice the pixel
“shape” covered a wide range of possibilities.

On my properly adjusted color TV, hires pixels were noticeably narrower
than they were high, as might be expected when using only 2/3 of the raster
width for 280 pixels, and about 4/5 of the raster height for 192 pixels.

When I wrote hires programs that displayed circles, I always put in a
multiplicative factor for the X coordinate to produce a reasonable replica
of a circle. An X scale factor of about 1.06 produced pleasing
“circularity”. ;-)

If a hard copy was printed, the mapping to printer “pixels” required a
different X scale factor, dependent, of course, on the printer used.

Since the Apple II was never designed to have square pixels, it seems a bit
silly to try to impose that after the fact. If you adjust your monitor to
produce square Apple II pixels, all of your programs will display
incorrectly on others’ machines and when printed.

So just accept that Apple II graphics preceded the desire for square pixels
and program in a scale factor to make things look the way you want on a
monitor properly adjusted for TV.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

On Monday, June 7, 2021 at 8:20:18 AM UTC-7, Thomas Harte wrote:
> I am the author of an Apple II emulator; I recently received a bug report that its pixels aspect ratio is off — e.g. in text mode, pixels are not square.

AppleWin developer here.

I've never known any Apple 2's using a TVs or Apple monitors to have 1:1 aspect ratio (AR). The consensus is that a 4:3 AR is the de facto standard.

Using pixels, 280/192 = 1.45... which "roughly" matches 4:3 = 1.333.

If you draw a circle you will need to use scaling to have it display without it looking like an ellipse.

We had a thread about this back in 2017 called: Emulator aspect ratios?
* https://groups.google.com/g/comp.emulators.apple2/c/YUsAV1BX1Ks

At the time I posted this information: (There was a bug in the original code, here is the fixed version)

# Code

HGR
CALL-151
c051 n c054
2000:7f
2027:7f
3fd0:7f
3ff7:7f
c050 n c052

# Measurements

Apple Color Monitor
==================Width: 9.5"
Height: 7"
Diagonal: 12"

Franklin Color Monitor
=====================Width: 9" or 22.5 cm
Height: 6.5" or 16.5 cm
Diagonal: 11"
Aspect Ratio (Width/height):

# Calculations

Apple:
DPI Width: 560 dots/9.5 inches = 58.94 dpi
DPI Height: 192 dots/7 inches = 27.42 dpi
Aspect Ratio (Width/Height): 9.5 / 7 = 1.35

Franklin:
DPI Width: 560 dots/9 inches = 62 dpi
DPI Height: 192 dots/6.5 inches = 29.58 dpi
Aspect Ratio (Width/Height): 9 / 6.5 = 1.38

Ergo, the aspect ratio is very close to 4/3 = 1.33.

Hope this helps.

m.