# Font type and size was (QVGA V/s VGA for GTA03)

Dr. H. Nikolaus Schaller hns at computer.org
Tue Jun 17 09:22:25 CEST 2008

```This inspires me to do a different calculation based on biological and
physical facts:

According to (German) Wikipedia http://de.wikipedia.org/wiki/Auflösungsvermögen
the human eye can separate two distinct points if they are displaced
in an angle of 2' (2 minutes, i.e. 0.0333 degrees). For lines and
structures the resultion is up to 0.3' (i.e. 0.005 degrees).

Now, if you hold the display in distance of 40cm from your eyes (half
arm-length), this translates to (40cm * tan(0.03333 deg)) 0.02 cm,
i.e. 0.2 mm to see separate points.

On a display with 4.5 x 6 cm this means it should have at least 225 x
300 pixels ~ 130 dpi. QVGA.

But stop - to see separate points, you must have one that is on, then
one that is off and again one that is on. I.e. you need twice the
pixel density or you would simply have a homogenous surface!

=> 450 x 600 pixels ~ 260 dpi i.e. VGA

Now, the 2' was to distinguish two single white spots on an otherwise
black background. The lines and structure resolution of our eyes and
our image processing unit is much better. So, more than VGA is
definitively seen as better by most people (or they need new glasses).

Antialiasing just does a low-pass filter on the image so that the eye
is not so much disturbed by the rasterization of the pixels.

Conclusion:
* QVGA is much worse than the precision of the human eye, so I would
assume most people can read a better display
* Antialiasing does not improve the information content, it just
smoothens the edges
* VGA appears to match the precision to see two separated dots
* >VGA would still be observed as superior
* Antialiasing is no longer required if we go to approx. 1200 x 1500
pixels ~650 dpi on a 2.8 '' display in a distance of 40cm. This is the
biophysical limit where improved resultion becomes invisible. If you
hold it closer (with appropriate glasses or young eyes) you will still
be able to see pixels.

Finally let's try a look into the future: in 10 years such high
resolution displays may be available (e-book!) since the display
manufacturers already know this and work towards the limits.

But since all the discussion wasn't about quality but display and CPU
cost this is not important...

Nikolaus

Am 17.06.2008 um 07:17 schrieb Hans L:

> On Tue, Jun 10, 2008 at 8:59 PM, Dale Schumacher
> <dale.schumacher at gmail.com> wrote:
>> If your current display is around 150dpi, you can see what QVGA
>> would be
>> like with something like this:
>>
>> xterm -fn '*-clean-*--6-*-c-40*' &
>>
>> This will give you a terminal window with a 4x6 font cell (3x5 for
>> characters + 1px spacing).  Note that the automatic "smear bold"
>> make this
>> font unreadable, but the non-bold works.
>>
>> However, I would much prefer to use a larger font on a VGA-size
>> display with
>> 285dpi, like this:
>>
>> xterm -fn '*-clean-med*--16-*-c-80-*' -fb '*-clean-bold*--16-*-c-80-
>> *' &
>>
>
> I think that in order to most accurately simulate the viewing
> experience of a handheld device, ideally you want to show the same
> number of pixels in a particular angle of view.
> Since the pixels per inch of the GTA display are most likely not the
> same as your computer monitor, you can adjust this effective angle of
>
> After some wikipedia and a little arithmetic, I think that the
> situation can be simplified to the following equation:
>
> Dcm =  Dhh * PPIhh / PPIcm
>
> Dcm = viewing distance of computer monitor
> Dhh = viewing distance of hand-held device
> PPIhh = Pixels Per Inch of hand-held device
> PPIhh = Pixels Per Inch of computer monitor
>
> I held up my current phone, as if I was about to type something on the
> keypad, and determined that a comfortable position for me is to hold
> my phone roughly 12" in front of my eyes.
>
> The GTA02 device has 640 pixels along it's longest dimension of 2.27".
> 640 / 2.27 is about 282 PPI
> The monitor I'm using right now has 1024 pixels on its horizontal, and
> is 12" wide, which comes to about 85 pixels per inch.
>
> So, in order to simulate the GTA02 displaying VGA xterm at 12"
> viewing distance:
>
> 12" * 282ppi / 85ppi = about 40"
>
> I can then view this command from 40" away from my monitor:
>> xterm -fn '*-clean-med*--16-*-c-80-*' -fb '*-clean-bold*--16-*-c-80-
>> *' &
>
> ...and it will theoretically take up the same field of view as a (VGA)
> GTA02 at 12"
>
> To compare with a same sized QVGA screen, view at half distance as
> previous command(20" for me):
>> xterm -fn '*-clean-*--6-*-c-40*' &
>
> Disclaimer: I'm certainly no expert in visual perception or optics,
> and even my geometry is a little rusty, so please correct me if any of
> this doesn't make sense.
>
> So, with the geeky number crunching out of the way, my conclusion to
> this experiment is that I find that (my simulated version of) 640x480
> on a 2.27" screen is very readable at 80x24, and very useful (to my
> eyes anyways).
>
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