# Re: Making pt a non-physical unit

```On Jan 16, 2010, at 2:48 AM, Giuseppe Bilotta <giuseppe.bilotta@gmail.com
> wrote:

> On Sat, Jan 16, 2010 at 10:39 AM, Ambrose LI <ambrose.li@gmail.com>
> wrote:
>> 2010/1/16 Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
>>>
>>> If print vs screen is to be considered, I'd rather see it influence
>>> whether viewing distance should be considered or not, where print
>>> sizing would be unaffected by (assumed) viewing distance, in
>>> contrast
>>> with screens and projections, where an estimate of the viewing
>>> distance can be done from the device size (an information typically
>>> available from the o/s). For example, an iPhone with a 160dpi (=5/3
>>> the CSS dpi) is usually held a 3/4 the distance of a typical
>>> monitor,
>>> thus leading to a 1.25 (rounded to 1) correspondence between CSS and
>>> actual dpi.

Don't some Android phones have more pixels, but for a similar range of
typical viewing? Wouldn't a Kindle be held at a similar distance, but
with a larger screen and different pixel sizes?

>>
>> But how do you estimate the viewing distance, even if only
>> approximate, for projections? In a large lecture hall or meeting
>> room,
>> it would be a very large range, say 2–50 metres (from the first ro
>> w to
>> the back row). Such estimates are useless.
>
> People sitting at extreme positions are going to have suboptimal
> viewing experiences regardless. So the question would rather be: what
> is the typical 'optimal' viewing distance for a projection with a 100"
> diagonal?

There may be a minimum distance to avoid having large device pixels
from looking like mosaic tiles. But I think it is a "fool's errand" to
try to pick an optimal distance. There is not neccessarily only one
sweet spot, even if you know the size of the screen or projection.
Some displays (of maps, for instance, and not neccesarily just
geographic maps) could be designed to have useful levels of
information at many distances. A billboard or outdoor signage might be
designed to convey the message from a mile away or a hundred feet
away, equally well. It might even have smaller print near the bottom
for when you are close, and huge letter above that for when you are
far away. It might even use some sort of lenticular technology to
changed, without the device size ever changing. Or two billboards of
equal height could have two very different widths, but similar ranges
of good viewing.

Consider also a long hallwall, with the walls covered in a wallpaper-
like OLED. On one side, the display is from floor to ceiling, and the
other side has some chairs and cabinets and so starts from 4 feet up
to ceiling. I use DIVs and CSS animation and a little JavaScript to
move infographics and art and advertising around as you walk down the
hallway.  What does the display size tell you about the optimal
viewing distance? Nothing. I might have smaller, detailed info at head
level, and big arrows or background images at farther distances, way
down there by those two doors at the end.
```

Received on Saturday, 16 January 2010 19:29:36 UTC