[opendtv] Re: (No Date: Tue, 28 Sep 2004 10:30:37 -0400

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 2 Nov 2004 19:18:53 -0500

Cliff Benham wrote:

> I forgot to include this refrence :
> http://www.cse.wustl.edu/~pless/omnivisFinal/nagahara.pdf
> It includes some visualizations of the human field of
> view.
>
> http://www.hitl.washington.edu/publications/r-95-5/

Cliff, thanks for these links. (The third one didn't work
after two attempts at reconstructing the URL.)

Both of these sites are great, but neither really answers
the question of what aspect ratio a screen should be to
look good. The idea of an enveloping helmet is different
from a screen sitting some distance away.

However, I think the information is very useful to
determine what we want to know.

The first link shown above concluded that 180 deg h and
60 deg v are feasible for this helmet device and are the
right answer. The second link used 105 deg h by 40 deg v
to show that more width provided more realism.

How does this translate to what a screen aspect ratio
should be? My claim is the screen should be quite wide
compared to its height. Easily beyond 16:9. Why?

Let's start with a 40" 16:9 screen, sitting 10 ft from
the viewer. And let's assume the field of view of the
viewer is a useful 180h X 60v degrees to start, then
180h X 120v to make Craig happy. Either way, what
screen aspect ratios look better?

A 40" 16:9 screen is about 20" high by 35" wide. At a
distance of 120", this screen fills up 16.6 deg of
horizontal field of view and 9.5 deg vertically. Is
that good?

Well, if our horizontal should be 180 deg, we are
seeing 180 - 16.6 or 163.4 deg of distraction
horizontally.

Vertically, using their 60 deg desired figure,
distraction is limited to 60 - 9.5 or 50.5 deg of
vertical distraction.

So clearly, 16:9 is not nearly wide enough. There's
way much more distraction in the horizontal.

But we actually see more like 120 deg vertically, so
does that change anything? 120 - 9.5 is 110.5 deg,
still MUCH less than 163.4 degrees of horizontal
distraction.

So either way, the 16:9 screen is not wide enough.
Because distraction on the two sides is far greater
than top and bottom.

Okay, let's try a 50" 3:1 screen then. Pretty radical,
right?

A 50" 3:1 screen measures about 47" h and 16" v. At
the same 120" viewing distance, 22.2 degrees h and
7.6 deg v are filled up with image. Even using the
worst-case 120 deg vertical coverage, you still
have 157.8 deg of horizontal distraction vs only
112.4 deg of vertical distraction. So even using
Craig's preference for vertical coverage, the 3:1
screen is still too narrow.

For practical reasons, and to minimize the width
of annoying black bars, it seems logical to go for
something that best approximates the majority of
movie and (new) TV content. It seems to me that
16:9 is a good compromise. Certainly, 4:3 is NOT.

By the way, lost in all of this was John Golitsis'
observation, some time ago, that in his store,
when he would place signs up high, even if within
view, people would IGNORE them. Like they weren't
there. This too should be a clue that vertical
coverage is less important than horizontal
coverage.

Bert
 
 
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