[opendtv] Re: 4k @ 60 fps encoded into 15 Mbps using HEVC
- From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 21 Oct 2012 09:33:49 -0400
On 10/21/2012 7:57 AM, Olivier Houot wrote:
Hi Mark,
just implicitely using the usual average 30 cycles per degree acuity.
"Usual" is correct; "average" might not be. Even Snellen in 1862
recognized both greater visual acuity and a contrast sensitivity. Based
on the contrast-sensitivity function, we might be insensitive to detail
at 30 cpd unless it has huge contrast, and few displays can offer huge
pixel-to-pixel contrast even were lenses and cameras able to deliver it.
I find it interesting that, as we enter into a new era of displays,
almost no one is doing tests on what we can see (NHK's acuity tests on
their subjects, prior to their tests of displays, showed a high-contrast
acuity of roughly 60 cpd, not 30).
Of course, this is an average
Is it? How do we know this? I've been looking for modern references
(and, as I noted, even the old Snellen didn't say it was average).
I am not sure why you mention presbyopic viewers, though ? Those only have
problems for viewing things close up, right? Since you are still a few meters
away from the screen this should not come into play.
In the U.S., 30-cpd acuity is described as 20/20, the 20 referring to a
viewing distance in feet. Elsewhere, it is 6/6, the 6 referring to a
viewing distance in meters. THOSE distances are where
focus-accommodation issues may be ignored. Your previously-mentioned
six-foot viewing distance is only a third of the way there.
Viewing distance, incidentally, is another issue that hasn't been
studied in quite some time (since Lechner and Jackson, and even they
just did informal surveys). There is a place in the UK called the 1-3-9
Media Lab, which studies consumer viewing. The numbers refer to the
nominal supposed viewing distances (in feet) of hand-held devices, other
computer screens, and TV screens. But the lab's head, Sarah Pearson,
notes that, for TV viewing in particular, distances for the same viewer
and display can change substantially between laid-back relaxation and
edge-of-seat interest.
I like to think the powers-of-three progression of the lab name can be
extended to 27 for stadium-seating cinema and 81 for IMAX, which brings
me to your response to Mike Tsinberg:
Even though you might finally get the same angular size, depending on where you
seat, there is that feeling of a big room and screen, which is
not quite the same at home.
I agree, except that I would drop the "quite." Aside from any issues
associated with visual perception, there are MANY other factors
differentiating cinema from even a dark home theater. Two worth
considering are crowd behavior and cognitive dissonance.
As to crowd behavior, I highly recommend viewing "The Psychological
Experiments," available on video. In one of the experiments, there are
tasks to be performed in a room by either one or three people. Smoke
enters the room under a doorway. When there is one subject, invariably
that person alerts the experimenters to the smoke. When there are
three, there is usually no alert, the theory seemingly being, "Well, if
no one else is concerned, why should I be?"
It seems to be this group behavior mentality that has audiences for the
Metropolitan Opera live cinema transmissions applauding in their remote
auditoriums, where there are no performers to hear them. I've checked
press reports for a 1952 cinema transmission, and they did it then, too.
As to cognitive dissonance, watching a movie (or opera) in a cinema
requires a financial outlay for a ticket, travel to the cinema, blocking
out time, and possibly such other costs/requirements as getting a baby
sitter, parking/transit fees, dinner, etc. If, after all of that, the
viewer doesn't like the movie, then all of the expenditures of money and
time were foolish. But the viewer doesn't want to be a fool, so there
is a predisposition to like the event.
It is my personal theory that such cognitive dissonance helps explain
the difference in societal regard for movies vs. television: that movies
are an art but TV is not, that the Oscars are significant but the Emmy
awards are not, etc.
TTFN,
Mark
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