On Wed, 9 Jun 2010 17:01:33 +0100, "Ret." xxx wrote:

MC wrote:
-----------------8
At a viewing distance you mention, a 37" TV is not really going to
give you the best HD viewing experience anyway. 42" is really the
minimum to make it worth your while and 40" is pushing it.

Sorry but I have to disagree. I have a Panasonic 37" plasma and view from
around 9'. The HD picture is superb and considerably better than the SD
picture.

I did read an article recently that suggested that many viewers cannot fully
appreciate HD TV simply because their eyesight is not sufficiently acute!

Which is what I would have thought, but the Sony web site has a table
of optimum viewing distances that, to my mind, are astonishingly
short. Who's right?

"Appelation Controlee" wrote in message
...


Which is what I would have thought, but the Sony web site has a table
of optimum viewing distances that, to my mind, are astonishingly
short. Who's right?



i think optimum viewing distances are daft - it's up to you.
my mother thinks a tv should be a tiny thing that dissapears into the corner
of the room, when i watch a movie i want the cinema experience - or as my
father once said ' a big eye staring at you'
horses for courses.

or to put it another way, what;s the point in buying a larger screen and
then sitting further away? - you might as well get a cheaper small one and
sit closer.



--
Gareth.

that fly...... is your magic wand....
http://dsbdsb.mybrute.com
you fight better when you have a bear!

On 09/06/2010 17:01, Ret. wrote:
MC wrote:
George wrote:

Our TV is a Panasonic TH-37PX70B, which you will realise is a 37"
model. It has a max resolution of 720 horizontal pixels so I will
not be getting full 1080 HD. We normally view from between 3-4
metres.

I don't think the picture from the SkyHD box, when viewing SD
channels, is as good as that from the Sky+ box. I do see a
difference between, say, Sky1 and Sky1HD although I feel the picture
is softer than we were used to with the Sky+ box.

Will need to give it a week or so to see if HD is worth the extra
£10/week.

At a viewing distance you mention, a 37" TV is not really going to
give you the best HD viewing experience anyway. 42" is really the
minimum to make it worth your while and 40" is pushing it.

Sorry but I have to disagree. I have a Panasonic 37" plasma and view
from around 9'. The HD picture is superb and considerably better than
the SD picture.

I did read an article recently that suggested that many viewers cannot
fully appreciate HD TV simply because their eyesight is not sufficiently
acute!

....I think that there is a subliminal effect which means that, although
the viewing distance means individual pixels cannot be resolved, the
combined effect is, somehow, enhanced over SD. The whole is greater
than the sum of the parts. (IMO)

--
George from Cartland

On Wed, 09 Jun 2010 18:42:20 +0100, Mike Henry
wrote:

In , Appelation Controlee
wrote:

On Wed, 9 Jun 2010 17:01:33 +0100, "Ret." xxx wrote:

MC wrote:
-----------------8
At a viewing distance you mention, a 37" TV is not really going to
give you the best HD viewing experience anyway. 42" is really the
minimum to make it worth your while and 40" is pushing it.

Sorry but I have to disagree. I have a Panasonic 37" plasma and view from
around 9'. The HD picture is superb and considerably better than the SD
picture.

I did read an article recently that suggested that many viewers cannot fully
appreciate HD TV simply because their eyesight is not sufficiently acute!

Which is what I would have thought, but the Sony web site has a table
of optimum viewing distances that, to my mind, are astonishingly
short. Who's right?

Depends on what the exact wording of the Sony table is! Science tells us
what the absolute maximum detail that the human eye can resolve is if you
have perfect eyesight, 20-20 vision, average eyesight, etc.

You then do your calculations starting there; so first of all (a) you have
a distance that's pretty uncomfortably close where you'll be able to see
each pixel individually.

(b) Then, further away from this is a distance where you can see the
difference between say 1080 and 576 resolutions on the same screen even if
you can't see every pixel of the 1080 picture.

At this point be careful to remember it's hard to compare SD vs HD on the
same display - the bitrates of the channels won't be the same, and even
the size of artefacts are smaller on the HD display if the bitrates are
kept in proportion. Also some TVs do a worse job or displaying SD than an
SD TV which is the same size.

(c) Next, further away from this again is the point where you might as
well have bought a SD display, because you're too far back to even see any
difference between 1080 and 576 resolutions unless you are an eagle, hawk
or a buzzard. Ie it's impossible for human eyesight to detect a difference
at this distance.

Thankfully others have already done the calculations for us, and there is
a chart here you can use:
http://hd.engadget.com/2006/12/09/10...o-screen-size/

If you're at (c) and you've spent a lot of money, past experience on this
group shows that strange denial of scientific facts starts to creep in,
and people start claiming that it's a matter of faith instead of science
:-). So somewhere at the (b) end of the range (b)-(c) is the ideal. You
may be surprised at how close this is.

HTH

Well I'm up for a mathematical challenge... lets throw some numbers at
this.

So the human retina has a certain number of rods and cones that allow
you to perceive an image. Now it's reasonably well known (Google it)
that a screen at 300DPI is as much detail that the human retina can
resolve when held at a distance of 10". In fact, Steve Jobs even
quoted this when he was boasting about the new iPhone 4's "retina
display".

Rather than going into the details of how to calculate angular sizes,
there are a number of online calculators that do this. I used this
one: http://www.1728.com/angsize.htm

300DPI means there are 300 dots per inch, or pixels per inch. So in a
line of pixels on the display there are 300 pixels, or one pixel every
1/300". That's one every 0.0033333 recurring.

If we put 10" and 0.00333333" into the angular size calculator, and
work out the angle, we get 0.019099 Degrees. Using this angle we can
figure out what distance an HD (1920x1080p) TV would need to be of a
given size before your retina physically can't perceive any more
detail.

So let's do this for 32", 37", 42", 46", 52"... as they're pretty
common sizes of TVs.

Those are diagonal sizes, so we use the Pythagorean theorem and the
known ratio of 16:9 to calculate the horizontal size. From the above
sizes we get the following (rounded off) vertical sizes... Also, to
save me typing out more tables we simply divide 1080 (because there
are 1080 vertical pixels on an HD TV) by those values to get the DPI
of the TV. Finally I'll add a column of the height of a pixel by
dividing 1 by the DPI. With me so far? Good...

So in this table we're going TV Size - Vertical Size - DPI - Height
of a pixel.

32" - 15.7" - 68.8dpi - 0.0145"
37" - 18.1" - 59.7dpi - 0.0168"
42" - 20.6" - 52.4dpi - 0.0191"
46" - 22.6" - 47.8dpi - 0.0209"
52" - 25.5" - 42.4dpi - 0.0236"

To be clear, the above table shows the approximate DPI (also called
dot pitch) of TVs of different diagonal sizes. This may differ from
what is stated in the specification of your TV, but I'm talking about
the DPI of 1080 pixels here, not the dot pitch of TV which may well be
the individual R/G/B component sizes or a higher DPI in general. We
also know that the human retina has a resolution limit equivalent to
an angular size of 0.019099 Degrees.

So if we throw the above pixel heights into the angular size
calculator, along with the angular size limit of the human retina, we
get the following TV size to distance limits in inches and rounded off
to the nearest foot:

32" - 43" - 3.6 feet
37" - 50" - 4.2 feet
42" - 57" - 4.8 feet
46" - 63" - 5.2 feet
52" - 71" - 5.9 feet

And what do those distances in feet really mean? Well, it means that
if our TV is further away than that distance, then if we get a bigger
TV we would be able to see more detail. If our TV is closer than that
distance then you're essentially just zooming into pixels so you're
not gaining any more detail. Or to relate back to a previous post, a
37" TV is absolutely fine, in terms of what the human eye can
perceive, at distances up to 4.2 feet. If the TV was moved a further 7
inches away to a total distance of 4.8 feet away then you would see
more detail with a bigger 42" screen.

But, is HD better than SD on a 37" screen at 9 feet? If the TV is
further away than 4.2 feet then the resolution becomes higher than
that what a human eye can perceive. But how would SD appear at that
distance? For argument's sake, lets say SD is 576 pixels high. On a
37" screen that's 576 pixels across 18.1", so the height of a pixel is
0.0314", which gives a cut-off distance of 94", or 7.8 feet. So, in
fact, at 9 feet distance, an SD screen at 576 pixels would look no
better than an HD screen at that distance. Your 37" TV would have to
be closer than 7.8 feet to start seeing a difference. But you said you
DID see a difference, which means it was entirely down to the higher
bitrates and different codecs that made the image look better. The
bottom line is, that at 9 feet distance, the human eye can't even
perceive the individual pixels of SD resolution on a 37" TV, let alone
HD. But codecs, bitrates, cables, etc, all come into play here.

In conclusion, if you want to buy a 1080p HD TV based on what a human
eye with perfect vision can perceive at a given distance, and you
don't want to take bitrates, compression, codecs, cabling, etc into
account, then use the table below. Anything bigger and you're wasting
money, anything smaller and you won't be able to see all the detail.

TV size - Viewing Distance
32" - 43" (3.6 feet)
37" - 50" (4.2 feet)
42" - 57" (4.8 feet)
46" - 63" (5.2 feet)
52" - 71" (5.9 feet)

Interestingly, my calculations seem pretty close to the linked page,
so I guess there's some truth to them.

--
Vincent

"Mike Henry" wrote in message
...
In , Vincent
wrote:

Well I'm up for a mathematical challenge... lets throw some numbers at
this.

[big snip of great stuff]

Top work! You could have found the Dec thread too but I guess you like
doings maths for fun :-)

In conclusion, if you want to buy a 1080p HD TV based on what a human
eye with perfect vision can perceive at a given distance, and you
don't want to take bitrates, compression, codecs, cabling, etc into
account, then use the table below. Anything bigger and you're wasting
money, anything smaller and you won't be able to see all the detail.

TV size - Viewing Distance
32" - 43" (3.6 feet)
37" - 50" (4.2 feet)
42" - 57" (4.8 feet)
46" - 63" (5.2 feet)
52" - 71" (5.9 feet)

Interestingly, my calculations seem pretty close to the linked page,
so I guess there's some truth to them.

Either that or you got the calculations right :-). Yes this was previously
covered by John Legon and Andy Champ in a thread here last December. (See
http://groups.google.com/group/uk.te...-8&oe=utf-8&q=
)
At the time I plugged in my figures for a viewing distance of 3m for
1080p, and got a screen size of 75" - which matched the engadget.com chart
nicely. I've linked to it since as it's handy and shows different
distances for 1080p and 720p, and you can easily check if you are sitting
in the "zones" between the lines. As you say, if you're too far away (eg
you have a 1080p panel but you sit in the green or blue zones on the
chart), then you're wasting money.



One thing forgotten in all this is TV is an optical illusion. No 2 people
will see exactly the same thing because of this.

Gary

"Gary" wrote in message
news:nElQn.7252$1b3.5805@hurricane...

"Mike Henry" wrote in message
...
In , Vincent
wrote:

Well I'm up for a mathematical challenge... lets throw some numbers at
this.

[big snip of great stuff]

Top work! You could have found the Dec thread too but I guess you like
doings maths for fun :-)

In conclusion, if you want to buy a 1080p HD TV based on what a human
eye with perfect vision can perceive at a given distance, and you
don't want to take bitrates, compression, codecs, cabling, etc into
account, then use the table below. Anything bigger and you're wasting
money, anything smaller and you won't be able to see all the detail.

TV size - Viewing Distance
32" - 43" (3.6 feet)
37" - 50" (4.2 feet)
42" - 57" (4.8 feet)
46" - 63" (5.2 feet)
52" - 71" (5.9 feet)

Interestingly, my calculations seem pretty close to the linked page,
so I guess there's some truth to them.

Either that or you got the calculations right :-). Yes this was
previously
covered by John Legon and Andy Champ in a thread here last December. (See
http://groups.google.com/group/uk.te...-8&oe=utf-8&q=
)
At the time I plugged in my figures for a viewing distance of 3m for
1080p, and got a screen size of 75" - which matched the engadget.com
chart
nicely. I've linked to it since as it's handy and shows different
distances for 1080p and 720p, and you can easily check if you are sitting
in the "zones" between the lines. As you say, if you're too far away (eg
you have a 1080p panel but you sit in the green or blue zones on the
chart), then you're wasting money.



One thing forgotten in all this is TV is an optical illusion. No 2 people
will see exactly the same thing because of this.

Gary



My eyes have been tested and I have better than 20/20.
My wife can see small things further away than I can IE her resolution is
better than mine.

I asked the optician how can i get my eyesight to be better than hers . Get
a new wife was the answer!

Gary