dynamic contrast vs. static contracts

Sony claims ( I'm going from memory ) that the static contrast of
their xbr2 is 1300:1 but with a dynamic contrast 7500:1..

What does this mean in actual use... if you compare a real 7500:1 tv
against the sony in different conditions ( dark room, medium room,
light room).. will the 7500:1 look better... or will the human eye
just not be able to tell because of pupil dilation from light level..

Also one more question - comcast has so called "HD" channels but if
you display some of them on a 1080p TV they show up as a box in the
middle of the screen with a border around the box ( on my tv border is
maybe 6 inches ). In the border is says "HD" I think from memory and
border is mainly black. Is this because they do not want to scale the
image to full size as it will distorted ? To me it is pretty annoying
having this border with HD in it - I would rather the border just be
black. Would the same thing happen on a 1080 * 768 tv... ? Or would
the pic then fill the whole screen... ?

Also another question... 3 questions in one here... I bought my TV and
there is an analog/digital button on the remote - you can switch
between the two signals. In digital mode the channels show up with
decimal points like "88.7" etc. What is going on here.. do I have
digitial cable or not ? This went away after the comcast guy
installed the comcast hd receiver box and set it up... I am wondering
what the hd box is using.. analog or digital.. ?

Thanks.

On 2007-03-07, asdf wrote:
Sony claims ( I'm going from memory ) that the static contrast of
their xbr2 is 1300:1 but with a dynamic contrast 7500:1..

What does this mean in actual use... if you compare a real 7500:1 tv
against the sony in different conditions ( dark room, medium room,
light room).. will the 7500:1 look better... or will the human eye
just not be able to tell because of pupil dilation from light level..

Advertised contrast ratios are usually considered bogus. Actual tested values
are often in the low to mid hundreds.

ANSI static contrast ratio is the useful number (when done by a independent
lab): difference between maximum black and white on a checkerboard pattern.

See: http://en.wikipedia.org/wiki/Contrast_ratio

-Bill
--
Sattre Press In the Quarter
http://sattre-press.com/ by Robert W. Chambers
http://sattre-press.com/itq.html

On 7 Mar 2007 21:28:26 GMT, Bill McClain
wrote:

On 2007-03-07, asdf wrote:
Sony claims ( I'm going from memory ) that the static contrast of
their xbr2 is 1300:1 but with a dynamic contrast 7500:1..

What does this mean in actual use... if you compare a real 7500:1 tv
against the sony in different conditions ( dark room, medium room,
light room).. will the 7500:1 look better... or will the human eye
just not be able to tell because of pupil dilation from light level..

Advertised contrast ratios are usually considered bogus. Actual tested values
are often in the low to mid hundreds.


Agreed.
Add also some ambient light falling on the screen and the black level
on the more reflective types get drastically increased.

ANSI static contrast ratio is the useful number (when done by a independent
lab): difference between maximum black and white on a checkerboard pattern.

Yes a minimum momentary contrast is needed for picture quality,
although there is a useful side to dynamic light level control (such
as an iris control or back light control). The black level is not so
critical and can still look black as long as a part of the scene is
bright.

It is in overall dark scenes a better black level is useful.
But there can easily be problems with dynamic light level control, so
better momentary contrast ratio would of course be better.

/Jan

On Mar 7, 10:12 am, "asdf" wrote:
Sony claims ( I'm going from memory ) that the static contrast of
their xbr2 is 1300:1 but with a dynamic contrast 7500:1..

What does this mean in actual use... if you compare a real 7500:1 tv
against the sony in different conditions ( dark room, medium room,
light room).. will the 7500:1 look better... or will the human eye
just not be able to tell because of pupil dilation from light level..


Others had better things to say about this than me.

Also one more question - comcast has so called "HD" channels but if
you display some of them on a 1080p TV they show up as a box in the
middle of the screen with a border around the box ( on my tv border is
maybe 6 inches ). In the border is says "HD" I think from memory and
border is mainly black. Is this because they do not want to scale the
image to full size as it will distorted ? To me it is pretty annoying
having this border with HD in it - I would rather the border just be
black. Would the same thing happen on a 1080 * 768 tv... ? Or would
the pic then fill the whole screen... ?


It sounds like the TV is not scaling the picture, or you are not
watching HD content. Is your set a 16:9 ratio one? OR This could be
because the cable box is not sending the correct signal to your TV
(i.e. the TV needs 1080, but it gets 720, or 480 even). Not sure what
you mean by "...on a 1080 * 768 tv", Do you mean a different screen
ratio (widescreen vs. normal), or do you mean a higher/lower
resolution screen (1080p vs 720p).
On my parents Sony HD tube (direct-view CRT), you can scale (stretch)
the picture on SD cable channels, since they don't fill the whole
screen. But on HD channels, the screen is locked into Full mode and
processes the signal in the correct resolution. This is using the HDMI
port on the TV (DVI - HDMI cable). Be sure you have an HD receiver
box.

Also another question... 3 questions in one here... I bought my TV and
there is an analog/digital button on the remote - you can switch
between the two signals. In digital mode the channels show up with
decimal points like "88.7" etc. What is going on here.. do I have
digitial cable or not ? This went away after the comcast guy
installed the comcast hd receiver box and set it up... I am wondering
what the hd box is using.. analog or digital.. ?

Thanks.

The box is using digital. Especially if it is an HD box (which I
assume it is from your previous question). The decimal points indicate
that you are viewing digital encoded signals (QAM most likely since it
is from the cable). You don't have these anymore because the cable
guy got rid of the coax coming into your TV and (hopefully) replaced
it with HD cables (DVI, HDMI, or Component). If you want to see these
channels again you would need a separate coax coming into you TV (i.e.
use a splitter and send one to the cable box like it is now, and the
other to the TV coax input), otherwise you have to use the box to
change (and tune) the channels. I should note that you will most
likely not get as many HD channels directly from the coax cable as you
will from the cable box. Premium HD channels are scrambled, and the
box decodes them correctly, the TV can't do this by itself.

So, 1)check to make sure you have HD cables from the cable box to the
TV (sounds like you do), and 2)check to make sure the cable box is
outputting to the correct resolution for you TV (may take a call to
comcast).

"asdf" wrote in message
ps.com...
Sony claims ( I'm going from memory ) that the static contrast of
their xbr2 is 1300:1 but with a dynamic contrast 7500:1..

What does this mean in actual use... if you compare a real 7500:1 tv
against the sony in different conditions ( dark room, medium room,
light room).. will the 7500:1 look better... or will the human eye
just not be able to tell because of pupil dilation from light level..

Sony dims the backlight in dark scenes where there are no bright areas, they
brighten the backlight when there are no dark areas... this is "dynamic
contrast". The display itself is capable of far less "static contrast"

On Mar 8, 10:10 am, "Doug" wrote:


It sounds like the TV is not scaling the picture, or you are not
watching HD content. Is your set a 16:9 ratio one? OR This could be
because the cable box is not sending the correct signal to your TV
(i.e. the TV needs 1080, but it gets 720, or 480 even). Not sure what
you mean by "...on a 1080 * 768 tv", Do you mean a different screen
ratio (widescreen vs. normal), or do you mean a higher/lower
resolution screen (1080p vs 720p).

Above fixed it .. the box was outputing in 480 mode. In this mode
when I switched to a highdef channel the picture would be a smaller
pic in the middle of the screen - now the picture fills the whole tv
on high def channels. On SD channels picture shows up but with two
bands on left and right of picture.


On my parents Sony HD tube (direct-view CRT), you can scale (stretch)
the picture on SD cable channels, since they don't fill the whole
screen. But on HD channels, the screen is locked into Full mode and
processes the signal in the correct resolution. This is using the HDMI
port on the TV (DVI - HDMI cable). Be sure you have an HD receiver
box.

If you scale the SD to HD things look stretched right.. faces don't
look proportional.. ?



The box is using digital. Especially if it is an HD box (which I
assume it is from your previous question). The decimal points indicate
that you are viewing digital encoded signals (QAM most likely since it
is from the cable). You don't have these anymore because the cable
guy got rid of the coax coming into your TV and (hopefully) replaced
it with HD cables (DVI, HDMI, or Component). If you want to see these
channels again you would need a separate coax coming into you TV (i.e.
use a splitter and send one to the cable box like it is now, and the
other to the TV coax input), otherwise you have to use the box to
change (and tune) the channels. I should note that you will most
likely not get as many HD channels directly from the coax cable as you
will from the cable box. Premium HD channels are scrambled, and the
box decodes them correctly, the TV can't do this by itself.

The cable guy put one cable going to the hd box and from back of
high def box looks like HD cable going to tv - going to tv is 5 cables
that look like they are stuck together and plug into back of tv into
something
that says HD input. I just have a regular dvd and that has 3 wires
plugging
into back of tv.


So, 1)check to make sure you have HD cables from the cable box to the
TV (sounds like you do), and 2)check to make sure the cable box is
outputting to the correct resolution for you TV (may take a call to
comcast).

Thanks. The abvoe worked great.

On Mar 8, 6:40 pm, "asdf" wrote:
On Mar 8, 10:10 am, "Doug" wrote:

On my parents Sony HD tube (direct-view CRT), you can scale (stretch)
the picture on SD cable channels, since they don't fill the whole
screen. But on HD channels, the screen is locked into Full mode and
processes the signal in the correct resolution. This is using the HDMI
port on the TV (DVI - HDMI cable). Be sure you have an HD receiver
box.

If you scale the SD to HD things look stretched right.. faces don't
look proportional.. ?


Just to clarify what I meant. If you watch an HD channel (CBS HD for
example), and they are showing SD content, then you can't zoom the
picture (which would stretch the faces), the display is locked to full
screen (with black bars on SD content).

Sounds like the cable installer used component video cables with audio
cables attached (5 total RCA plugs/cables). If you get audio (out of
your TV) from your DVD output right now, you probably have just the
composite video being fed into the TV. You could get better picture
quality using an S-video cable rather than the composite (yellow RCA),
or if you have a second component input on the TV, you could run
another set of component cables w/audio (5 cables again) to get the
best picture from the DVD (especially if you have a progressive scan
DVD player).