Rhworsham,
The only time that "insensible" enters this picture is the way I feel
after sorting out all the HDTV specifications. I want my NTSC!
Until there's a nice HDTV sale, that is.
To calculate the overall screen resolution -- the total number of
pixels -- of any TV set, you multiply the number of horizontal scan
lines by the number of pixels in each scan line.
For old times' sake, let's start with NTSC analog TV, the kind we've
all grown up with. Although NTSC has a total of 525 horizontal scan
lines, it only uses about 480 of these for the actual image. There are
720 pixels in each interlaced scan line, so our NTSC pixel calculation
looks like this:
480 scan lines x 720 pixels/line = 345,600 pixels
Rounding up slightly, we get about 350,000 total pixels on an
old-fashioned NTSC TV set.
The main promise of joy with digital HDTV (High Definition Television)
is its much greater resolution. HDTV pixels are smaller and squarer
than NTSC pixels, so HDTV can resolve finer details and hold smoother
curves. Plus, you get considerably more pixels to look at.
HDTV has a total of 1,125 scan lines, but it only uses 1,080 of these
for the actual image (hence the "1080i" HDTV specification). There are
1,920 pixels in each interlaced scan line, so our HDTV pixel
calculation looks like this:
1,080 scan lines x 1,920 pixels/line = 2,073,600 pixels
Rounded off, an HDTV set gives us about 2 million total pixels, about
six times the number of NTSC pixels.
Obviously, there's a lot more visual potential with HDTV, something
that also makes its movie-like 16 x 9 aspect ratio possible. NTSC only
gives a 4 x 3 aspect ratio, which ends up whacking off the ends of a
normal movie. You just can't see all those gladiators waiting in the
wings like you can with HDTV.
Sony's current HDTV models can be seen here:
Sony Style
HDTV & Widescreen (16:9)
http://www.sonystyle.com/home/scat.jsp?hierc=9685x9421&scatid=9421
Only one Sony HDTV model with a 32-36" diagonal, direct view CRT
(cathode ray tube) is shown:
Sony Style
34" FD TrinitonŽ WEGAŽ High Definition TV
KD-34XBR2
http://www.sonystyle.com/home/item.jsp?itemid=18111&hierc=9685x9421&catid=
While an actual pixel count is not given, the KD-34XBR2's top
interlaced resolution is 1080i, which means that it adheres to the
highest HDTV standard (with total pixels as calculated above).
One thing to remember about pixels: although a larger TV has a bigger
screen than a smaller TV, the total number of pixels on the screen
remains the same. There aren't more pixels on a bigger screen: the
pixels themselves are just bigger, so the actual resolution doesn't
change. If you get a big TV, you need to sit further away for it to
look as sharp as a smaller TV.
Now, let's look at the resolution of plasma TV screens, such as the
Sony KZ-42TS1:
Sony Style
42" Plasma WEGA™ Flat Panel Television
KZ-42TS1
http://www.sonystyle.com/home/item.jsp?itemid=29213&hierc=9685x9421&catid=
With plasma screens, you must consider their "native" or "addressable"
resolution. This is the maximum number of built-in pixels which they
can display. With the Sony KZ-42TS1, its maximum native resolution is
1,024 lines by 1,024 pixels. Let's do the math again:
1,024 lines x 1,024 pixels = 1,048,576 pixels
Thus, we get about 1 million pixels, half the number of total pixels
that HDTV is capable of delivering. Although the Sony KZ-42TS1 plasma
screen is an HDTV monitor, and will accept all HDTV signals (it is
"fully HDTV ready"), it simply cannot display all of the incoming HDTV
pixels.
Instead, the plasma screen "downconverts" the 2 million HDTV pixels so
they can be shown on its 1 million pixel display. The more lines a
plasma screen has, the higher quality HDTV picture it can display, but
it still may not be able to match HDTV's full potential.
While a plasma TV loses HDTV resolution (compared to a CRT), it may
not be a full 50% difference due to the particular conversion methods
used. Numbers and specifications can't completely determine overall
picture quality, so you should try to compare different TVs
side-by-side whenever possible.
Comparing the relative resolutions of interlaced video images to
progressively scanned images can be a little trickier. With
interlacing, the TV displays one half of a video image (its
even-numbered scan lines) first, then displays the other half of the
image (its odd-numbered scan lines). Your eyes and brain put these
alternately striped image halves together and you see them as a
single, whole image. This is the same "persistence of vision" effect
that theatrical films have depended upon for over a hundred years.
Strictly speaking, only half of an interlaced image is displayed by
the TV at any one moment. Using our current HDTV example of 2 million
pixels, the TV only offers 1 million pixels at a time.
Disregarding our persistence of vision, one could argue that only half
of the available pixels are shown, and thus claim that the TV only
delivers half of the potential resolution.
The highest progressive scan resolution from an HDTV set is 780 lines.
With 1,920 pixels per line, this gives us an approximate total of 1.5
million pixels. So, for a moment -- look *real* fast -- a progressive
scan display could theoretically offer more resolution than an
interlaced display.
However, that's not the way I, or you, or anyone else sees it.
Thank you,
Huntsman
References -
In particular, the glossaries and FAQs on the following Web sites were
very helpful.
Corporation for Public Broadcasting
Glossary: Digital TV Transition
http://stations.cpb.org/pdfs/system/0106_digitalkit/glossary.pdf
DigitalTV Zone
All About Digital TV
http://www.digitaltvzone.com/
DTV City
http://www.dtvcity.com/
HDTV Info Guide
http://www.hdtvinfoport.com/
Home Theater Magazine
http://www.hometheatermag.com/
PC DTV
http://www.pcdtv.org/
PBS
Digital TV: A Cringely Crash Course
http://www.pbs.org/opb/crashcourse/
Search Terms & Google Results -
1080i hdtv glossary
://www.google.com/search?sourceid=navclient&q=1080i+hdtv+glossary
plasma screen hdtv resolution
://www.google.com/search?sourceid=navclient&q=plasma+screen+hdtv+resolution
"persistence of vision"
://www.google.com/search?sourceid=navclient&q=%22persistence+of+vision%22 |
