[opendtv] Re: The Math on Screen sizes
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 07 Jun 2004 20:27:35 -0400
It probably seems larger to me because, as I stated, I was comparing
it to my memories of computer displays. For instance see the "How
Stuff Works" page, at http://computer.howstuffworks.com/question401.htm
where it says:
--------
In computer displays, common dot pitches are .31mm, .28mm, .27mm,
.26mm, and .25mm. Traditional televisions often use a larger dot
pitch, about .51 mm, and large screen TVs or projection devices can go
up to 1 millimeter in pitch.
--------
I don't know if they are the experts. I just Googled on dot pitch and
that's what came up.
And I'm sorry if you are still put out by my comments on the
broadcasters, but I believed what I said. Let's move on.
- Tom
John Willkie wrote:
> Hmmh.. were those old computer displays monochrome (one dot per pixel) or
> color (three dots per color)? When you mention dot pitch, were you talking
> about pixel pitch or dot pitch?
>
> Notice how I don't do unsupported conclusions, but that's all you have (just
> like your unproven and unprovable conclusion that broadcasters are holding
> up the transition).
>
> You talk about dot pitch (you apparently meant pixel pitch) seeming quite
> large. Could you provide examples?
>
> John Willkie
>
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Tom Barry
> Sent: Friday, June 04, 2004 8:05 PM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: The Math on Screen sizes
>
>
> John Willkie wrote:
> > B-U-L-L-S-H-I-T.
> >
> ... and ...
> > Get real.
>
> John -
>
> I assume from your invective that you disagreed with something I said.
>
> IIRC there are 25.4 mm per inch, so at a .7 mm dot pitch (which seems
> large) there would be 36.28 pixels / inch, or 1814 pixels on a 50"
> wide screen. I remember some of my computer displays of old had dot
> pitches in the range of .28 or so some time ago. I assume they would
> be much better now. And of course my 55" Toshiba RPTV does not have a
> grill or shadow mask and there is no sense in trying to measure it
> like some camera folks do saying it takes 3 pixels of 3 colors to make
> one pixel, since they overlap anyway.
>
> And yes, no surprise, I still believe HDTV displays have much more
> resolution than NTSC TV sets. Duh!
>
> - Tom
> John Willkie wrote:
>
>>B-U-L-L-S-H-I-T.
>>
>>1080 pixels across, using 0.7 mm dot pitch, requires a screen 89.29 inches
>>across, with a 4:3 set having a diagonal measure of 111 inches, or a 16:9
>>screen of 102 inches. How many 9 FOOT screens have you seen?
>>
>>And, 1080 pixels renders only 540 "lines" as that term has been used in
>
> the
>
>>TV business since BEFORE 1939.
>>
>
>
>
>>Get real.
>>
>>John Willkie
>>
>>-----Original Message-----
>>From: opendtv-bounce@xxxxxxxxxxxxx
>>[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Tom Barry
>>Sent: Friday, June 04, 2004 4:28 PM
>>To: opendtv@xxxxxxxxxxxxx
>>Subject: [opendtv] Re: The Math on Screen sizes
>>
>>
>>Most CRT based HDTV displays are capable of displaying 1080 lines, in
>>an interlaced fashion, though if you want the proper 16:9 aspect ratio
>>on a 4:3 HDTV display the CEA has decided it can still officially be
>>called an HDTV set if it displays a 16:9 area using only 810 of the
>>1080 lines. However most newer CRT based 4:3 HD displays can instead
>>use a squeeze function to place all 1080 lines in a 16:9 area if desired.
>>
>>An NTSC analog TV only displays about 480, interlaced.
>>
>>And as already discussed there are nuances of effective resolution,
>>grill aperture, and spot beam size which detract for the stated numbers.
>>
>>But any HD display still displays a LOT more resolution than an NTSC
>>480i display.
>>
>>- Tom
>>
>>John Willkie wrote:
>>
>>
>>>So, ONCE AGAIN, what EXACTLY is the difference between the screen
>>
>>resolution
>>
>>
>>>of an NTSC set (440 lines?) and an 4:3 "HDTV" set capable of 810 lines?
>>>
>>>John Willkie
>>>
>>>P.S. Don't think for one second that I didn't notice you offering that
>>
>>one
>>
>>
>>>of those 4:3 sets was "HDTV" and now you are saying that somebody else
>>
>>said
>>
>>
>>>it. Me, I'm responsible for my words. Even erroroneous and bad ones.
>>>
>>>-----Original Message-----
>>>From: opendtv-bounce@xxxxxxxxxxxxx
>>>[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Craig Birkmaier
>>>Sent: Friday, June 04, 2004 5:40 AM
>>>To: opendtv@xxxxxxxxxxxxx
>>>Subject: [opendtv] Re: The Math on Screen sizes
>>>
>>>
>>>At 6:25 PM -0700 6/3/04, John Willkie wrote:
>>>
>>>
>>>
>>>>Please, please, somebody show me where I have gone wrong.
>>>
>>>
>>>Nobody ever said anything about 810 samples per line being HD,
>>>although most HD capable display cannot resolve much more horizontal
>>>detail.
>>>
>>>The 810 number comes from the CEA. It is a caveat for 4:3 CRT based
>>>RPTVs and relates to the number of active lines of video when a 4:3
>>>HD capable display is showing 16:9 source. In essence, the display
>>>scans 1080 lines (two 540 line fields, spreading the lines over the
>>>entire vertical area of the 4:3 display. The alternative would be to
>>>reduce the vertical drive and scan only the 16:9 portion of the
>>>screen with the full 1080 lines; but many manufacturers experienced
>>>differential burn in using this technique. The CEA agreed to allow
>>>manufacturers to stretch the 1080 lines over the 4:3 screen, Using
>>>only the central 810 lines to display 16:9 HD source. The remaining
>>>lines are typically filled with grey to average out burn-in, although
>>>some manufacturers do allow the unused area to be black.
>>>
>>>As for the actual horizontal resolution of CRT based displays, there
>>>are two different issues.
>>>
>>>For direct view CRT displays the limiting horizontal resolution is
>>>determined by the shadow mask of the CRT; the number of slits or dot
>>>triads across the width of the screen; The best I have seen in and
>>>consumer HD display of this type is about 850 samples per screen
>>>width. I think that Princeton offered a 720P display with better
>>>horizontal resolution. You don't need a spreadsheet to figure this
>>>out...just count the slits (or look in the specs for the display).
>>>
>>>For rear projection CRT displays the situation is very different, as
>>>the tubes used for these sets do not have shadow masks. Thus the
>>>limiting horizontal resolution is determined by the spot size of the
>>>beam and the band pass of the amps that are driving the CRTs. Again,
>>>looking at the specs, you will find that most CRT based RPTVs offer
>>>no more than 850 lines horizontal resolution.
>>>
>>>Regards
>>>Craig
>
>
>
>
> ----------------------------------------------------------------------
> You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
> - Using the UNSUBSCRIBE command in your user configuration settings at
> FreeLists.org
>
> - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
> unsubscribe in the subject line.
>
>
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
