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Discussion Starter · #1 ·
I know there has been a lot of discussion on the resolution capability of 7" CRTs for RPTVs not being able to display a full 1920x1080 picture. Is there anyway to actually know how much is being resolved on a 65" RPTV using 7" CRTs. I'm trying to compare in resolution terms to a 61" plasma display that has 1365x768. How much of a loss in resolution (if any) is there for the Plasma set compared to a 65" RPTV with 7" CRTs.


Thanks,


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Don't stress out about differences of a couple hundred lines of horizontal resolution. You won't be able to see this difference in real content really.


The good RPTVs are, roughly, getting about 1200 lines of horizontal resolution (that's all the way across the screen on a 16:9 set), when well calibrated. Some might get a little more and some a little less.


But all of these measurements are a kind of kludge, because there are lots of gotchas involved. Some sets will have better resolution in the middle than at the edges, for instance. And, the way you measure them is by using a pattern of alternating black and white lines. But interpreting that is a judgement call, because projectors are analog devices. if there is some overlap between the alternating lines (and there will be on all RPTVs showing a 1920 pattern), when do you quite counting them?



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There is this classic thread on resolution . I later asked LB about the Toshiba 56H80, and it came out one of the worst. In that discussion and also elsewhere, I heard that 1638 lines of horizontal resolution is the most one should expect for 1920x1080i, after filtering on the receiver side. The only RPTV's that are going to give that plasma display competition for HDTV are Philips sets. Although the Philips sets may be able to display more vertical lines horizontally than that plasma display, the plasma display will win big time on sharpness. That's plenty of resolution and I'm sure it would rock.



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Comparing CRTs to plasmas or other matrix-type displays gets into some interesting areas that aren't contrasted here too often. With matrix-element displays, supposedly, images are painted in a progressive format, typically in 1/60 sec, with each TV frame displayed all at once. With interlace displays on a 7-in. CRT, even lines are displayed in the first 1/60 sec (for NTSC), then odd lines are displayed in the next 1/60 sec. Our eyes blend the two images into one 1/30 sec TV frame. Seven-inch CRTs, of course, can display deinterlaced images, too.


But this gets complicated with one type of matrix display, the D-ILA, with three reflective-type LCD panels replacing three CRTs. JVC builds an unusual hybrid progressive/interlace system into its D-ILAs . (Mark Foster's technical explanation of this, at one time here , is missing with SEARCH, but perhaps is archived.) As I recall, for 1080i, pixels that wouldn't fit within the panel resolution limits in the first half of a frame are stored and displayed in the second half. This temporary storage of frame pixels applies for both horizontal pixels and lines, exposing your eyes to all the pixels present, even if that resolution exceeds the D-ILA panel matrix format.


With a CRT projector-type 1080i display, the electron beam in each tube creates 540 scan lines for each interlaced 1/60-sec field within each 1/30-sec TV frame. Video information is presented on these scan lines, but typically, with prerecorded moving images, this results not in horizontal and vertical resolution of 1920 X 1080, but more like ~1152 by 400 (to 800). (My 6/8 post here derives those numbers. And my 7/3 post here compares similar numbers, from ATSC committee tests, for both 720p and 1080i. Corrections, of course, are welcome.)


So, part of this great reduction in final resolution is brought about by signal filtering in interlaced HDTV receivers, part by limitations on most broadcasts, and part by how we see. What happens with a plasma panel is a good question. If 1080i is first deinterlaced, scaled to fit the panel's resolution, and displayed progressively, then our eyes don't see interlaced images. Would such progressive displays still require the ~20 percent filtering of horizontal resolution and significant vertical filtering of vertical information typical of CRT displays? Some A-B comparisons with test patterns--and moving video--would be interesting. -- John



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[This message has been edited by John Mason (edited 07-07-2001).]
 

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I would just correct Abdul's post on competition for plasma display, by saying most well calibrated 9" HD RPTVs, not just Phillips (Zenith, Phillips, Mitsubishi etc) should be able to compete nicely.
 

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IMHO, plasma is just another technology that's not ready for prime time. I also put cell phones (and my $200-300 a month bill) in the same category.


I've seen all the latest plasma products and they pale in comparison to a properly set up CRT fp/rp display. The "screen door" effect & black level are my two biggest complaints. The only place I would recommend a plasma screen for HDTV, is where space is the primary issue.


Resolution specs are just one small part of what determines how good an HDTV image looks. Other factors (like electronics bandwidth) cumulatively are a lot more important.


Anyway, if 2 million pixels is a full 1080x1920, I would guess most consumer 7" RPTV CRT's will product somewhere between 1 million at the very least & 1.75 million at the high end. Most sets probably fall in the middle somewhere, at 1.35-1.5 million pixels.


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[This message has been edited by Ken H (edited 07-07-2001).]
 

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Ken Ross, yes, sorry, I spoke sloppily. I meant 7 inch gun RPTV's as per the subject of the thread; many 9" gun RPTV's have very high resolutions.
 

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Discussion Starter · #8 ·
I guess the bottom line is to view each and compare visually.


Thanks for your responses!


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Regards,
Stevec>
 
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