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The extremely sharp text that I've seen displayed on DLP's always amazes me. Text displayed on RPTV's always seem blurred, but always razor sharp on DLPs.


I realize that the DLPs are for the most part ready to go "out of the box", whereas the RPTVs are usually at factory settings and require tweaking/calibration to obtain max pic quality. Does the sharp text quality translate to an overall sharper picture image for the DLP or can a RPTV be tweaked to obtain equal sharpness?


When viewing non-text images on both sets, the sharpness is not as evident, and the picture quality becomes closer between the 2 sets.


Sports and News programs have high amounts of text images, but most other viewing would not, and therefore the picture sharpness between the two sets becomes less apparent.


Yeah, that being said, I'd probably buy a DLP, BUT the cost factor is being balked at by the wife. For 1/2 the cost I could pick-up a nice Mitsu 42311.


Comments?
 

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Greetings


It can usually be fine tuned to be more razor sharp than what is out of the box.


Of course a CRT is also described as having a film like smoothness often lacking in a fixed panel digital display so go figure. :)


Regards
 

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Coyote Waits
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Here is a short list of RPTV types.


1. CRT

2. DLP

3. LCD

4. LCoS


They all probably benefit from tweaking or professional calibration. The CRT type sets just need it done on a more regular basis.
 

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CRT can be "smoother" be cause it do 1920 and 720 Horizontal info natively, and the pixel fill factor is >%100 percent.


While CRT can't resolve 1920, it does display it natively for "smooth" and even some detail that DLP can't show. For example let's say we have 960 lines lines across from a 1920 source, each 2 pixels wide. Like this:


xx xx xx xx xx ...

xx xx xx xx xx ...

xx xx xx xx xx ...

xx xx xx xx xx ...


Crt can resolve above, no big deal... But now think of DLP. it has 1280 pixels across, so it has to convert the above pattern into 1280. Not so smooth.


Now following is where CRT can actually display more detail than DLP, even though it is not as "sharp." Take same pattern, and shift each line 1 pixel.

(I had to edit it, it was being reformatted after posting, I think you get idea)

0xx xx xx xx xx...

1 xx xx xx xx xx ...

11 xx xx xx xx xx ...

111 xx xx xx xx xx ...



While the crt can't resolve individual pixels above, it will start to turn on/turn off the beam at the appropriate spot, which is on an individual 1920 pixel boundary. On this pattern, the DLP will again have to some how figure out how to fit the pattern into 1280 pixels. As above, there will be conversion artifacts on DLP. Not major, but they're there. (Not smooth.)




Now I personally crave that sharp edge on text. As Michael TLV suggests, you can improve CRT focus. Both the optical lens, and the electrical/magnetic lens that the crt beam goes through itself. I spend hours adjusting astigmatism magnets so the beam will go right thought the sweet spot of the focus grids. Hours because it can have an effect on centering magnets, so entire convergence has to be redone.


After all that work, real sharpness is improved on CRT, but still not "razor sharp" like DLP is right out of box. DLP is not for me (yet). But, if the conversion artifacts mentioned above don't bother you, and blacks are acceptable, DLP has a fantastic picture, without the bloody headaches.


Note that DLP will display 720p stuff natively. Most crt's will have to convert this to either 480p or 1080i. However, the eye is not as sensitive to vertical artifacts. I have put in a 1280 x 720 test pattern into my latest CRT, and it does so well I at first wondered if it was doing 720p natively. I don't think it is, but the shifted pattern above came out very good. Could just be that CRT "smoothness" ;)


Good luck with decision. (PQ aside, don't forget no screen burn issues with DLP)
 

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Coyote Waits
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Quote:
Originally posted by David Mathews
Note that DLP will display 720p stuff natively. Most crt's will have to convert this to either 480p or 1080i.
Outstanding reply! May I add one "extra" point.


Of the DLP sets available in the market Samsung takes advantage of the native 720p capability of the DLP chip by passing a 720p signal straight through for display without any conversion.


RCA passes all external signals, including 720p, through an analog stage before re-converting them to 720p for display. It also looks like the RCA sets will not except 720p through component or DVI inputs.


All manufacturers do not use the DLP chip in the same way. :rolleyes:
 

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Quote:
Originally posted by greg3278
DLP's have no convergence so they should always be more capable of a sharper image than even a properly converged RPTV(CRT).
Yep, for HTPC go DLP, LCD, or LCOS...much better options than CDRT.
 

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Quote:
RCA passes all external signals, including 720p, through an analog stage before re-converting them to 720p for display. It also looks like the RCA sets will not except 720p through component or DVI inputs.
Say it isn't so! The one point where you can really make a DLP shine, and they cripple it???


The possibility of using an offboard scaler back into DLP set ALMOST made me pry my fingers from my CRT. If your comment is true, I'm darned glad I didn't answer that RCA ad for HDTV engineers a few years back! LOL.
 

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Quote:
Originally posted by greg3278
DLP's have no convergence so they should always be more capable of a sharper image than even a properly converged RPTV(CRT).
Careful, while on the surface true, its not really in practice.


Some CRT sets (but not all) have very good service mode level convergence. You can indeed get it spot on. You do have to maintain it, which is a real pain, but you can get convergence spot on.


An example why its not the convergence. Todays 7 inch guns just don't focus the beam. Its kind of a spot with a Gaussian distribution. Kind of bright in center with a dim halo around it. It is this halo that makes CRT "fuzzy" compared to digital sets. Even if you turned off two of the three guns, and just had red on for example, you would have a slight red halo around spot.


Service level convergence control is good enough on some sets you can have a one pixel wide spot, and line all three spots right on perfectly, but halo is still there.


As I said in above post, you can minimize it, but not eliminate it.


Now here's where it really gets confusing. Its not CRT technology that really makes it fuzzy, its the current implementation of CRT that makes it fuzzy.


Since the set will scan 480p and 1080i, they size the beam so the scan lines almost touch in 480p mode, and are really getting close to touching in 540p mode. If they didn't, the scan lines would be objectionable even to non-avs folks. (hey honey, what are those black lines all over screen!???) Thus, the beam, and the surrounding halo, is currently somewhat intentionally large so the scan lines won't show up.


If/when they start moving CRT sets to scan 720p natively, they can scale 480p to 720p. They can then reduce beam/spot size without getting annoying black lines between the scan lines. The smaller beam spot will also reduce size of halo, which will reduce fuzziness. Then, take the next step to 1080p scanning and you can reduce beam even more. However, now you probably need nine inch guns. (Mitsubishi is starting to put 9 inch guns on larger sets, with volume, price may come down.)


Back to your convergence point. Even if we get better scan modes/beamsize, convergence is still needed. While todays sets can do it right, is still a pain. Both for user, service personnel, and factory. Thats a strong incentive for further development of digital.
 

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Quote:
Originally posted by PaulGo
David, its a good thing you are not working for RCA since the are laying off over 1100 of their US staff and are looking for a Chinese partner.
Wow, double glad now. Of course sorry to hear that. Not good to hear anyone laid off.
 
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