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I am wondering about the differences between 7" and 9" lenses on RPTVs (such as the 65" and 73" Mitsubishi's) compared to the differences between 7" and 9" lens front projectors. I have seen it said many times that the greater resolution of a source (? 1080p HDTV source, for example?) can only be appreciated on a front projector with 9" lens able to resolve this. The differences between 7", 8", and 9" in front projectors account for huge jumps in cost and I assume quality of image. Does this same quantum leap apply to RPTV as well, or is this a completely different situation. I have been told (on this forum) that the 73" Mits has a great picture, but specifically how important is a 9" lens on an RPTV??

Thank you,

Robert
 

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In your post above where you say "lens", you want to say "CRT". The lens is simply between the CRT and the screen, the diagonal size is actually the size of each of the 3 CRTS.


The jump in quality from 7" to 8" to 9" CRT isn't as big in RPTV as FPTV, for the simple reason that RPTV has a more complicated optical path - the CRTS are projecting off of mirrors and usually a lenticular screen on the way to your eyeball. These things tend to degrade the picture slightly relative to front projection.


Where you really want 9" is with the biggest screens, bigger than anything in an RPTV. That isn't to say you won't enjoy 9" RPTV, just that you might not be using the guns to their fullest potential, or, other video processing may sully the final result. Unlike resolution, one thing you can nearly always get from a bigger gun is more light output for a given image size.
 

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Quite a murky area, as you've noted, Robert. You might find some relevant material in this thread . Specifically, member LB's posts about actually measuring set performances with a colleague and a high-end pattern generator, plus my post referencing LB's year-2000 post, now dated, that compares measured horizontal resolutions and overall bandwidths. You have to take care, obviously, that you're comparing sets with roughly equivalent features, not 7-in vs. 9-in sets.


While the electromagnetic focusing of 7-in. and 8-in. FP sets could be expected to surpass the same-size CRTs with electrostatic focusing used for most RPTVs, I'd suspect there's a crossover point where a 9-in RPTV CRT could match or even exceed smaller FP performance. Of course, having equivalent wide-bandwidth electronics and a fine-pitch lenticular screen (~0.5 mm) is important for RPTVs, too.


With 2 years ownership of my 9-in.-CRT, 64-in. RPTV approaching this summer, I still haven't verified Philips claims of 'full' 1080i resolution. I often point out that even the best programs reach set displays at somewhat less than 1080iX1920 pixels, if you agree with what the experts that okayed the HDTV system assumed. As you may have discovered, magazine reviews of high-end gear are very vague on what they can actually deliver. Review descriptions often match 'golden-ear' reviews of audio gear in ambiguity. Add to that, advice to "just buy what looks good to you," overlooking that a store's programming source might be providing only, say, 1200 pixels of horizontal resolution, that that may be the practical limit of the set you're viewing, and that it can't display a good portion of, say, a 1800-pixel broadcast (after all filtering, etc.) from a live 1080i show.


Finally, suppose you could assume a certain equality of performance among 9-in. RPTVs. Lacking hard data, seems like the only way to really tell is LB's technique, using a high-end HDTV pattern generator on narrowed-down selections. A few other points to consider. Some early 9-in. models boost all signals, regardless of source, to 1080i, and many of the newest sets now boost resolution of 480i to higher levels. Not everyone is happy with this. Reviewers have pointed out that DVD test signals sometimes become too fuzzy to resolve at these boosted resolutions. Yet others point out, not too convincingly to me, that we don't watch test patterns and that video images on these boosted-resolution sets appear okay. Thanks, but I'd prefer both razor-sharp test patterns and motion video. On my 'ancient' 2000 Philips, a 480i test pattern is displayed at 480p, and the highest-detail Avia patterns appear stable and clear. -- John
 
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