Don't dump your CRT RPTV! - Page 13

Color shifting across the screen from CRTs has to do with the gun angle, not distance or anything like that. There is also a horizontal trapezoidal effect because the side guns must shoot at an angle, and this creates one side which uses slightly more phosphor than the other, resulting in a brighter side.

As an easy example, just take a flashlight and shine it perpendicular to a surface. Now shine it at a more extreme angle, say 45 degrees. Notice how the part on the near side doesn't really shine over that much larger an area, but the part on the far side is now shining over a much increased surface area? That makes that part of the beam on the surface dimmer because it is spread over an increased surface area.

The same basic principle is in effect with colorshifting, and lens striping is a way to cut back the light output on one side of the image to try to combat that, to maintain better uniformity.

I'm not sure why Glen characterized it as a square-image round-lens problem, as that really doesn't have anything to do with it. It does affect overall luminance uniformity, but not greyscale uniformity to red one one side and blue on the other.

Oh, I know. As soon as I get the thing off of the raised dias it's on now, I'm taking the board out and an EE friend will reflow the solder. It's just not been convenient to get in there, and it's only now that I have a new TV coming that I'm forced to move it anyway.

(I have a clip on the suspect connector, by the way, and that usually keeps the contact secure, but every couple of days I need to reach in and reposition it.)

Maybe so, but at some point, as the HDCP-encrypted pipeline gets longer and more strict, you may find you either cannot get certain signals TO your HTPC, or cannot get them out the back in unencrypted and/or analog form suitable for a TV without HDCP.


Only if the original material is 1080i. If the original material is 720p, as is the case with some broadcast material, then 1080i is a very poor second to 720p.

By the way, my Elite does not do 720p, period. 480i/p and 1080i, that's it.


Been using a (calibrated) CRT RPTV for 8 years, and as of last year, I am starting to have 4:3 burn-in, even though I rarely watch in 4:3 mode. I want to be able to watch 4:3 in 4:3 mode all the time, and that'd easily burn in visibly within six months.

A CRT display is beautiful once out of the box and calibrated, but it's just not going to last unless you always watch stretched and *never* have any static images on-screen. Even those annoying network logos can make a faint patch in the corner.

My comment was simplified in the respect that lens striping is done with a straight piece of material, installed at the edge of the lens, to reduce the reflected light. It is basically a custom configured lens hood. The less internal reflections inside the lens, the less the need for striping should be. Design has a large bearing on this.

That's kind of the way I was interpreting the statement, but striping the lens does not reduce lens reflections, but reduces light output by blocking active output in a localized area of the screen. Uniformity side-to-side with the off-center guns (R and B) doesn't have to do with lens spill at all. Having a superior lens has no bearing on the issue of this uniformity. This is why I am confused with your characterization of the issue.

Striping the lens does not deal with spill, rather it impacts light output in a localized way. I've never measured or heard any measurements with regards to striping on ANSI performance, but I would actually predict if it were a measurable change it would actually increase spill in the system and decrease ANSI performance compared with no striping. But light spill in the lens is not what striping is attempting to affect. It is not anything like a lens hood at all.

I'm not sure if you are confusing striping the lens with masking the tubeface perhaps? That would increase ANSI performance and reduce spill, but that would not have an affect on grayscale uniformity across the screen.

I guess I don't thoroughly understand the process. I haven't had time to do mine yet, when I get my new spectroradiometer, I plan to go there.

My take on this process is to reduce glare from the tube/lens, not cover the image. Striping the outer edge of the Red/Blue lens would essentially be hooding the lens to restrict light output to the image only. Am I wrong in thinking if the striping was to cover part of the image, you affect the projected image, like side blanking?

One thing I have noticed with my Mits is the Red and Blue tubes are not aimed at the center of the screen. Because of this, the image on the tube face is actually at the inner edge of the tube. This results in a large un used area of the tube from the image edge to the outer tube edge. Not good for stray light.

Here's some articles about lenstriping at Keohi HDTV.

Lenstriping

Advanced Lenstriping

Yes, indeed that's where the confusion lies. Because you're striping the exterior of the lens, you are not in (or really anywhere near) a focus plane. It seems illogical because you would at first assume that by striping the lens, that the active image would be totally obstructed, as would say blanking the image. You are actually applying the tape across the active portion of the image, however because you are not in a focus plane, it only blocks light output generally, not specifically.

For instance, if you were to apply tape to block light on the interior of the lens (which is a focus plane I believe) or on the tubeface itself, clearly you would then essentially "crop" off that part of the image. But on the outside face of the lens you're really far from any focus plane, so that blockage of light is non-specific. You can see this very easily by yourself by just taking one finger and putting it in the light path right in front of a lens (not touching the lens of course, but as close as practicable). You can see that you don't see a giant shadow of your finger on the screen where it is blocking light, but rather just a slight decrease in light output from that tube across a general area of the screen, because you're not in a focus plane. Try moving your finger around, and you'll see the general effect move to different parts of the screen accordingly, but again in a very generalized way. You won't actually be cropping anything from the image, even though you are blocking part of the light that is part of the *active* image. Now, if you use TOO much material to block TOO much light, such as your whole hand across a significant portion of the lens, you will actually start to lose part of the image, but notice how the edge of the shadow boundary is very large at the screen, and totally out of focus (you can't make any shadow puppets!), that's because you're not in a focus plane. If you went right up to the screen, then you could make shadow puppets (or if you had miniature hands and could somehow stick them BEHIND the lens at the tubeface!) because you would be very near/at a focus plane.

It's not the stray light that is being affected, but you are actually impeding light from the ACTIVE image from reaching the screen. It does seem counterintuitive because you look at a large piece of tape across part of the lens, and you'd think you'd have that part of the image cropped off, but that's not the case.

The pictures linked on the Keohi site illustrate this, and indeed some will stripe farther in on the lens, but leave some space at the edge of the lens, such that it actually crosses the lens (hard to explain) rather than just to come in on one side, while still remaining heavily towards one side of the lens. Okay, that last sentence sounds indecipherable, but it's late and I'm tired and I've been reading Hegel so my brain doesn't work! Maybe it will make more sense in the morning. Or maybe not!

As for the unused phosphor area, that's a different question, and that won't affect the grayscale uniformity (at least not really at all significantly), but one thing that can be done for that (on AC units) is to mask the tubeface. Guy Kuo described this once, it might be buried somewhere in the CRT forum archives, I don't see it on Keohi unfortunately. But basically he just used some black material and cut it out in the shape of the active-image trapezoid to block off all the unused phosphor. I don't know how significant an improvement this would be, I've never bothered to do this myself, but this would affect ANSI performance, and not have any impact on grayscale uniformity.

Hope that helps out!

Here is what happened..

1. You are a consumer and you hear that RPTV's produce the best picture right now.
2. So you research RPTV's and find out which is the best one to buy.
3. Then you read that you should get a calibration. So you call a ISF trained Calibrator and spend $400 on a calibration
4. The calibrator makes his adjustments, gives you your charts from the center of the screen and leaves.
5. You watch a movie and notice the outer edges of the screen are glowing red so bad that it is unejoyable.
6. You call the calibrator and say what up?
7. He says I don't know-maybe color uniformity-but I don't have experience in lens striping
8. So u need to put out more money for someone to lens stripe because not every calibrator knows how to lens stripe or doesn't include it in basic calibration.

So now the basic cutosmer is out money, because he did not know before hand what really needed to have done.
See my point? If you go out and buy a LCD or DLP projection you don't have as much to worry about, no?

No. There are compromises with any TV you buy. It is up to the individual to determine where he/she wants to compromise. There are so many issues, color decoding, DLP rainbow, microdisplay SSE, color gamut errors (some adjustable some not), geometry, screen door, posterizing, contouring, white field uniformity, and on and on. They all have issues, you just need to choose what sacrifices you want to make in image quality, and not all people choose the same ones. Then there are the physical differences, size, color, inputs, options....... No different from buying a car, everyone doesn't have a Porsche, Ferrari, Bugatti, .........

The need for lens striping doesn't suddenly appear with a calibration, it is just noticed after calibration because, you finally pay more attention to color uniformity and you have a reference to an accurate picture.

No.

You can't take one event and then generalize that ISF calibrations result in image problems. In case you're wondering, LCD & DLP sets require a full calibration before they look their best as well.

By the way, I did my own lens striping and it was relatively simple.

Once I set my grayscale I too noticed the color uniformity issue even more than before(probably because there was far less blue after calibration)...I quickly went in and lens striped and finally obtained a much, much better result. The problem is, the better result is of course achieved with the use of a color analyzer...and the cuts and drives were completely different with the lens striping. So I see Dlenart25's point....

I think all calibrators should mention this to their customers...

Thanks. I did not realize the other technologies had their share of problems as well-the only thing I knew about was less than spectacular blacks and the rainbow effect. As it turns out, I am finally happy with my picture. It has amazing depth, color unifomity, shadow detail, and PQ. It just took a lot of work?

PS. In case you interested in my full story you can check out this post:



So here's my last question: Does it make a difference whether or not you buy a HIGH end RPTV $3000+ vs a low end $1000 when a little bit of work will give you a great picture with a cheaper RPTV? I mean it appears you would have the same issues of color uniformity, calibration etc if you bought a High end?

I guess you cannot put Urls until you post Five times?

Test.

I sincerely apologize for that.

Here's my story:
http://www.hdtvoice.com/voice/showth...157#post161157

Definitely. All displays have weaknesses, personally I'm a CRTer and it's a technology that's hard to beat for my particular set of viewing preferences.

What is your opinion of SED technology?

Not seen SED yet.

Im willing to bet all or most of the people defending the CRT RPTV size as being ok , are staring at LCD monitors while theyre typing.

CRTs for PCs still have better color accuracy ,clarity and suffer nearly zero of the issues LCD monitors still have.

So if PQ is so important why arent you guys still on crt PC monitors ?



Listen if someone released an crt rptv that didnt have that dead space cabinet underneath id be with you 100%.
As far as im concerned neither side can win here. CRT's are truly outdated and whatever issues remain will remain so for as long as anyone can tell.
The other side has of course new technology ,aesthetics , and size on its side , but bum lamps , sse , green blobs and other things on top of the 2nd place PQ will keep it form being a true killer of CRT.

BUT at the very least current stuff has much more potential to improve , and if your making apurchase that you want to be around 5-10 years I cant imagine going for a CRT PTV. Just MO.

Um, well for folks that are dealing with video or critical imaging, they usually are.

Form factor and comfort viewing for things like internet browsing is not a critical task, so a lot of people prefer that.

The mistake you are assuming is that people place image quality above all else, which is both ignoring the fact that many people use displays for different kinds of imaging, and also that many people do not place image quality as paramount.

Totally agree.

When you spend 8+ hours a day on a computer screen, LCD is perfect for eliminating the fatigue that CRT can cause due to refresh rates. I prefer CRT for Graphics and CAD, but LCD for the basic computer usage is fine.

IMO, there are way too many people who don't have a clue what a accurate quality image looks like, or should look like.

And of course, you can also rest assured that practically all the content you are getting in the home was mastered using CRT monitors. As a CRTer I am susceptible to some amount of unavoidable bias, but regardless there are some legacies that CRTs (both good and bad) leave us with as a reference.

Wrong, mines a 21" Viewsonic CRT...

I'll worry about that when the day comes.
I expect to have replaced to TV long before it ever becomes an issue.


Actually, the PC does a very good job of scaling 720p to 1080p and outputting it as 1080i. I cant fault the end result, as it looks very good, and not noticeably different to display at 720p native.
It's a pain to change desktop resolutions for 720p content, and since 720p always looks soft compared to good 1080, I stick with 1080 for everything.



It would seem that you have the contrast set too high if you are suffering burn in.
My CRT RPTV's have been used as the only monitor on my HTPC, and have seen regular PC desktop use. I also watch plenty of 4:3 content unstretched.
Both sets where run in with full screen content, and have never been abused with high contrast setting. A screen saver has always been used on the PC.
My first CRT RPTV saw 4 years service used in that way, and my current one 2 years. I have no burn in problems what so ever, so it is possible to get a long and happy life out of a CRT RPTV if you are careful.
I cant imagine keeping a TV for 8 years, as technology moves to fast.

I expect to go with a 70 SXRD or 65 1080p Panasonic Plasma soon, if one or the other proves to be a match for my CRT RPTV.

I agree. It all depends on what you are going to be using the technology for. I watch my RPTV about 2-3 times a week. It is strictly used for Movie night with the Wife and Kids and High definition Sporting events such as Michigan Football and other High Def college football and to watch the Sucky Lions. It is not for everyday viewing. Now, that I have it calibrated and the color uniformity ironed out it makes movies look like I am at the theater! As a matter of fact it looks a lot better than my brother in laws 41 Sony LCD projection.

So when it comes to a PC its easy to understand why someone would choose an LCD over a CRT... Yet when the same reasoning is brought into the living room all of a sudden its difficult to understand why PQ isnt the pinnacle of importance ?

Not you in specific but to all those who jumped at my notion that the reason newer sets are so popular had much to do with the awful cabinet stylings and size of previous CRT rptv. Saying PQ is all that matters is ignorant and foolish.
LCD pc monitors , sattelite speakers , slimline phones , smaller pc cases.
If you can get the same end result from a smaller and better looking package most of the time people are going to jump at it.

Side by side its easy to see why a TV half the cabinet size yet the same screen size would appeal much more. How that sails over peoples head is beyond me.
Lugging a 65' crt rptv up or down a few flights of stairs is a mission , having to have it professionally calibrated is an added cost , having to rearrage components is a pain , and worrying about future compatibility is a nail in a coffin.

Got both. CRT for home gaming, LCD when I go to Lan Parties. When I watch movies CRT-RP.

Well, you are dealing with a certain degree of bias among users in this forum, especially some of the professionals who are extremely critical of image quality. The average television buyer is a far cry from the average forum participant, which is yet even still a far stretch from some of the folks who are extremely involved in video and so are even more critical.

I fully understand that people buy displays and don't actually really care that much about the image quality, but for extremely critical viewers who concern themselves primarily with the image alone, the rest be damned, there is certainly a disconnect between what the average person wants (form factor etc) and what a more demanding user wants (pure performance the whole way).

I would put myself largely in the latter category. It's why I have a 200lb behemoth displays. Where picture quality is of paramount importance, there are some sacrifices you have to make. Like back strains...

You are exactly the profile TV manufacturers are targeting. This whole issue to move from CRT to digital manufacturing is primarily a DOLLAR based decision, nothing more. The consumer electronics market is rapidly changing and there are significant dollars for manufacturers to go after. Something different like flat panels, creatd new demand, they're cool, gotta have one, who cares about picture quality, "look I have a xx" flat panel." The general consumer will buy millions of low performance displays, they are cheap! and getting cheaper daily. Don't even think that a major manufacturer would/will target quality over volume. They will make it as cheap as possible and sell you with advertising and questionable specifications that sound good. Some areas, military/air traffic control for one, still require CRT projection because of video quality.

Size is only one consideration of many in buying a TV. "Future Compatibility", who are you trying to kid, all TVs will remain backward compatible, but the future is evolving daily. Why even consider a 720p unit? What will be the optimal limit, 4-5 mega pixel?