DTV on standard 4:3 TVs and CRT damage
 

The laundromat in my town has a 23-25" Toshiba TV/VCR/DVD perched on top of a vending machine. I was there today doing my laundry, and noticed that the set was tuned to a football game; however, the picture did not fill the entire screen, due to the broadcast being in HD and this set being designed for the old NTSC 4:3 standard. This TV is left on from the time the laundromat opens until it closes--13 hours or so. My question is, will the CRT screen eventually be damaged from constantly showing an HD image with those black bars above and below the picture? I am also asking this for my own information, in case I have to replace my own flat screen with a CRT-based set. I have heard and read that it is indeed possible to burn the phosphors on the tube of an older CRT set by viewing HD images that do not fill the screen; in fact, I think I read here on VK of someone who had to junk an older set because of screen burn caused by extended viewing of HD content. Is this actually as much of a problem as it seems? :scratch2:

I would expect that given time it will leave a mark on the phosphors, not so much damage as it is normal wear, the black areas won't wear at all.

Does it really matter though if the set will never have to show a 4:3 picture again?

If you owned a CRT set and had a converter box you could alternate between 16:9 content and 4:3 content to even things out.

Do NOT get the idea that flat--panel sets are immune to burn. Even a LCD set can suffer "burn"--even though they have no phospor to burn. I HAVE seen this--and the effect is JUST like a normal phospor burn. It happened on an LCD set I accidently left a DVD on all night--and a logo got left in one place...it DID soften and go away--but at first it showed the "ghost" of that logo for some time. And I have heard that DLP chips can ALSO get "burned" in the same way--and get stuck--and show a ghost" of the bars...have NOT seen this myself though. In my experience-- DV tubes are MUCH harder to burn--than ANY other type of display..

I was referring to a CRT TV (not HD) with no cable box that is left on, showing a 4:3 image (with the black bars above and below, of course), some 13+ hours a day. Of course, the image would burn itself into the screen if it were stationary and left on the screen any length of time, but with moving images such as football games and other normal programming, I would think the chances of screen burn are quite slim. The TV networks would not leave their logos showing at the lower right or left corner of the screen if there was a chance said logos would burn themselves into that screen. I once asked a representative at Time Warner Cable (my area's cable provider) about this issue and was told that there is no danger of the logo burning itself onto the screen, since the TV picture itself is constantly moving even if the logo isn't.

VK member RCA2000 brings up a valid point regarding LCD screens. Yes, it is possible to burn an image into these screens if a stationary image is left on said screen any extended length of time (this is why the small "no signal" info box on most HDTVs is set to move around the screen after a very short period of time with no input signal); however, with normal programming where the images are moving, I don't think there is a problem.

DVD players also have screen savers that cause the manufacturer's logo to move around the screen if there is no video signal, again to prevent or at least minimize the possibility of a screen burn. My LG Blu-ray player has such a screen saver, and I am sure most other makes of Blu-ray and even standard DVD players have them as well. Imagine the public outcry that would result if these safeguards were not present in DVD/Blu-ray players and flat-screen HDTVs--most manufacturers would be facing lawsuits that could put them out of business in a hurry as soon as the complaints of burned screens started coming in. Most instances of screen burn in FP HDTVs are the result of leaving stationary images on the screen and forgetting about them, the same as the old CRT sets. The latter also had problems with ion burns which would damage the screen; however, once again, the main cause of screen burn with these sets was leaving stationary, bright images on the screens for extended periods of time.

Four-by-three TV programming, made long before HDTV, 4K, etc. were even thought of, is still shown on the retro TV networks (Antenna TV, RTV, MeTV) and even some independent broadcast channels, which often results in a picture with black bars above and below the image. With a flat screen this can be compensated for by the zoom function; just press the button on the remote or the set itself until the image fills your screen. However, with an older CRT set, of course, this is impossible. TVs built for the 4:3 NTSC broadcast standard do not have provisions for increasing the raster size; even Zenith sets with "Zoom" or older sets with a picture-size switch to expand the picture vertically cannot hide the black bars, and even fiddling with the height and linearity adjustments won't cause a 16:9 image to fill the screen, due to the nature of high-definition. Some stations show programs that are presented in 16:9 format that cannot be zoomed in on. I have seen this on the NBC affiliate here in northeastern Ohio; the picture will not fill the screen horizontally, and no amount of pressing the zoom button on my TV remote will bring in a full picture. These are regular TV programs, mind you, not commercials. I don't care what the TV programmers do with the commercials, but when I see a TV program that cannot be zoomed to the size of my screen, I wonder what they must have in mind.

My point was simply that if part of the CRT is not being used then the phosphors will eventually wear unevenly enough to be noticeable, but only if you start using the part of the screen that was not used before.
Most converters I've seen have option to change the aspect ratio to fit the screen though it doesn't always work.

While it's certainly possible I imagine it would take so long before the difference in wear between the black bars and the active screen area became visible that it isn't a practical concern for standard CRT sets. I've never seen it (though I've seen many other forms of screen burn).

I do see it often on old plasmas and used to see it on CRT rear projections sets before I stopped taking them.

As for not being able to zoom a program to full screen - This was often caused by channels broadcasting everything as 16:9 regardless of the actual aspect ratio the program is in. The well behaved channels would set the aspect ratio correctly on a program by program basis and by cable box and TV would adjust accordingly. In the end the well behaved channels were in the minority so I left everything on the 14:9 compromise setting when I got sick of messing with all the time. Now they're cropping some old 4:3 shows so they are full screen 16:9.

With regards to modern BPC sets who cares if there is burn in of any kind, in most places good ones can be had for free or next to nothing.

Stretching a 4x3 program horizontally is another sin the channels are guilty of, but what pisses me off most is stations that are hell bent on putting out ONLY a 16:9 frame despite showing some 4:3 content...What the cable co gets is a 'HD' pillar boxed 16:9 stream that they then letter box. The final result is a 4:3 image on a 4:3 screen that looks like it is under-scanned on all sides. :gigglemad: Effectively, and needlessly giving me a smaller screen size than the set I'm watching.

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^ That's a terrific idea, and surely implementable. The way it should have been when all broadcasts went digital.

That screen size would approximately simulate the pre-war 441i scanning standard. Showing the resolution that pre-war standard would have given us, but not in color. Maybe if TV stayed with 441i, the NTSC chroma subcarrier might have been right near 3MHz... Or that CBS sequential system might have become the color standard...

Some decoder boxes do have a "set by program" aspect ratio setting, so there are flags broadcast.

The TV will probably crap out before such marks will ever be noticeable..

I don't have personal experience with it, but a repair technician once told me that the result of prolonged display of the "black bars" on a CRT would be that those areas of the screen could end up being brighter than the rest of the screen, due to uneven wear/exercise of the phosphors. And, as others have said, it would take a very long time for it to begin to be perceptible.

So we have stepped forward AND backward with the implementation of HD....Brilliant!:no:

If there is still analog cable in jeffhs area like here. then there is still ways to balance out 4:3 and 16x9 screen wear to prevent long term wear....Time Warner Cable here still sends some commercials and I think some channel down the line in full screen4x3 NTSC. After x hours of letterbox play a few hours of 4x3 to balance out wear....Could even do this for a few hours after you sleep with a timer.

I don't think that you have to worry about letter-boxing or pillar-boxing on CRT sets giving uneven wear or burn-in symptoms. The set is still scanning the entire screen with a 4:3 image while it is operating - it's not like the areas with the black borders are not being used at all.

If you need to do something to make you more comfortable, then you can always connect a DVD player to the set and play a 4:3 DVD set to repeat all night once a week.

Eventually, a 4:3 CRT used for 16:9 programming constantly will likely show a burn-in problem, yes. The problem can be minimized and/or delayed by using the lowest acceptable contrast setting.

LCD panels do not get "burn-in" as far as I know, but they can get "image retention" as rca2000 mentioned seeing. That should be able to be fixed by using the display for moving images for just as long a time as the fixed image was displayed, more or less.

Aspect ratio switching can be handled automatically using the flags that already exist in the the standards - as long as the broadcasters use those flags correctly. Unfortunately most channels would set the flag to 16:9 for everything and either hard encode the black bars onto 4:3 programs or crop it to fit a 16:9 frame. In either case the only way to get what was originally a 4:3 program to display in full screen on a 4:3 TV is to manually mess with the settings - on a case by case basis.

On the (in the minority) channels that did use the flags correctly (both OTA and cable) the set top box would adjust on a program by program basis - sometimes it would even correctly adjust for commercials in a different aspect ratio to the program and correctly switch back when the program returned. 4:3 programs in full screen on a 4:3 TV - 16:9 programs either letterboxed or center cut depending on your setting.

The Pace cable box I had even supported the wide screen switching signals so it didn't have to resize anything to fit the chosen setting. It could display everything in it's native aspect ratio and just control the aspect ratio/zoom setting in the TV. I could unplug the 4:3 set, hot plug in a 16:9 set and without changing a single setting on the cable box everything would automatically display correctly.

Of course these features only work when programs are broadcast with the flags set correctly and 4:3 shows haven't been butchered to fit a 16:9 frame.

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As far as burnt phosphor is concerned, NOTHING I've seen can beat an original Ms. Pacman arcade cabinet I saw circa 2007 in a L.I. bowling alley..It was unplugged, and there was a perfect, distinct burnt-in image of the pacman home screen, with high-score and everything. It was amazing, like a photograph.

What is the mechanism for this rare, but long term "burn"... is there a small amount of UV light from the backlight that causes the dye in the color filters to fade in areas of long exposure? :scratch2:

jr

You could construct a fake prewar TV by getting a small CRT display (like one of those Chinese AM-FM-TV portable sets) and build a wooden cabinet (in the style of the day), set that set to really overscan horizontally and vertically so a B&W signal from a coupon eligible converter box (set to letterbox mode) shows visibly on the CRT around 441i line scanning. The overscan essentially throws away 84 lines, and the letterbox mode makes those thrown away lines black anyway. The horiz overscan would throw away the extreme left and right portions of the 16:9 image, so it would look reasonably geometrically correct on the CRT.

As for the audio, back before the war, the sound carrier was to be AM, not FM. So we'd need to degrade the sound quality a little, maybe add some video related buzz. Probably best approximated with a cap, to pass a little video signal above around 10KHz into the audio... :scratch2:

JR-

The problem with "burned-in" LCD images (whether or not it can be fixed; I have not yet had an opportunity to try) is supposedly that the liquid crystal elements or molecules get "lazy" or something roughly like that. So, with a given voltage they will no longer change polarity/position as much as they originally did. One of the "repair" theories I have heard is to run some kind of test video on such a damaged screen that would make the "lazy" elements or pixels eventually respond properly again.

Dr. Ido-

Like a number of other nice technologies used elsewhere in the world, aspect-ratio flagging has either never been used here in the USA, or no sets sold here have been designed to follow the flags, or both.

It does not help that sets such as Samsung LCDs can not even be made to remember the manually-chosen aspect-ratio settings on a per-channel (or specifically, per-subchannel) basis. One station here has a 480p or 480i subchannel (the equivalent of your 576p/i ones) showing 4:3 content but pillarboxed and coded as 16:9. My Samsung can remember aspect-ratio settings based only on the resolutions of various channels or subchannels. So, I either get that one subchannel double-pillarboxed (with everything on the screen super-thin) or, worse, I get all of the other 480p/i channels (which are all 4:3) stretched out wide and fat, filling the screen.

My Zenith DTV box does a decent job of interpreting aspect ratio flags and remembering settings, but I have cable so it is rarely used, and analog cable don't let me pick how they send it down the pipe (which can often be retarded particularly if the engineer at a given channel is dumb).

The Zenith DTT-900 and DTT-901 are among the tuners (built-in or external) that DO let you set and remember aspect-ratio settings on a per-channel/subchannel basis. Don't ever let go of it!

Interesting, Thanks!
Then I would guess that there might be some variation of this "ageing" phenomenon depending upon quality/purity/type of the LC material, cell construction, etc. Perhaps this is why it is rarely observed? :scratch2:

jr

I've seen videos of flashing test patterns that are supposed to fix lazy or stuck pixels if you run them long enough. I've also noticed that sometimes rubbing the panel in the affected area will get a stuck pixel to work temporarily, but I've only tried this with individual stuck pixels that were an inherent defect in that panel. I've never had a panel with "Aged" from image retention.

I thought that the aspect ratio flag was part of the MPEG2 spec - or does that only apply to DVDs?

I may be thinking more of the analog TV days, when other countries widely adopted 16:9 programming and had an aspect ratio flag in the signal. Yes, on some digital TV sets, I have seen an indication of the aspect ratio in addition to the resolution when the "Info" or "Display" or similar button is pressed, so you must be right about it being part of MPEG-2 video.