Screenburn on a projector?

Discussion in 'Archived Threads 2001-2004' started by TylerL, Feb 16, 2002.

  1. TylerL

    TylerL Extra

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    Hello,

    One of the biggest worries for hi-def tv buyers seems to be the screen burn in.

    Does this happen with a projector? Obviously you won't be burning your wall or your pull down screen...but can you harm the bulb? Even if you do...shouldn't you just be able to replace the bulb?

    Or at worst..can't you just replace a part on the projector and have it like new?
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

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    Well, screen burn on RPTV isn't actual a burn on the screen, it's the tubes.

    The same problem exists for FP, but it depends on the type of projection. CRT FPTV systems use the same tubes used in most RPTVS, so the risk is identical.

    Some other Projector technologies are immune from tube burn (I'm pretty sure all DLP projectors are immune for example- I'm not sure about LCD or DILA-- it might vary on how the projection is actually achieved).

    -V
     
  3. TylerL

    TylerL Extra

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    I think Front Projecting is the word for what i was thinking of.

    Im thinking when you have a box that sits behind you and shines down the picture onto your wall or a roll-down (or other type) of screen.

    Rear-projectors are not intresting to me at all. I am more interested in Front Projecting because of the great size you can achieve.

    You say DLP is immune to screen burn? That is good to know. I am most intrested in DLP as aposed to other technologies.
     
  4. Vince Maskeeper

    Vince Maskeeper Producer

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    Yes, FPTV is Front Projection from a projector onto a wall/screen.

    Most Rear Projection sets us CRT tubes to achieve the picture- and these risk uneven wear from fixed images. Some Rear Projection sets actually use LCD as the projection source-- I'm not sure if those are immune to the uneven burn or not. Maybe someone else could chime in on that topic.

    I have a DLP front projector- and as far as I know, because there are no tubes, there is no risk up uneven wear.

     
  5. TylerL

    TylerL Extra

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    Well I'm not looking for pure size. More like 120 inches, that will be fine. Anything above that and I would think it would be more for a conference room or auditorium.

    What trade offs are there?

    I would be getting a projector that has both 4:3 and 16:9 native modes, and one that supports SD,ED, and HD tv.

    I might also hook a computer up to it too. Maybe.

    What are the draw backs?
     
  6. Vince Maskeeper

    Vince Maskeeper Producer

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  7. TylerL

    TylerL Extra

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    Well...that is alot to consider.

    I just said 120inches because that is 10 feet and i would think that is a somewhat standard size for FP's and screens.

    I have went to online FP vendors and look around at projectors like Proxima (these seem like computer specialized projectors) but i'm looking at projectors from a company called "in focus" that uses some Japanese technology for line doubling (i think...i only lightly skimmed it..). They look to cost around 5000-6000$...sounds fine to me.

    Now that i think about it...10 feet might be a little big...perhaps 7 feet would be more reasonable and a better solution considering brightness ,etc.

    As for all the scaling and stuff...for HDTV i was planning on using an HDTV tuner if that makes a difference. And for NTSC cable i was going to use a S-VHS deck and S-Video cable. Also a progressive scan DVD player.

    I have seen these projectors demoed and i like them...but i assumed it was set at 120 inches...but now that i think about it it was probably 80 inches which is fine for me.

    Hopefully it all works out and i find something that works.
     
  8. Vince Maskeeper

    Vince Maskeeper Producer

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    Tyler,
    I would suggest that you spend some time reading over at AVS:
    http://www.avsforum.com
    They have tons of info-- and for example if InFocus is available rebadged as a different brand cheaper, they would know.
    Remember if you go with a digital projector you should budget in a Scaler or HTPC to get the most out of it. And again, you will need some very high resolution (1280x1024 or so) to really do HDTV properly- so keep that in your mind when searching.
    -V
     
  9. Brian Dobbs

    Brian Dobbs Ambassador

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    Can front projectors still suffer burn in if all you play were anomorphic DVDs? Burn mainly occurs with the black bars right?
     
  10. Seth Paxton

    Seth Paxton Lead Actor

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    It's due to the temperture difference on the tube between hot and cold spots (light and dark). So it's not the black bars but rather no light in one area and consistant hotness (light) in another.

    As Vince said, CRT tubes, used in both SOME RPTVs and SOME FPTVs (3 different color tubes if you see a FPTV version) are the "famous" screen burn candidates. The only difference between Rear and Front is that rear uses mirrors to bounc the image up to the BACK of the screen while you watch from the front.

    People tend to think REAR means the projector that beams from behind you, but these are FRONT, meaning beams onto the FRONT SIDE of the screen, the side you look at.

    DLP bounces light of a grid of tiny mirrors, each mirror is a pixel. So far these arrays have shown no adverse affect to projection temps as far as I know and wouldn't be expected to have "burn in" as we know it anyway. The reason is because BRIGHT spots here just mean the mirror is angled to reflect more light, maybe the little deflection motor could get stuck in a position but those suckers are used in many industrial aps (non-television, biotech uses them for example) and the flipping life of the mirrors is heavily tested and very good.

    DLP is also being used in RPTVs now as well.

    D-ILA I don't know about for sure in terms of possible use damage. But I understand it to be something along the lines of DLP and LCD technologies.

    LCD bacially uses LCD just like in a calculator and BLOCKS the light by making some sections darker than others and I've never heard of a burn-in problem for that as it doesn't really make sense either. BRIGHT here just means the LC is not in one pixel as much. I suppose a pixel could end up on or off if the LC got gunked up, but again LCDs have a TON of testing thanks to decades of use before projector aps, so I wouldn't expect it.

    I have heard of LCOS (like an LCD version of DLP) having problems with images getting "stuck". In that case it's more like the LC shows a "memory" if an image is shown too long. The effect is that the LC doesn't come out "clean" after long usage on one image and you get a ghosting effect much like burn-in.

    If this has been solved yet or not I don't know, but it was a problem at one point. I'd be wary of that technology for awhile still.

    I think you will find that 105" tends to be one standard 16x9 screen size, there are several others. 10' is pretty big. I made my own 105" screen and sit about 15 feet away or so. Down to 10' away and that size starts to become a little too close and you can even start to see pixels.

    There are rules of thumb and formulas for seating distance to screen size that I don't have off the top of my head. Some research into the subject will ensure that you come across these rules of thumb.
     
  11. Vince Maskeeper

    Vince Maskeeper Producer

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  12. Bill Lucas

    Bill Lucas Supporting Actor

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    Just an FYI. Even if the entire screen is filled at all times when an RPTV is used the CRTs can still suffer from phosphor burn. It's the area of the CRT that is used that burns. RPTVs are no different from FPTVs in this respect. The entire face of the CRT is not used to project an image. Someone could be watching a badly burned RPTV and never know that it has phosphor burn. FPTV burn is easier to spot because if the image size is changed from a previous owner more or less of the face of the CRT will be used and phosphor burn is more easily spotted. Regards.
     
  13. Brian Dobbs

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    I'm kinda new to RPTV and Front Projectors so forgive me if my comments or questions are a little off. Let me rephrase/re-ask the question. I thought anomorphic dvds did not have the black bars, but they were created digitally to fill the screen of a TV. But since a projector isn't a TV, does it still do the same thing - digitally produce the black bars?

    If I'm still not getting it, could someone please explain how they watch movies with a front projector projecting the image onto a screen without getting the black bars?

    I'm looking for a surefire way of eliminating the risk of burn in. What are my options?
     
  14. Vince Maskeeper

    Vince Maskeeper Producer

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    1) Don't buy a tube based RPTV or FPTV, that would be a solution. Stick with a DLP or LCD type that don't have the problem.
    2) Understand that uneven tube burn won't happen in 2 hours-- rather we're usually talking hundreds of hours. If you keep your brightness and contrast levels at a resonable setting (if you aren't driving the piss out of your projector), then you should be fine for a while.
    3) Know what you plan to watch, and set up your screen/projector to support only that aspect ratio- and ignore all others.
    4) Use the entire tube face of your chosen projecor, and modify the aspect using actual optical lenses (this probably wouldn't work of a 3 gun CRT, so I wouldn't worry too much about it, since if you get a DLP which will work with lenses, then burn isn't an issue).
    5) Zoom/Crop all material to fit your screen, pan and scan style. This goes against pretty much everything home theater is about.
    -Vince
     
  15. Brian Dobbs

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    Hi there Vince. Thank you for posting such an informative response. I'm afraid I have been mistaken for someone who is new to Home Theater. I am aware of the idea of letterboxing and why there are the "black bars", but I just thought anomorphic DVDs did not include the bars, or unused space on the DVD itself. But what you're telling me is that they do include the bars? From my research on anomorphic DVDs, I thought anomorphic DVDs got rid of the black bars stored on the disc, and used the extra space to include added lines of resolution in the picture, and that the bars were added digitally by the DVD player to fill the unused space on the TV screen, 4:3 or 16:9.

    So, I'm still confused as to why a front projector would project the black bars or unused space onto the screen. I assumed that front projecting eliminated the process of a digitally derived black bar on the top and bottom of the picture. Is there more than one type of front projector? Maybe I'm confusing the issue. Isn't a front projector something that hangs from the ceiling and projects onto a screen, like in a movie theater?

    One more question....What is DLP?

    Please forgive me for not completely understanding.

    thanks
     
  16. Vince Maskeeper

    Vince Maskeeper Producer

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    There are 4 major types of front projectors: DLP, DILA, LCD, CRT. Each is simply a different type of projection method. DLP is digital light projection- which uses thousands of tiny mirrors that flip "on" and "off" to make the image.
    I would say research on AVS might help you:
    http://www.avsforum.com
    There are seperate areas for each projection type- and each has its own pros and cons.
    -V
     
  17. Brian Dobbs

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    thanks a million man! very helpful!
     
  18. Dylan Savage

    Dylan Savage Stunt Coordinator

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    How is burn-in on a RPTV any different from burn-in on a computer monitor? They both use CRT's, correct?
    Burn-in on any monitor made in the last 5-7 years is non-existant.. I leave monitors on and displaying the same thing for days at times.. and no burn-in. Why do RPTV's still burn? How severe is the problem? Can anyone tell me how long I could leave a RPTV displaying black bars for example before I should start worrying?
    Thanks guys! [​IMG]
     
  19. Kevin P

    Kevin P Screenwriter

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