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9FT screen....Some figures....

Discussion in 'Projectors, Screens & Video Processors' started by Gordon @ Convergent AV, Jun 15, 2001.

  1. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    There's a bit of a debate going on at the HCC feedback forum about an install in last months magazine. It brought up an interesting thing....

    I'm not going to comment too much but here are a few figures to digest. They are ft Lamberts measurements for the reflected light on some Stewart Screens with different projectors. Two screen materials are quoted one a 1.8gain and the other 1.3(studiotek130) they are both for Microperf versions (ie teabag holed ones which reach THX spec)

    Now, 9FT is big. I've done a 9ft screen with a Seleco500. The customer is happy. So am I. It was with a normal Studiotek 130, no perfs, in a room which can be completely blacked out. Ideally you're looking for over 8 nearer 10 in a blackout room.

    Anyway here they are for discussion..What would you do?


    SonyD50HT Ultramatte200 4.8ftLbrts
    Studiotek130 3.47ftLbrts

    Seleco800HD Ultramatte200 5.7ftLbrts
    Studiotek130 4.12ftLbrts

    Sony G90 Ultramatte200 10.5ftLbrts
    Studiotek130 7.58ftLbrts

    Sony VPL10HT Ultramatte200 29.99ftLbrts
    Studiotek130 21.66ftLbrts

    These figures were calculated using Stewarts "ScreenAssistant" software.

    Gordon
     
  2. Jeff

    Jeff
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    :confused: in Basingstoke. Some CRTs not bright enough for large screens?

    Jeff

    [ 15-06-2001: Message edited by: Jeff ]
     
  3. Jeff

    Jeff
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    Gordon,

    Based on what you have just said in your post, if someone wanted a home cinema with a 9ft screen I would recommend a G90 and a Ultramatte200 screen. How much ?

    Jeff
     
  4. Nic Rhodes

    Nic Rhodes
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    Interesting stuff. I am trying to work out what is the largest size you could project from an NEC 9PG. I read somewhere Joe Kane recommends no more than 7 foot. What do people think / use themselves?
     
  5. uncle eric

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    Gordon,
    Thanks for the figures.

    Jeff,
    Basicly the above is what I've been saying post after post in the aforementioned thread. Gordon is a professional installer, so are Dawsons. What gives! There are many other aspects of their install that perhaps should have been pointed out as questionable. This Jeff, was my whole point!!!

    Eric
     
  6. uncle eric

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    Nic,
    Many reviewers and videophiles Joe Kane and John Gannon included use around 100" diag (around 7ft wide), some even smaller, as reference when using front projection.

    Apparently, Joe Kane does most of his viewing on a 29" Princeton Graphics monitor through a 30 grand S&Wilcox processor. I know what you are thinking. Mad Genius :eek:

    Also, I asked Don Stewart (Stewart Filmscreen corporation) what were the average screen size's that people used both here in Europe and the USA. Some interesting reading will probably follow. Here is the thread www.avsforum.com/ubb/Forum9/HTML/001080.html


    best wishes
    Eric
     
  7. GarryF

    GarryF
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    Nic,

    As Gordon says I have a 80" 16-9 screen, scaler is a quadscan. I usually sit about 3.5 metres away and find any closer and you spend most of your time looking at the poor image quality (in general) The exception to this is on a HCPC where I can pull the sofa forward quite a bit and still get a film like experience.

    Another thing to consider is I often watch the projector with curtains open and just now in the summer still get an acceptable picture for most stuff, I expect with a bigger screen this wouldn't be possible.

    So I guess you should figure out how far you will be sitting from the screen, too close with a screen that's too big and it'll be like watching a blown up JPG with most sources.
     
  8. Jeff

    Jeff
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    Eric,

    OK you do have a point, but it's quite possible that they went for the large screen now with the knowledge that they would be replacing the projector in the not too distant future.

    Jeff
     
  9. uncle eric

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    Jeff,
    Your point is very valid. Lets hope new tech projectors can catch up with CRT soon. I dont like the way my Barco is positioned right over my head. Did I hang it right? ouch :(

    Eric
     
  10. Jeff

    Jeff
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    That reminds me of the Philips plasma ad. You wouldn't catch me lying in bed under one of those things. I wonder if the happy couple got paid danger money. :D
     
  11. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Eric,

    I'm not getting involved in what is right or wrong here. :rolleyes: I don't know the facts. All I'm doing is giving some info for folk to better understand the sides of each argument.

    Nic,

    45" X 80" or smaller would be good. GarryF on this site has such a screen, one of the other guys who got a NEC9 has a screen of this size. I worked out a rough figure based on a Runco930 chassis. You'd get around 10ft lbrts at that size, with a 1.3 gain screen.

    Gordon
     
  12. Roland @ B4

    Roland @ B4
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    All this specmanship dives me bonkers.

    From ths figures the 9" G90 hastwice as light output as a 7" D50 which is fooey. it may have nearly twice the phosper area but the beam current limiting will prevent it being double.

    At the end of the day is it an acceptable picture for the room conditions and the viewer?

    12/14ft lamberts is the figure that most cinema screens try to achieve from an open gate film projector (no film). this level has been found the most acceptable for correct black levels (the only way cinemas can control contast)

    Whilst a CRT projector can achive this (10-14ftlamberts) mystical figure for a 10% peak white box it is not the ideal way to say that a projector has the correct properties.

    Consider this, we can read a newspaper in sunlight but also in a darkened room by candle light. Our eyes adjust. :
     
  13. squid

    squid
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    personaly i only see one real reson for having such a large screen and that is show off value "look at the size of mine "

    i have a 61/2 feet wide screen and i find it more than anough to get the effect of a cinema

    how far is it realy practical to push a pal signal even with the best of video processing.

    personaly i would prefer a smaller screen and to sit closser . after all it is relative . as far as are eyes are concerned siting close to a small screen is just the same as sitting a mile away from a masive screen

    the factor with screen size is the amount of people watching it. in most situations it will just be us and maybe a few mates so such a large screen is not needed

    i supose though the main deciding factor is personal tast. if you want one get one. just like the turner cinema . i supose if they are happy with the lack of quality and brightness then that is up to them in the end

    i would have just like to have seen the thought behind the use of such a large sreen in the mag. i would hate to see someone pick up the mag and think that such a larg screen is a good idear in there situation when it may not . not everyone has the benefit of the forums and may make decissions soley on what they have seen in hcc (i have in the past)
     
  14. ReTrO

    ReTrO
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    Anyone here used a Barco G5 R6 DLP projector with a Snell and Wilcox Interpolator Gold? Or either?

    I am looking for something to 'rival' 35mm film here, and I know even this combo won't be the same as 35mm!

    Any other recommendations are welcome. Barco CineMax was considered but is too big!
    Other scalers etc?

    Cheers guys!

    Rick

    PS It's not for me! I'm not that rich!

    [ 17-06-2001: Message edited by: ReTrO ]
     
  15. Roland @ B4

    Roland @ B4
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    R6 is not launched yetso don't know
    Contast ratio even on an SLM G5 is 400:1

    SLM G5 (1024x768 5000 ansi lumens)
    SLM R6 (1280x1024 6000 ansi lumens)

    (film can reach 4000:1) most about 1000-2000:1

    S&W Interpolator will definitly improve the image but the internal pixel map processor from Barco is pretty good.

    I defy anyone to beat interpolator + Cine Max. unless it IS film.

    As regards veiwing distance even THE article proves this. ideal postion is right under the CRT projector. IE 1.5 to 1.7 times the screen width.

    However I'm currenty watching TV from 17 times screen width.
     
  16. Jeff

    Jeff
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    Gordon,

    Do the figures you quoted apply to 9ft screen with a 4:3 ratio? What happens if the screen is 16:9 or 2.35:1?

    Cheers,

    Jeff
     
  17. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The figures were for 9ft width and 16:9 aspect ratio. I'll check any diff for other aspect ratio's tomorrow if I've time. It's a bit late tonight and I'm knackered after working all weekend.....

    Gordon
     
  18. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Hey B4: I was playing Devils Advocate or didn't you notice.....

    The idea was to see if anyone would suggest using a VPL10HT instead of a CRT. Yes it would be brighter but would it be a better image? I doubt it.

    Ultimately though you have to get enough light on the screen to illuminate it. In a completely darkened room you can get away with quite alot. The D50 in the install in question probably looks fine. It would look better on a smaller screen and better still if it weren't micro-perf.

    There are other projectors for similar amounts that may have been more suitable but if the installer is good with Sony's then that's the way to go. I would still advocate trying to achieve around 8ft lamberts anyway.

    The idea, as you say, is always to make sure the customer is happy. That doesn't preclude explaining possible benefits of doing it other ways though I'd hope you agree.

    Gordon
     
  19. Roland @ B4

    Roland @ B4
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    Gordon
    The figures quoted seem to work on the ANSI lumen out put. Which measures a well setup projector on a full white field. something CRT projectors don't do well because their beam current is limited.And something that is very rarley used in films.

    The avarage movie scene has about 10 to 15% pure white. which your LCD and CRT should produce about 1000 lumens. Its only when you move into really bright whole scenes that the figures will start to sepearate.

    I don't contest the ANSI measurements or their way of doing the tests. I question its relevance in home Cinema.

    Gordon 8ft lamberts measured how?

    The calculation I have seen used is.
    Proj output (ANSI) divided by screen surface in square feet multiplied by the screen gain give you the foot lambert figure.

    D50 = (200? ansi)
    9ft x 5ft screen = 45
    screen 1.3 gain

    200/45 x 1.3 = 5.7

    specmanship wins again

    Any one got a light meter and we'll measure a frame.
     
  20. Roland @ B4

    Roland @ B4
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    Gordon
    If it was that easy we wouldn't be doing this.

    If it down to me then peak lumens would be the figure to use rather than ANSI lumens

    As a general rule to people who know how the different projectors work, the figures give an indication.

    But its a bit like comparing performance of petrol cars with diesel they are not designed to compete in the same areas.Each has its merits but in differing areas. same with LCD and CRT.

    Projector manufactures have competed in the light output specs for so many years some of them have lost the plot and we have been sucked in too.
     
  21. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I was told a story recently which may be the equivalent of a HomeCinema "old wives tale".

    I asked someone how on earth some manufacturers of certain products managed to claim the mad light output and contrast figures they did when it was obvious on seeing said items that they were taking "poetic licence" to extremes.

    The answer was that there are some who measure ALL ON/ ALL OFF contrast by attaching a light meter to the front of the lens and BLASTING it at maximum light output. That's the "full on" reading. Then to get "full off" you take the thing out the room and measure how dark it is!

    Do you think this sort of thing might actually happen? :eek: It's quite funny though, and would explain alot.

    I do get sucked in sometimes. Coming from the hi-fi industry I should be used to the "watts" counters, just like Lumens counters.....Only the lumens counters are brighter :D "boom boom"

    Gordon

    [ 18-06-2001: Message edited by: Gordon, StereoStereo ]
     
  22. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    B4 don't disagree with you. The human eye has a much better ability to compensate for darkness than brightness. CRT's as we both know are not good at full white fields but are good at small white fields...

    These two things mean that light output specs for CRT's v Fixed Panels don't tell the full story.

    Here's a thing though. If we can't use the generally accepted method you outlined above and Stewart use for specing screens, what method do you suggest. It's an expensive mistake to order a 12ft wide screen only to find it's so dim on your 7" CRT that after a years use you regret it. Is there an alternative method. This is not a critisicm. You have raised a valid point and one I'd like to get to the bottom of.

    Gordon

    I'm looking in to the possibility of getting two identical projectors set up on screens of 6ft and 10ft at the event. Not sure if I'll manage it though. Running out of room.....
     
  23. uncle eric

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    Gordon,
    Of course the other thing to remember is that new CRT's lose a fair percentage of their brightness well before (in most case's) 1000 hours or so.
    Yet more problems for big screen, small crt installs. Hopefully the Turners wont notice too much??? As you say, eyes adapt.

    Eric
     
  24. Roland @ B4

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    What sort of percentage loss do you think you would expect at 1000 hrs
     
  25. squid

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    i would like to know the answer to that

    what percentage is lost after a certain tube life 1000h, 2000h , ect ?

    this would be an interesting thing to know. i have heard that the light output go's down is it realy such a big problem (i would have thought it could be a problem if you do go to these biger screen sizes)

    has this been mesures through the full life of a projectors tubes? :confused:
     
  26. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    I have no figures to back up the following statement but it might help.

    From what I understand the following holds true. The tube of a crt projector can be classed as worn out when it's light output ishalf what itstarted at. So that's 50% over 7-10,000hrs. NowI don't know if this is fact and I don't know if thereis a slowing drop off of light output.

    I do know that I've got a client with a Seleco500 on a 9ft screen and it's probably up there at 2500-3000hrs I'd guess. Last went round there with an FMJ27 dvd and it looked plenty bright enough to me. Pitch black room though.

    Perhaps Chris or Alan from Owl could comment on this one unless B4 has the answer to his question.

    Gordon

    [ 20-06-2001: Message edited by: Gordon, StereoStereo ]
     
  27. Roland @ B4

    Roland @ B4
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    He who has the highest spec wins.

    Part of the reason the ANSI standard was writen was because one LCD manufactuer quoted their "potential light output" measured with the LCD pannel taken out :eek:

    By almeans read the specifications.Compare them against other machines. But go see the images and watch it with a source that you are going to use.
     
  28. uncle eric

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    B4,
    There are so many variables that its very difficult to put a general percentage on this. BUT, its a fact!
    Eric
     

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