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Stacking

Discussion in 'Projectors, Screens & Video Processors' started by buns, Feb 15, 2003.

  1. buns

    buns
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    I know I keep asking crt questions and then circumstances stop me..... so here is another question of that sort!

    I have been to my local cinema quite a bit recently and it has me really starting to notice that the cinema whites are really really bright and there is a wonderful contrast to the picture..... perhaps unsurprisingly my little lcd just cant match that. But hopefully whatever i get to next can get somewhat closer! I hear on and off about stacking crt's. Now I presume the major benefit of this is the brightness. But at what point do such benefits start to appear? Using a 7 foot screen for example..... would a stacked 7 inch set up (sat 2 barco 801's) be a nicer array than a single 8 incher (say a barco 808)? Or is crt just the wrong way to go for a nice bright picture?

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  2. Roland @ B4

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    You wash your mouth out sir.
    there are infact several factors that have to be right to get the same sort of impact from a CRT as you would get at a cinema. In no particular order.
    • screen gain
    • screen size
    • projector age and output
    • source material
    • scaller / doubler
    • genral set up and callibration of all equipment
    I know there's more but the family are calling me.

    Double stacking CRT's is not easy. I'm only aware of 2 installations in the UK. There are very few techs in the UK who can do it (I'm 0ne) and keeping two projectors aligned is more than twice the work.
    Those of you who came up to the Manchester show last year with have seen my set up in the Denon room.
    I'm confient we are going to do it again at Bristol but we may go with a flown projector to get more seats in the room.

    Double stacking 801s will not be as bright as an 808s.
     
  3. buns

    buns
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    Sorry! The incessant throwing of spanners in my works forces me to say such things!

    I think your last line basically answered my question.... so i presume stacking is just something for those on mega budgets?

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  4. Roland @ B4

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    And those with nothing better to do
     
  5. Phaeritt

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    Hi Guys,
    I've been reading Roland's replies to multiple CRT stacking threads and was wondering if anyone could expand on a topic that he mentioned. I've just purchased a second Electrohome 8501 (8" CRT), and intend to try stacking my two projectors. I've done considerable work in preparation for ceiling installation, so I am currently planning to horizontally stack the two units, but it's not too late to redesign things so as to vertically stack them. It was mentioned in another thread that swapping the red and blue CRT's in one unit could help reduce color shift. I assume (incorrectly?) that this is more effective in vertically stacked arrangements. What degree of improvement have you noticed with this technique in your experience?
    Btw, both units have ACON (automatic convergence) boards, but only one has a working sensor for ACON; I expect the current wear on the CRT's to be significantly different until I can replace them all around, and I do have nothing better to do with my time than play with convergence. I'm hoping for a 102 to 120" wide screen (maybe 1.3 gain), but haven't selected one yet.
    Thanks for all the help these threads have already given me!
     
  6. KarlRobinson

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    Roland, not meaning to pay detriment to your skills but;

    In my mind why would it be any harder to converge and align two projectors over one. I appreciate they can loose convergence but a single projector can do this and I see two just being twice as hard.

    Enlighten me.
     
  7. Roland @ B4

    Roland @ B4
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    It's not just the convergence that is the problem.

    It is extreemly rare to find two projectors with exactly the same geometry characteristics (particulary linearity).

    Most people recon to pull the projector back a little to give them selves a bit more ajustment.
    It is more than twice as hard I can asure you. Keeping the red aligned with green is bad enough keeping it alligned with another green and a couple of blues can be nasty.
    Each projector has its own colour shifts and gamma curves which can be tweeked in the menus but add a projector that may have completely the opposite shifts can add some strange colours.

    A double stacked image is brighter but is always softer because you can never exactly alighn the images.

    One, but preferabley both machines should have a convergence on green module fitted or you will never get it right.

    If you have two machines have a go.
    The way I set them up has always been stacked but side by side will work too. but a working and not working machne makes a huge differnce to the magnetic field so expect some differences if you don't power one of them up.


    rotating the Red and blue will help with colour shift in either stcked or S by S. Putting the blues in the middle seems favorite though I'm not 100% sure that it makes so much difference.
     
  8. Joe Fernand

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    Hey Roland

    Maybe only two permanently installed Home Theatre installations but I bet there are hundreds of stacked rigs used every week at Conference, Exhibition and Event gigs around the UK.

    Most large AV hire companies will carry Chief or other stacking rigs in there hire fleet and many of the 'Roadie' type projectors are designed for stacking with interlinking command and control cabling and line up mechanisms.

    The 'old timers' in the freelance Tech world were so used to playing with twelve or more stacked and racked 35mm slide projectors that one CRT/LCD/DLP is just not enough of a challenge on a Conference rig.

    I'm sure though that not of the temporary rigs have anywhere near enough time and care spent on them.

    Best regards

    Joe
     
  9. Matinee

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    Stacking several 35mm projectors using one bulb each is not the same as converging 3x(number of projectors) light sources.

    PK
     
  10. Joe Fernand

    Joe Fernand
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    Matinee

    Possibly true - but how quickly could you rearrange a multi projector slide show that's trayed up when the customers asks you to remove one slide :)

    I'm also sure that a few of the old timers will tell you that getting a multiple 35mm projection rig lined up is no easy task - a well set up slide rig with carefully produced slides and a well programmed dissolve unit looks fantsatic (though a tad noisy).

    And try and get a single CRT to look as bright as a high output 35mm slide projector - hence the double stacking of CRT's.

    Best regards

    Joe
     
  11. Roland @ B4

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    The differnce between doublining up for extra brightness at a confrence in a high ambient light environment. and stacking for a home cinema are physically the same. But what the two environments will accept as a satifactory picture are not the same by a long way.

    I've done my share of LCD and 35mm stacking give me one of those to do any day over a CRT. You are dealing with a fixed frame device provided the projectors are parallel its just a matter of lens shift.

    CRT are not linear devices nor are the ways they drift. getting a brighter picture is easy getting it to look like a single image just brighter is not so funny. Getting it to stay that way takes a long time.
     
  12. Joe Fernand

    Joe Fernand
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    Hello Roland

    So given that someone (Buns) is contemplating going down this route how often are they going to have to invite you over for tea?

    I guess the answer for Buns is to get the 'best' CRT he can at this time and upgrade it as and when funds are available and avoid contemplating stacking a second 'matching' CRT on his first CRT.

    Best regards

    Joe
     
  13. buns

    buns
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    I wasnt seriously considering..... but ive spend so long in contemplation as repeatedly my efforts failed that i just wanted to know what the comparison of stacking against a bettere projector would be..... which i beleive roland told me was the better machine! and since he knows best im not going to argue!

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  14. Roland @ B4

    Roland @ B4
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    I very much doubt that's true.
    My father had a saying "If you can't be right, be certain" pretty much gets me through most things.
    Happy to converge for cake
     

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