Wall to wall screen

Discussion in 'Home Cinema Buying & Building' started by xxGBHxx, Jan 11, 2019.

  1. xxGBHxx

    xxGBHxx
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    Hi,

    After 2 years of waiting, pain, suffering, building disasters and life getting in the way I'm finally just about ready to start building the cinema I thought I'd have finished 2 years ago.

    I will have a lot of other questions in the near future but todays relates to the screen.

    It's a dedicated room with an AT screen. I've looked through a few hundred room pictures all over the place and one thing that struck me was screens are rarely, if ever "wall to wall". I had planned to pretty much fill the entire wall with a screen to within about 10-20cm each side (within ratio) but I'm starting to doubt it. If I go to a cinema, the screens are almost always floor to ceiling and wall to wall, especially so with Imax so why do people chose to have these tiny 90" screens on a wall that could take 150+?

    Now I appreciate it affects brightness but ultimately it's going to be a pitch black room where the only focus is going to be the screen so are there any pitfalls or issues I'm missing by filling the entire wall with a screen?

    G
     
  2. Cherrywood

    Cherrywood
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    There is a number of factors you need to consider -
    > Projector Throw - you need to work out what size screen for your chosen PJ in relation to distance from screen.
    > Seating distance - a site like the following might be a good starting point, if you are having rows i would priortise you MLP and added further seating around that. Viewing Distance Calculator
    > Screen Ratio - this will depend what content you will be watching. If Gaming/ TV Boxsets / Sports then 16:9, if more films then 21:9. Personally as you are going for a AT Screen i would look at building DIY 16:9 screen and then creating masking (auto or manual) to use for with 21:9 ratio. (You will need to look for a PJ with lens memory Epson TW9300/TW9400 would be a good starting point)
     
  3. Peter Parker

    Peter Parker
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    Hi G,

    My screen is wall to wall - no gap between the screen surface and the walls.

    The problems you can get with the screen being close to surfaces is that the screen will reflect light onto those surfaces and then that light will reflect back onto the screen, and that can cause a loss if intra image contrast as the bright parts wash out the dark parts. The remedy for that is to make sure the surfaces are as non reflective as possible - black velvet works well in doing that. if you don't want to use black velvet, then a grey screen or a grey ALR screen may be the next best option

    The brightness of the image is determined by the lumen output, screen area and any screen gain, so it can be calculated.

    HDR requires a lot of lumens, but as projectors are never going to be as bright as a flat panel, HDR is compromised anyway. You can still get HDR on a dim screen, it just won't have the same 'pop' as on a flat panel. If you're not bothered about HDR so much then you can go as large as you can. But:

    Viewing angles are important (for immersion as well as viewing comfort), and that's determined by how far you sit from the screen and how much you have to look up at the screen. In one respect, screen size is irrelevant - no good having a big screen if you're still sitting too far back. 150" diag screen from 20 feet back is going to look smaller than a 100" diag screen from 10 feet back, so planning your seating distance is more important. After that you can determine where the speakers are going to go. You may want to look into using REW (Room Eq Wizard) to simulate the best position for subs in relation to the seating as well (and make sure you're not sitting in a nul).
     
  4. xxGBHxx

    xxGBHxx
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    OK.

    Didn't want to go into it too deeply but theres some great advice that deserves some context.

    The room is 5.5*3.2*2 (yes that's about 6ft 7 Inches). There are some pretty nasty compromises I have to make because of the orientation of the room and the location of doors.

    There is going to be 2 rows of 3 seats and the front row is going to be about 2.7m from the screen. Behind the screen are 3 alcoves with the subs sitting centre bottom.

    Speakers are going to be a complete and utter nightmare as although it's a dedicated room it's very complicated as far as placement is concerned. I've done a REW room plot for the 2 subs but the dimensions make things REALLY difficult. I get a huge 40-50Hz null roughly 2.9-3.6m back so I need to make sure the seating avoids these points. I have a UMIC-1 ready to go to calibrate and test.

    I've done the calcs on the Epson and it gives around the output I want onto a 120" wide screen. I am still flip flopping over whether it's 16/9 or 1:2.40 and I still haven't made up my mind. I'm VERY tempted to go 16:9 as you say and mask as I always reconcile that gives me the maximum for 16:9 as well as the maximum for scope. If I go completely scope then the side masking makes the screen that much smaller. My throw will be about 5m so the 9300 should be more than enough for the job in a pitch black room. I did calculate the values about 2 years ago and I did get more than enough for half decent HDR.

    Finally I am looking to create a perfectly black (probably velvet lined) 1m zone in front of the screen to stop reflections as best I can. The reason for this post was as much a sanity check to make sure I'd not missed something. If at least one person has gone wall to wall and is happy then so am I.

    The more I think about the masking the more I want to do it motorised but I've yet to find a completely clear step by step guide. Anyone found one?

    G
     
  5. Peter Parker

    Peter Parker
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    If you want to do CIH you have to make sure your seating is determined by the screen height so that 16:9 doesn't look too small - you set the seating to achieve the viewing angles that work for you. Your suggested front row of 2.7m (106 inches) is very close to 2x the screen height which I think is ideal for CIH (or even CIH+IMAX), and your 16:9 image shouldn't look too small.

    Side masking for scope can be as simple as corded curtain track, so doesn't have to take up much side space if the masking only goes down to 16:9 - 15 ins of material can fold into a much narrower space (electric may take up more space - I've not tried it so can't really help there). You may need to put a piece of dowelling down the leading edge for a nice straight finish. Masking could even be panels made from wooden batons with velvet stretched and stapled over it, and manual fitted/removed as needed. They don't require any additional room each side of the screen.

    The CIH + IMAX option is to fit the 120" wide 16:9 screen but mask it for 2.40 and watch everything CIH. If you then have an aspect changing movie like TDK etc, you just remove the top and bottom masking and zoom the image to fit like you did for all the other ratios when the masking was in place. That way IMAX is taller then scope and different to 16:9, just like in a real IMAX theatre.

    The height of your second row riser may be a bit of an issue with the low ceiling and the projector being ceiling mounted. You could stagger the second row by having two seats (rather than 3) aiming through the gaps of the front three if you wanted to keep the height manageable. Making sure the front row heads don;t mask too much of the bottom of the screen is something to calculate for - there are online calculators out there which should help.
     
  6. Luminated67

    Luminated67
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    2.7m from the screen is close, I am 3m back from a 100” screen and wouldn’t want it any bigger unless in CinemaScope.
     
  7. xxGBHxx

    xxGBHxx
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    I am confused.

    Sorry, isn't a 16:9 screen masked to make a 2.40:1 screen CIW? That is don't you mask the top and bottom to hide the black bars? Perhaps I'm missing something but my understanding was you "zoom in" to max the image for a 16:9 then you "zoom out" to display the 2.40:1 and then mark top and bottom.

    Not had the opportunity to play with my projector so can only assume but that's always how I understood it.

    Yes I've done the calculations for head clearance etc. but it is going to be a little close to the ceiling but that's what I have unfortunately. It's going to be a number of compromises along the way on this as it's just not an ideal area to do it in (the location of a door and the stairs make it even more difficult as I am very limited on seat placement as well).

    Ok thanks, I just needed to know about the wall to wall screen at the moment, the rest will come over the next few months as I try and shoehorn this into the space I have.

    G
     
  8. xxGBHxx

    xxGBHxx
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    Thanks.

    But when you go to the cinema for Imax or the larger screens they have in the Superscreen cinemas you're way closer/larger than that? Why do you feel it's too close and/or too big?

    G
     
  9. Luminated67

    Luminated67
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    I prefer to be able to see everything in my vision, when too close to a very large screen your eyes are constantly darting all over the place trying to see all the action unfolding, for me this gives me eye strain. In 16:9 I feel this is worse and in CinemaScope which is why I say me personally I could stretch screen size a little more but only in that formate.

    Your ideal of wall to wall I actually agree with and would be class just think you need to rethink your seat position unless you intend to sit primarily in the second row.
     
  10. xxGBHxx

    xxGBHxx
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    Ok hard to explain and really need a different post but heres a quick paint drawing to illustrate (as theres a lot of issues around this I'm going to need to sort over the coming months so I'll make a dedicated post for it)



    [​IMG]

    So what this (terrible) rough drawing shows is the screen in red MUST go against that far wall because the door in the opposite wall has to be accessible and the alcoves at the screen end lend themselves very well to an AT screen (it's actually 3 alcoves not 2 as shown). Coming down into the room are the stairs from the ground floor that jut out and extend into the room a single step so it makes putting chairs adjacent to the step incredibly difficult.

    Now I MIGHT be able to get 3 chairs in along side the step which would make it about 3.5m back but then I'd probably have to compromise on the type of seating (pretty certain I can't get 3 reclining chairs in unless I use almost the full room width. I could put a single row in at the back wall but the intention of the cinema is to have guests and it also makes speaker placement even harder. I also have some very nasty bass nulls around 2.7-3.6 (pretty much where the step is) according to REW I have to avoid.

    It's going to be very tricky to get this all placed right and one of those compromises if I want 2 rows and reclined seating is going to have to be closer than I think anyone would like.

    Thanks again though for the input gets my mind working!

    G
     
  11. KelvinS1965

    KelvinS1965
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    Well you already said brightness, but also quality: You need to use a lot of zoom to fill a screen that size, especially from a short throw, so you'll be using max zoom. This does help a little on the brightness front (due to lens aperture change), but you're more likely to get a softer image this way, especially with budget projectors as you can't use the sweet spot in the centre of the lens.

    Also if you go to 150" wall to wall, it would have to be AT and they tend to have less gain than non At screens, so this just further compounds the brightness issue. You can of course watch a dim image in a pitch black room and in fact when I first got a light meter I found I'd been watching at around 5fL (typical for SDR is more like 12-14fL). Now I can manage to comfortably hit 14fL, the image has more punch to it and I don't feel that the black level has suffered (I still can't 'see' a fade to black for a good 4-5 seconds, by which time the scene has usually changed to a bright one again).

    FWIW I've ended up with a slightly smaller viewing angle since I re-did my room and changed ends. Like you I have a door and have to put the seating further back than would be ideal if it were a dedicated room. 3m wide scope screen from 4.5 metres back still looks good though and going AT was one of the biggest improvements I've made over the years.
     
  12. xxGBHxx

    xxGBHxx
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    Going by the calculator on Projector Central (I have *NO* idea how accurate it is) into a room with a 5m throw, no more than 15% ambient light on a 130" 16:9 diagonal screen I should get in the region of 40fl. Now I'm sure the reality in eco and movie mode will be considerably less but I should still hit 15-20 I hope. The recommended seating distance is about 4-6m which obviously causes me issues but I've read a few people remarking they don't agree with those distance calculators.

    It's all very interesting.

    G
     
  13. Peter Parker

    Peter Parker
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    Not in this case, no, It would be CIW if you were showing everything at the same width, but you won't be doing that. Everything will be CIH except for the occasional IMAX presentation (if you do it that way). All content will be the same height but the width will vary, whether it be 2:1, 2.2:1 1.85:1 etc. When you see an IMAX movie at an IMAX theatre, those movies are scope with additional top and bottom content added from time to time throughout the movie. If you do CIH+IMAX, everything except for IMAX will be CIH, and the top and bottom masking only comes off for IMAX presentations. This way you also differentiate between 16:9 and IMAX which aren't supposed to be viewed at the same size. Hope that makes sense.

    I went the DIY route so my screen is the perfect size for my room, if you don't mind cutting wood etc, you can get good results for little cost compared to a bought screen. It's not for everyone though.
     
  14. Peter Parker

    Peter Parker
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    Not everyone likes to sit close, so have their own preferences. I'm at 2x the screen height (so a little closer then you will be), and it works fine for me, and I also have two rows of seats. IMAX has most people sitting even closer.

    We have a binocular horizontal field of view that is around 120 degrees, when you're sat at 2xSH with a scope screen, you will have approx a 61 degree field of view - around 50% of what you can see without having to move your eyes. You can and will move your eyes of course, but it won't be much. With IMAX theatres most people will have a wider field of view - they actually advertise a horizontal viewing angle of 70 degrees which is more then you or I have. At 2xSH for scope, when you take of the top and bottom masking for IMAX, you will have a seating distance ratio of 1.5xSH which is around the back row of an IMAX theatre, so you will be replicating the IMAX experience on a smaller scale, but with the same image size on your retina,

    Vertical viewing angles are more critical, where looking up should be no more then 15 degrees, and a max allowable of 35 degrees. With IMAX they usually don't have content that you need to look up for above the main scope area, but if they do, it's not for long, otherwise people will get neck ache. Most regular IMAX patrons will tell you to 'sit high' because of the increased vertical viewing angle for the movies scope content (so sit above the centre of the seating area).

    If you can test by firing up the pj and projecting onto the wall to get an idea fo what to except visually, you'll get a better idea of what your proposed set up will work like.
     
  15. xxGBHxx

    xxGBHxx
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    Still not sure I get CIW/CIH as although I know exactly what the terms mean in concept I clearly have them mixed up from a practical point of view. Regardless of what I do the frame needs building before then anyway and it's going to support whatever I chose to do in the end. In the interim I will go Googling and re-read what I thought it meant.

    I did fire up the projector about 18 months ago balanced on top of a bale of Rockwool and it was glorious onto a white bedsheet ;)

    It's more like a building site down there than a room atm so no option to take it out quite yet. As for building the screen I will be doing most of that. I've been building most of the house as it is and I have all the tools so will be a "doddle" compared to some of the other stuff I've been doing. While I think about it, where's the best place to get 4k AT screen material from at a reasonable price?

    That said, before I get there I have to sort out the false walls - thats a story for another thread though...

    Thanks again

    G
     
  16. Peter Parker

    Peter Parker
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    If you only had a 2.40:1 screen with no top and bottom masking and no IMAX option, it would be CIH wouldn't it? Only the width changes, the height remains constant. :)

    With CIW, ALL the smaller formats are shown larger than the largest format (scope) - the height changes but the width doesn't, that remains constant.

    Just because you add an IMAX option doesn't then make the CIH part CIW.

    Hope you get it how you want it and enjoy building it as much as I did mine :)
     
  17. xxGBHxx

    xxGBHxx
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    Yeh I think we were both right ;)

    I was thinking of putting in a 16:9 in and then masking for scope (CIW) but you were putting in scope and then masking for 16:9. My fault for not reading properly.

    If I hadn't just spent the best part of 2 years doing DIY almost every waking hour I think I would. Right now I just want the pain to stop. Admittedly it's more fun than doing the utility room or music room but it's jsut a long long road to get here and far far longer than I'd planned or envisaged :/

    Once I star tin earnest I will post a thread of the progress. Who knows I might be able to help someone else.

    G
     
  18. Peter Parker

    Peter Parker
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    I have a wall to wall 16:9 screen that is masked down to scope. I also use an anamorphic lens, so nothing is taller than the scope screen height, and I watch everything CIH.

    Except for IMAX. For that I remove the top and bottom masking. That way, the height relationship is correctly maintained for all formats, as is the immersion and intent of each format. Over the past two years, I've only had to remove the masking for three IMAX movies - Tron Legacy, Dunkirk and Mission Impossible: Fallout.

    I did much the same for my place. The cinema room was the last room I built and has only been up and running for the past two years. It also took me a lot longer to get there than I expected :)
     

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