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Discussion Starter · #1 ·


I have a FP D-ila setup currently and am planning on going with a RP approach, using Stewarts "Filmscreen 100" or 150 fabric. It is not the optical / lenticular / limited resolution type, but rather quite similar to a FP surface, in that it is a diffusion type.


I will be using 1 mirror, and a screen size of approx. 8.5' wide (16X9 this time I think).


Any comments from anybody using such a setup or experience with same ?


- Thanks,


Chris
 

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I don't think anyone has really done this in the home. I have seen it at shows and it looks pretty good. You might also consider that Blackhawk it was looking very impressive at Infocomm, it's not yet available though. Keep in mind that you will likely want to get an S15 (or possibly an M15) for a rear-projection application.


Regards,


Kam Fung
 

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Discussion Starter · #3 ·


Kfung,


Thanks for the info. I will be using a G-1000D.

I have 12' behind the screen surface - no need for a short throw lens in this case.

The "Blackhawk" is the new Vutec acrylic surface? I had read a little about it, but can't seem to find any real info anywhere. I have controlled lighting so gain is not really needed (or wanted, due to hot-spotting), so as long as ~1K lumens will work for a 8.5' wide 16X9 rear screen, ("gain" of ~1) I think I'll be OK.


Chris.
 

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Chris,


You might want to take another look at the D-ILA calculator. The G1000D has a throw range of 1.9 to 2.85.


To get 8.5' wide (not diagonal) you would need to have at LEAST 16' from lens to screen. If you had a room 12' deep behind your screen, then the distance from the lens will actually be less than 11'.


My G1000 is 17' from my 9' wide screen and that is as big an image as I can get -- the projector is zoomed all the way out.


You can still use a G1000D, rather than an M15 or S15, but you would need to use a mirror system like the Revelation. Or build your own by scavenging an old RPTV for its mirrors.


------------------

*********************

Kirk Ellis

G1000 D-ILA, HTPC, Panamorph (soon I hope),

Dish 6000 (HBOHD,SHOHD,CBS,NBC,ABC,WB,FOX,UPN, KCET -- does it get any better ?)
 

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Discussion Starter · #5 ·


Kirk,


Thanks for the advice. As I said, I would be using one (1) mirror in this arrangement, but am more curious about experiences with screen materials at this point.

Surely somebody is doing this ?


- Chris.
 

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Dizzman,


I'm doing an RP setup as well. Do you have any experience with the flexible diffusion screens? The obvious appeal is their affordability. How is their image quality?


One thing I wonder is if there much to be gained by using the very expensive Blackhawk or expensive Glasfire over a dark tinted flexible screen. I have samples of Glasfire and Jenmar Blackscreen, and while they're great at looking dark in a room with ambient light, they suck up the projector's lumens as well.


Thanks


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Noah
 

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Discussion Starter · #8 ·



My specific questions would be the following, compared to a 1.3 gain front projection surface (currently being used.)


Hot spotting / uniformity of various diffusion / flexible screen materials.


Ambient light rejection


Any possible interaction between projector (D-ila) and screen (such as is the case with "optical" sceens suchs as the common fresnel / lenticular variety) - These screens have a finite resolution of their own, and can introduce moire, herringbone and other similar problems when used with certain projection devices (esp. digital / fixed pattern ones).


Drawbacks of these surfaces -vs- a 1.3 gain FP surface


Actual brightness of the image (in a dark room) compared to the FP surface


Contrast of the image in a partially lighted room (any improvement on the "unwatchable" FP arrangement?)



- If anyone has direct experience with D-ila and RP, I would love to hear what works, what doesn't, and what problems may be created (as well as perhaps the not-so-obvious ones that might be solved / improved).


Thanks


- Chris

 

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I love the idea of RP for my next HT room. It makes sense in so many ways. Unfortunately, I believe this is one area where the DIYer had better get the help of an expert.


Dennis Erskine is one such expert. Well respected and highly experienced, he should be able to answer all the questions above.


I've invited him to comment here. Hopefully he'll have some time.


Chris, I asked him many of the same questions, but I simply said "will it work?". http://www.avsforum.com/ubb/biggrin.gif


My remembrance of the just of his answer was "$$$". http://www.avsforum.com/ubb/eek.gif


A G15 or 20 may have a better chance, but my little G11 probably wouldn't quite cut it.


Chris
 

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Rear projection has several advantages and a few very distinct disadvantages.


On the positive side, you can end up with a nice picture in a room with poor light control, and, since in many cases your screen size is smaller, the picture defects are smaller and far less likely to bother you. From a decorator's perspective...it's an easier fit in a multipurpose room and easier to design multiple use living spaces with RP.


On the negative side; however, is the expense and wasted floor space. The expense is that a good mirror system plus a rear projection screen can require some rather hefty expenses. Equally problematic (in most homes) is that the rear projection set up will take up floor space behind the screen (sometime considerable floor space) to accommodate the projector's throw distance. The least amount of floor space is consumed when you get into multiple mirror systems. When you get into multiple mirror systems, your costs begin to rise.


Using a G11, 15, or G1000 is not really a problem...except for the throw distance. In the case of a 16' throw distance, you're going to eat up 9' (minimum) of space behind the screen that must be completely dark. Six to seven feet with a two mirror system.


Now for a more pragmatic issue. You're spending a ton of money for a very nice projector, mirror, and screen system to end up with a picture not that much larger than a large RPTV. The Scottish side of me suggests that in the absence of a real compelling reason for rear projection, I rather spend slightly less money and end up with a much larger picture...a more theatrical setting. Part of the question is rather you want a TV or a theater feel to the end result.


------------------

D. Erskine

DEsign Cinema Privee
www.DEsignCinema.com

Imagine what you could do, if you could do all you imagine.
 

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Discussion Starter · #11 ·


Dennis,


Thank you for your reply on this matter.


Each of your points is well-taken, however, I would like to actually go LARGER with my proposed RP setup, not smaller. I currently use a 4x3 7.6' wide screen (already quite a bit larger than any "regular" RPTV I am aware of), 1.3 gain, front-projected. I would like to go RP, with a 9'wide 16x9 screen (flexible / diffusion, I think...).

Aside from the increase in size of the pixel structure itself, (not bad on a D-ila), is there some other factor that would imply I could not go with this size screen/projector combination? As it is quite common to use this screen size in a FP setup, I must be missing something as to why this may not be practical in a RP setup.

One of your points above was the wasted space - I have the space; the room is built for this purpose, with a 12'x12' "RP room" behind the screen wall to house the projector, mirror, and some speaker components.

With the space issue solved, what other problems am I not aware of with this particular setup?

Lastly, I would plan to change out the projector as

technology would provide better alternatives in the coming years, and would like to maintain this setup and screen (unless some "miracle" screen surface evolves...), just changing the projector when needed. Is this a practical assumption?


Thank you for your expertise and time on this matter.


- Chris

 

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Chris:


There is nothing inherent in materials like Stewart's Filmscreen 150 (a good choice for DILA) that would prevent you from creating a single mirror system with a 9' wide screen. Generally, glass or acrylic screen material is better suited when ambiant light is a concern; but, that significantly increases the cost.


------------------

D. Erskine

DEsign Cinema Privee
www.DEsignCinema.com

Imagine what you could do, if you could do all you imagine.
 

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Discussion Starter · #13 ·


Dennis,


Again, thanks for your time.


please forgive me for being persistent, but...


Could / Should I expect virtually the same performance (contrast ratio, viewing brightness, uniformity...) on a RP setup using 1 mirror and one of the "filmscreen" gains (150 would be your choice?) as I currently enjoy using the StudioTek 1.30 FP surface ? Obviously upping the screen size slightly will reduce brightness and increase pixel structure, but all things being equal, what, if any, differences in these two projection methods / surfaces will exist ??


- Thank you.



Chris.
 

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Chris,


Sorry, I didn't pick up on the "1 mirror" statement. Have you already tested the single mirror method with a G1000 ?


How does the mirror orient to the projector ? 90 degrees to the light-path (ie, parallel to screen) ? Anything else seems like it would introduce keystone errors with only a single mirror. But ... parallel would mean the edge of the image would be bouncing off the mirror and hitting the front of the projector.


------------------

*********************

Kirk Ellis

G1000 D-ILA, HTPC, Panamorph (soon I hope),

Dish 6000 (HBOHD,SHOHD,CBS,NBC,ABC,WB,FOX,UPN, KCET -- does it get any better ?)
 

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A flat mirror introduces no keystone assuming the projector is at the proper angle. With a single mirror, the projector will have to be tilted from the horizontal at double the tilt angle from vertical of the mirror.


------------------

Noah


[This message has been edited by noah katz (edited 09-10-2001).]
 

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Discussion Starter · #16 ·


Couldn't have said it better myself -- And I am assuming that this will work. No, I haven't actually set it up yet, but I will if I can get some good feedback on what screen surface to go with...


- Chris
 

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I designed a rear projection option for my system a couple of years ago. I was merely going to avoid mirrors and make the rear projection "box" by using the library (which shares a common wall with the theater room) which is seldom used when the theater is in operation. Then I realized that this box needs total light control and really needs to be painted black everywhere. I use front projection as a result. Vince
 

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A lot of effort for something you can buy prepackaged. The Scenium LCOS TV is based on the same technology as D-ILA. If you want more than 50" that might merit reinventing the wheel.
 

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Discussion Starter · #19 ·



Perhaps I am not being clear, but I want to essentially duplicate what I have now, but do it from the other room (not a library or other "used" room) to avoid visible "stuff" hanging from my ceiling, noise, heat, etc...


I just want to know if doing it will change the image I am seeing now. I.E, if the rear proj. diffusion surfaces have the same characteristics as the FP ones do.


I do understand that 50-70" self-contained RPTV's are widely available.


- Chris.
 

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Hi Chris. A while back I spent a lot of time reading the tech papers on RP screens at the Dalite site. Lots of good info about what you're interested in. Because a diffusion-screen surface is so different from a fresnel/lenticular combination, I got the impression image characteristics would differ. From what I read at DaLite the diffusion structure is an extremely thin layer of micron-size 'bubbles'--at least with Dalite's technology. Seems like it would be akin to displaying on a ground-glass surface. As you may have read, some set makers (Runco, I believe) modify certain models with diffusion screens, and some commercial makers of RPTVs for computer graphics also use diffusion for very high resolution. Perhaps forum member Dean Roddey could provide more description. I recall him detailing a lenticular-to-diffusion conversion a while back in another home-theater group. Also, Dalite used to carry a series of magazine articles on its site about conversion to diffusion screen. Recall Roddey described some problems with what might be called 'back splash', which I interpret as light reflecting off the pure white rear surface of a diffusion screen. He may also have commented on the change in viewing angles with diffusion, plus the need for more controlled lighting in the viewing room. I'm sure Stewarts representative can make a good pitch favoring their approach over solid optical diffusion screens, but I'd sure want to see some comparison data and even check it out myself before such a major undertaking. Suspect the Stewart approach is far less expensive, but this might be just the time where you get what you pay for.


I'd considered a D-ILA over a year ago, but the problems of heat and noise (solved with your approach), plus costly bulbs, finally pointed me to a 9-in-CRT RPTV. As I'm sure you realize, the entire adjacent 'projection room' wouldn't have to be pitch black, only the path between the projection lens and the diffusion screen. One could devise some type of light shield. Perhaps the sales folks at Dalite or other rear-screen firms can put you in touch with consultants that handle such installations. Hope you succeed with this approach. I'd like to hear how it looks. -- John




[This message has been edited by John Mason (edited 09-16-2001).]
 
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