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Torus for blend setup
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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Sun May 25, 2014 12:37 pm    Post subject: Torus for blend setup Reply with quote


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Hi folks,
i want to do an ambitioned project.
I have 2 Marquee 8500 Ultra with P43 greens, HD8B uncorrected lenses.
They should work togehter in an edge blend.
My room is limited, so a screen 16/9 3,12m wide (10,24ft) with a curvature of 20cm (7.9inch) is the maximum.
The thing is i want to do shutter 3D. So every tiny amount of light is welcome.
I downloaded the torus calculator http://www.avsforum.com/t/467141/this-is-what-ive-been-working-on/120#post5627244 and played with it.
My seating distance is variable, but 3.5m (11.5ft) at the moment.
The projectors will be ceiling mounted.
If i get 2 sets of HD144 or HD145 lenses, it will affect throw.
I can live with that, i can mount the projectors everywhere on the ceiling.
But will this affect torus curvature or anything else too?
I'm not sure about it, never have doen something that complicated.

One more problem: I searched for various screen material, but nearly everything that you use here, isn't available in Germany.
Maybe someone living in Germany (or at least Europe) can give me a hint.
What material would you recommend? Which gain should be best?
I'd rather run my projectors at 20 contrast than at 75, if it should be too dark for shutter when it's finished.
Maybe it would be nice to have some silver coated screen material, it is not impossible, that i want to try polarisation 3D later.

Regards, Julian

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garyfritz



Joined: 08 Apr 2006
Posts: 10670
Location: Fort Collins, CO


PostLink    Posted: Sun May 25, 2014 2:11 pm    Post subject: Reply with quote

I think you're trying to stretch the technology far beyond what it's capable of.

* Blending by itself is a huge challenge.
* A torus is a big challenge, and I'm not sure a torus is compatible with blending. A torus needs a high-gain screen to focus the light. I think blending really requires a unity-gain screen, or else you get different reflectivity from the two projectors.
* 3D is a bit of a challenge.

Put all those together and I think you're asking for trouble.

If you have 20% overlap on the screens, each 8500 will be projecting 3.12m / 2 / 0.8 = 1.95m wide. So its effective 4:3 area will be 1.95m x 1.46m = 2.85m^2. That's 6.4' x 4.8' = 30.72 ft^2. That's a small image so you will get good brightness out of it. The 8500 is rated for 1200 peak lumens, so 1200 / 30.72 = 39 ftL with a unity-gain screen. That's PLENTY bright, even when you cut it in half for shutter 3D, so you would be able to run at lower contrast like you want.

If you want the big 3D, I would skip the torus. You might have to run your contrast at 50 instead of 20, but an 8500 will run forever at that level. For corner focus, blending, etc, a flat screen would be MUCH simpler than a torus. And it's a whole lot easier to hang a flat screen than to build a torus. And you would also avoid all the issues of high-gain screens (hot spots, limited seating area, etc).
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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Sun May 25, 2014 4:14 pm    Post subject: Reply with quote

So if you think a white flat screen would be enough.. what gain should i use?
1? Btw: i didn't want to use Gain 10 or so, 2-3 seemed right, i think.
But tell me more. If i achieve 16 or more ft Lambert, after passing the glasses, i should be right.

You have a mistake in your calculation: The height (16/9) will be 175.5cm, ending up in 195x175.5cm=3.42 m².
Thats 36.8ft². 1200lumen/36.8ft²=32ftL. I think this describes a 1.0gain screen.
The light loss will be about 60% for 3D (if it works well), so 0.4x32ftL= 12ftL behind the glasses.
Is that enough?
If i do now calculate it with another gain, can i simply multiply the number with the gain?
E.g. 12ftLx1.3 gain= 15.6ftL

And i think 1200 peak white lumen means 1200lumen at max settings.
That is about contrast 80 when the beam current limiter kicks in. Not a good idea to run the projector that high.
If i am wrong, please corret me, i'm here to learn.

Thank you, Julian

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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Sun May 25, 2014 9:38 pm    Post subject: Reply with quote

I just have to say that. Went to the cinema to watch that new Johnny Depp movie tonight.
Very small room, about 25 seats and a huge DLP machine projects on a ... white wall!!
Yes, with flat wallpaper on it, a painted black frame around, uneven filler on the "screen" surface...
The projection even didn't fit in the frame and the room was not rectangular.
So you had an angeled view to the screen, even from the middle seats.
Sometimes i wonder why we care so much about screens Very Happy This thing even looked good and uniform.
Yes i know it is logical, gain 1 on a matte surface, projector with high lumens.
Works. But it was good for a laugh.

Maybe it would be a good challenge for me. Finish my own living room cinema
and invite the cinema owner to watch a movie at my place.
Regards, Julian

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garyfritz



Joined: 08 Apr 2006
Posts: 10670
Location: Fort Collins, CO


PostLink    Posted: Mon May 26, 2014 2:50 am    Post subject: Reply with quote

tschaeikaei wrote:
So if you think a white flat screen would be enough.. what gain should i use?
1? Btw: i didn't want to use Gain 10 or so, 2-3 seemed right, i think.

Gain 10 is practically a mirror!! Laughing 3 is a high gain screen. It would hotspot horribly. You can use it in a torus to focus the hotspot on a small viewing area, producing much higher brightness at that small viewing area. But it's a pain to build the screen, get it focused right, etc.

On the flat screen I would say 1.0 - 1.3.

Quote:
You have a mistake in your calculation: The height (16/9) will be 175.5cm, ending up in 195x175.5cm=3.42 m².

The height of the **image area** is irrelevant for ftL calculation. If you look at the image area, then you don't get to use the whole 1200 lumens -- you have to use a percentage of the 1200 corresponding to the percentage of the tube face that you're using.

It's simplest to use the full 1200 lumens and assume a 4:3 projected image. You look at how wide an area you project to, which determines how many square feet the 1200 lumens are spread across. The whole 4:3 tube face is capable of delivering 1200 (well actually the whole tube isn't, that would be ANSI lumens, but you have to calculate assuming the whole tube face), so you have to look at the 4:3 screen area it would cover. If the 4:3 tube is displaying 3.12 / 2 / 0.8 = 1.95m = 6.4' wide, then the 1200 lumens are being spread across a 4:3 are 6.4' wide. If you only use part of the screen, that doesn't make the tube brighter. (Well actually it does, because of current limitations. But for ftL calculations you look at the full 4:3 tube lumens delivered onto an equivalent 4:3 screen.)

So the 4:3 tube is projecting 6.4' wide, meaning the 4:3 area is 6.4*3/4 = 4.8' high, total of 6.4*4.8 = 30.72 ft^2. 1200 / 30.72 = 39 ftL on a 1.0 gain screen.

Quote:
If i do now calculate it with another gain, can i simply multiply the number with the gain?
E.g. 12ftLx1.3 gain= 15.6ftL

Right.

Quote:
And i think 1200 peak white lumen means 1200lumen at max settings.
That is about contrast 80 when the beam current limiter kicks in.

ANSI lumens basically describe the brightness if the whole screen is white. For digital projectors that's no problem -- they're the same brightness whether one pixel is white or the whole screen is white. Peak lumens = ANSI lumens for a digital.

CRT's don't do that because of current limitation. A small area of white (on a black background) can be much brighter than a full screen of white. There isn't enough current to drive the whole screen as bright as a small area of white.

The 1200 "peak lumens" describes the lumens when a small area is white -- 10% or 20% of the screen area, I think. The 8500 is rated at 1200 "peak" lumens but only 225 ANSI lumens. The small area can be more than 5x larger than a full-white image. This is why largely-white scenes (like Ice Age) tend to look dim and lifeless on a CRT but have lots of pop on a digital.

If you can run your projectors at low contrast, not only will you extend the tube life, but I think you'll also have a more vibrant image because you won't be current-limited. Or at least not as soon. With your 30.72 ft^2 4:3 screen area, you could get 225/30.72 = 7.32 **ANSI** lumens -- maybe more since you wouldn't be using the whole 4:3 tube face -- which would look great in bright scenes. In dim scenes it might be too dark, but in dim scenes the CRT isn't current-limited so it would probably still look great.

How that's going to work with 3D, I have no idea.
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Spanky Ham



Joined: 22 Mar 2006
Posts: 5634
Location: Comedy Central


PostLink    Posted: Mon May 26, 2014 4:22 am    Post subject: Reply with quote

I was going to let this go, but Gary chimed in.

Trying to do a Torus blend is a difficult challenge that I don't even think Nash would want to tackle. Is it possible? Yes, I saw one set up at VDC although it wasn't working. Is it going to take a substantial amount of time? Probably exponentially more than a regular blend. Also, don't forget about the expense.

I think a stack would work just fine. I am not sure you could do a stack with a Torus, but you could try. TSE told me a nice trick that you could try with a stack. Since red doesn't wear as quickly as green or blue, you could use either three green or three blue tubes by replacing one of the reds.
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Nashou66



Joined: 12 Jan 2007
Posts: 16170
Location: West Seneca NY


PostLink    Posted: Mon May 26, 2014 1:54 pm    Post subject: Reply with quote

Guys, blends work fine on curved screens!!! Look at all the domed blended simulators out there. They make DM Marquee's , DM stands for domed , those had more geometry controls for the dome. A ST in the model number means Stereoscopic and a LB stands for LongBow. There are other designations out there.

So a slightly curved screen in a blend can be done. If I had the correct lenses Id give it a shot. But maybe with a 3-5 inch curve.

nashou

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garyfritz



Joined: 08 Apr 2006
Posts: 10670
Location: Fort Collins, CO


PostLink    Posted: Mon May 26, 2014 2:00 pm    Post subject: Reply with quote

CAN be done with the right lenses &etc, vs. practical with stock 8500's? I still suspect it would be a serious headache. But you have a lot more blend experience than I do (zero Smile).

Spanky Ham wrote:
TSE told me a nice trick that you could try with a stack. Since red doesn't wear as quickly as green or blue, you could use either three green or three blue tubes by replacing one of the reds.

Cute trick! I'm not sure how well the red would last if you were driving it 2x as hard as everything else, but it would sure give you more life on your blue or green.

Good point on the stack. Julian, if you're determined to do a torus, a stack would be more manageable than a blend. But of course 3.12m wide with an 8500 is really stretching those photons across a big area, so you'd NEED a stack and a torus. Let's see, 3.12m would be a 4:3 equivalent of 10.2' x 5.7' = 58 ft^2, 1200 / 58 = 20.7 ftL ... hang on. That can't be right.

On my 7.1 x 4' screen I get something like 12 ftL. 7.1*4 = 28.4, 1200 / 28.4 = 42+ !? But I'm sure that formula is right. ftL = lumens / squarefeet, one ftL = one lumen per square foot. So I'm not quite sure what's wrong with my numbers. (According to this post, the problem is in the inflated "peak lumen" number.)

My apparently-faulty math aside, however, I seem to recall the 8500 is not a good candidate for a stack. Don't remember why but I think it can't handle the geometry. A blend is probably the only option.

I suspect a single 8500 on a torus might give you enough brightness for 3D (in a small sweet-spot seating area), and it would be a helluva lot cheaper and easier to manage than a blend. That, or a blend on a flat 1.0-gain screen, would probably be your best options.
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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Mon May 26, 2014 4:45 pm    Post subject: Reply with quote

Yeah guys, i knew our blending master would give us some cents.
Thinking about dome installations: 2 or more projectors, edge blended in a heavy curvature application.
We all know it works. But, i don't need it that heavy. And i really think i don't need 10 gain (if i expressed myself ambiguous).

Athanasios, if i get this right, you would try a curved or torus screen with the right lenses (which lenses do you mean?)
and that would only have a 3-5inch depth? So, i have 3.12m (10.2ft) wide screen, if i go 3-5 inch deep in the middle,
would that even be a noticable curvature? I tried a quick setup with a white paper sticking out at the corners about 8.6 inch
and that didn't affect focus. It was a quick setup with astig beeing out of perfect, but focus wasn't worse than on a flat screen.

So, if i estimate the maximum achievable horizontal curve, i end up at approximately 6-7inch. Maybe more, but i don't think it's necessary to use the maximum.
I made some drawings, maybe you all could look at them while i read (and hopefully understand) all the numbers Gary posted. Smile

Spanky; i think the stacking idea isn't too bad, but to be honest... i don't like it.
The projected image will be 16/9 or 2.35/1, so i would get horrible tubemasks using a stack (or a single projector).
Half of 16/9 is about square (adding the 20% blend zone) and half of 2.35/1 is about 4:3.
That seems to be a very tube-friendly solution. And we all like our tubes, don't we?
One more: Dirft (all CRTs drift, be honest).
The projectors are stacked, and one drifts to the left, one to the right. I don't want to imagine how the picture will look like.
Like polarisation 3D with the glasses off the nose? Bah...

One more time: I didn't do that before, these are theoretical thoughts, not experience. Correct me if i'm wrong (otherwise not Razz)


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garyfritz



Joined: 08 Apr 2006
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PostLink    Posted: Mon May 26, 2014 6:16 pm    Post subject: Reply with quote

One thing to remember: the middle picture, with the flat screen, won't have reflective properties like that. With flat screens you use low-gain surfaces, ideally 1.0 or even lower. You can go as high as 1.3 but you'll have some hot-spotting. (I have a 1.3 screen and there is noticeable hotspotting.)

Low-gain surfaces scatter light pretty uniformly. So the mirror-reflective lines you drew don't really reflect reality. (see what I did there Smile) With a 1.0-gain screen you should have almost uniform light scatter, regardless of the angle of incidence.
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Nashou66



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PostLink    Posted: Mon May 26, 2014 7:09 pm    Post subject: Reply with quote

Projectors should be perpendicular to center of the 4x3 section of screen like this.


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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Mon May 26, 2014 8:19 pm    Post subject: Reply with quote

Yes Gary, you are sure right about the 1 gain screen and uniform reflecting.
But i wanted to compare flat and curved (or torus, but from the upper view, it is the same).
I didn't really care about the gain or its effect while drawing this. It is just meant to understand how light is reflected by a torus vs. a flat "mirror".

Quote:
The 1200 Lumen rating is either A)misleading or B) just stupid. That rating usually comes from a 10% white window.
I don't know about you, but I watch movies not 10% white windows. On a movie, a 9" PJ on a 16:9 screen will deliver
under 200 lumens on a high APL scene. On a 50% APL scene they can deliver a bit over 250 or so.

That is what you meant, right? Will calculate the whole thing again tomorrow. Now i'll take a shower and go to bed.
About that:

Quote:
I seem to recall the 8500 is not a good candidate for a stack. Don't remember why but I think it can't handle the geometry.
A blend is probably the only option.

That's ok for me, in case i won't do a stack. But for the understanding, i think keystone would be the problem?
I didn't fire up the Marquees for quite half a year now, don't remember how much keystone would be doable,
but either way, i will not stack.

Quote:
I suspect a single 8500 on a torus might give you enough brightness for 3D

Oh, yes i know that. But what should i do with the other one? Thats the whole problem Very Happy
Yes, joking. But why not? If there will be no effort in blending, one projector will serve as a flower placing box or
mini coffee table. But this is the worst case. Smile

Athansios: Yes, that angled projector setup is really plausible. Have to draw another pic about that tomorrow.
So, as you seem to be a fan of torusses, do you maybe build one yourself in the not too far future?

Again the question about lenses: Which lenses would you recommend for two 8500 blended with a curved/torus?
And what curvature should be possible with standard (HD8B /HD144/HD145) lenses?



Found something interesting on the AVS forums: this is what i've been working on
Second post:

Quote:
garyfritz, the curve should be exactly the same across the face of the screen relative to the center of the green tube. Think of a sphere with the radius being the projector's throw distance. What you're effectively doing is cutting out a rectangle on the outside of that sphere for the screen. Every point in the curved plane is exactly the same distance from the center (green tube). Based on that, the depth at the center of the screen will be exactly the same as the height of one of the corners of the screen.
.

I don't think this counts for a dual projector setup, but who knows... the curve would be small. Will do the math tomorrow.

Regards (and thank you very much (don't know how often i said that here on the forums))
Julian

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hansilili



Joined: 09 Mar 2007
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PostLink    Posted: Tue May 27, 2014 6:42 am    Post subject: Reply with quote

Julian,

if I were you, I would just stop thinking about saving tube life by driving them at low contrast. You have plenty of other objectives. If an impressive picture is one of them then tube wear is the price to pay. If you don't focus on at least one priority (torus or large or 3D or blend) then you might end up in totally dropping the project and having nothing.

In order to get the same light output I'd rather run a single projector hard than a stack in idle. Total installations lifetime will probably be the same as tube wear is not the only problem that can occur in the next years. (Competition from cheaper and better digital projectors beeing only one threat)

My tubes are blooming ince 3000 h and when they are through I just put in the next ones.

Cheers rumpeli

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tschaeikaei



Joined: 08 Apr 2013
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PostLink    Posted: Tue May 27, 2014 6:37 pm    Post subject: Reply with quote

Quote:
if I were you, I would just stop thinking about saving tube life by driving them at low contrast. You have plenty of other objectives.
If an impressive picture is one of them then tube wear is the price to pay. If you don't focus on at least one priority (torus or large or 3D or blend)
then you might end up in totally dropping the project and having nothing.

In order to get the same light output I'd rather run a single projector hard than a stack in idle.
Total installations lifetime will probably be the same as tube wear is not the only problem that can occur in the next years.
(Competition from cheaper and better digital projectors beeing only one threat)

My tubes are blooming ince 3000 h and when they are through I just put in the next ones.

Cheers rumpeli


Quote:
* Blending by itself is a huge challenge.
* A torus is a big challenge, and I'm not sure a torus is compatible with blending. A torus needs a high-gain screen to focus the light.
I think blending really requires a unity-gain screen, or else you get different reflectivity from the two projectors.
* 3D is a bit of a challenge.


I will tell you all a secret. I know that this would be a long way to go and my first (hopefully working) setup will be a single 8500 on the floor or table
with torus and Nvidia glasses. Maybe i will buy other glasses, but these are there and i'll try them.
If this works, i will try blending. If the blend works on the floor, i'll hang them both up on the ceiling and try again.
But i don't want to build several screens. One screen at the start, that is intended to work on a blend and bright enough
for 3.12m wide shutter 3D.
Do you get the idea?


Brightness calculation:

Quote:
No problem with your math, problem is you data! The 1200 Lumen rating is either A)misleading or B) just stupid.
That rating usually comes from a 10% white window. I don't know about you, but I watch movies not 10% white windows.
On a movie, a 9" PJ on a 16:9 screen will deliver under 200 lumens on a high APL scene.
On a 50% APL scene they can deliver a bit over 250 or so.


Don't know what he means by APL, but if you calculate it with 200lumens, usning my screen size of 10.24ft by 5.74ft,
you'll get 3.45ftL. Using two projectors, it's double.
6,89ftL. Too much? I don't think so. Use a gain 3 surface screen and you'll get 20,7ftL.
That seems about right for 3D.
Just numbers and those are even not measured (the 200lumens e.g.) but estimated.

do we have a calculation master who knows real lumen numbers?

I like the idea, Athanasios draw. So every projector has its own torus. Apparently.
Should not be a problem for the lenses and scheimflug wouldn't be stretched too much
(like if 2 projectors were parallel to each other).

Rumpeli: Is this projector of yours a marquee? If so, afaik marquees bloom all the time.
Frankenyokes should help there.

I read about a hard torus screen somewhere, i do like the idea much more then buying fabric
and use the vacuum fan method for the torus.

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garyfritz



Joined: 08 Apr 2006
Posts: 10670
Location: Fort Collins, CO


PostLink    Posted: Tue May 27, 2014 7:50 pm    Post subject: Reply with quote

tschaeikaei wrote:
Quote:
No problem with your math, problem is you data! The 1200 Lumen rating is either A)misleading or B) just stupid.
That rating usually comes from a 10% white window. I don't know about you, but I watch movies not 10% white windows.
On a movie, a 9" PJ on a 16:9 screen will deliver under 200 lumens on a high APL scene.
On a 50% APL scene they can deliver a bit over 250 or so.

Don't know what he means by APL, but if you calculate it with 200lumens, usning my screen size of 10.24ft by 5.74ft,
you'll get 3.45ftL. Using two projectors, it's double.
6,89ftL. Too much? I don't think so. Use a gain 3 surface screen and you'll get 20,7ftL.
That seems about right for 3D.
Just numbers and those are even not measured (the 200lumens e.g.) but estimated.

do we have a calculation master who knows real lumen numbers?

Yes we do, yer just not listening to him. Laughing Laughing

APL = Average Picture Level. A full-white screen is 100% APL, full-black is 0% APL, most content is in the middle. http://journal.smpte.org/content/76/9/924.full.pdf says most TV programming runs around 40-50%. Full-snow scenes like Ice Age run higher, shadow-detail scenes that CRT fanatics love run lower.

Why does that matter? The CRT has a limited amount of current. Big bright pictures ==> lots of photons from the tube ==> lots of electrons hitting the phosphor ==> lots of current generating the electrons. So lots of bright area takes lots of current. If you try to display a full-screen bright image, the CRT runs out of current, and you end up with a darker image than you should.

This is the difference between ANSI lumens and "Peak" lumens. Peak lumens measures the brightness of a full-100%-white area that only covers 10% of the tube face & thus the screen. Since it's only 10% of the screen area, it doesn't hit the current limit, so you get the full brightness the CRT is capable of (at that contrast level). Start expanding the 100%-white area, and at some point the CRT will hit its current limit, and the 100%-white area will start to get dimmer. By the time you fill the tube face / screen with the 100%-white area, you are stretching that limited current across a much bigger area, so it's much dimmer than when you only lit up 10% of the screen.

The "light up 10% of the screen with 100%-white" brightness is Peak lumens. The "light up the entire screen with 100%-white" brightness is ANSI lumens. The 8500 is rated 1200 peak lumens; it's that bright if you just light up a small area. Light up the whole screen with 100%-white and you will only get 225 lumens. (The 8500 is rated 225 ANSI lumens.) Full-screen 100%-white is 255/1200 = roughly 1/5 as bright as 10%-at-100%-white.

Do the same thing with a digital projector and the lumens will be the same when 10% or 100% of the screen is lit. Digital ANSI lumens == peak lumens. (Which is why digital projectors don't even talk about peak lumens. It's just a CRT-marketing term.)

Given SMTE says typical program content is about 50% APL, it doesn't take as much current as full 100%-white. Dave said a CRT could generate 250 lumens on 50% APL. I suspect he's pessimistic on that figure. If the 8500 can light 10% of the screen at 1200 lumens and 100% of the screen at 225 lumens, then I'd bet you could light the whole screen at a level somewhere in the middle -- say, 700 lumens or so. (In reality it's probably higher.) But it WILL look a bit dim when you're looking at a full-screen snow image.

So: unless you're really worried about how full-white scenes like Ice Age look, you don't have to assume the ANSI lumen figure. I'd guess 500-700 lumens is a safe estimate for normal image content. So you might get your desired brightness level with only one projector and a torus.
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hansilili



Joined: 09 Mar 2007
Posts: 302
Location: Köln, Germany


PostLink    Posted: Wed May 28, 2014 12:39 pm    Post subject: Reply with quote

A couple of years ago I had mail contact with theis company www.silverfabric3D.de . They sent me a DIN A3 sample of their perforated aluminium coloured fabric.
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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Wed May 28, 2014 2:05 pm    Post subject: Reply with quote

Yes, Gary. Everything you write is right, but not new to me. I was just looking for one number.
You gave me the ANSI Lumen and thats all i needed. Sorry for being not clear about that.
But your effort is sure not unnecessary.
The last thing you mention is of interest.

Quote:
So: unless you're really worried about how full-white scenes like Ice Age look, you don't have to assume the ANSI lumen figure. I'd guess 500-700 lumens is a safe estimate for normal image content. So you might get your desired brightness level with only one projector and a torus.


Yes. And if i add 3D and loose 60% of the light again, it will work good with two projectors, for the light is doubled again.
Lets say we have about 80% of the initial brightness (one projector, torus high gain-screen) again.
Doesn't that fit in my plans?

Let's talk about screen material again. I read something about "hard torus" (with a hard surface), that doesn't force me to buy expensive fabric (i could paint a hard surface) and the fan would be unnecessary.
I have to place the screen immediately in front of a wall and the fan would be a problem.
My living room door is 20cm from the screen and if the screen gets to deep (or with space to the wall), we would easily bump the screen when entering the living room.

Regards, Julian

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garyfritz



Joined: 08 Apr 2006
Posts: 10670
Location: Fort Collins, CO


PostLink    Posted: Wed May 28, 2014 4:46 pm    Post subject: Reply with quote

3D and two projectors might work. But if the 8500 is bad for stacking, you'd have to blend, and you don't double the lumens then. You're back to each projector projecting about 1.95m wide. The light benefit comes from each projector only projecting half the image, instead of a single projector covering the whole large image (and using a smaller amount of tube face).

Hard torus screens are possible, but I don't know how you make them. I suspect it would be a much bigger project than making a fan-tensioned fabric torus.
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tschaeikaei



Joined: 08 Apr 2013
Posts: 473
Location: Germany/Saarland


PostLink    Posted: Wed May 28, 2014 6:18 pm    Post subject: Reply with quote

Lets say i have more light with a blend than with a single projector on the same screen.
The problem about the soft torus with fabric is that fabric (especially high gain fabric)
is expensive.
I searched on some sites, and all i get is about 60€ per m² ( about 7,4USD per square foot).
Thats about 330€ or 450USD. Too much.

I have to find a cheaper way. Hard paintable surface and aluminium spray (bright silver) or zinc spray (dark silver).
Have to try that.

It would be hard for me to build a "soft torus", because the depth of the whole screen (with the frame and fan).
It would stick out to much into the room so we bump it each time entering the living room.

Regards, Julian

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small Teufel 5.1 Audio | HTPC | Pioneer HPM 100
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Nashou66



Joined: 12 Jan 2007
Posts: 16170
Location: West Seneca NY


PostLink    Posted: Wed May 28, 2014 6:20 pm    Post subject: Reply with quote

That is actually a really good price!!! Considering real screen material like stewart screens are 10 times as much.

nashou

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