Building a Box Around a DIY Screen - AVS Forum
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post #1 of 27 Old 04-23-2011, 07:11 PM - Thread Starter
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Building a box around a DIY screen doesn't seem to get mentioned much, and so I offer this thread.

Problem:
With the projector on, light bounces around the room and back to the screen which washes out the projected image. This effect can be mild to severe depending on various factors. Usual discussions regarding solutions for this problem often revolve around DIY screen solutions, masking the border of the screen, painting walls and ceiling, dimming the lights, and blocking light from windows.

Another Solution:
Build a box similar to an entertainment cabinet that sticks out around the DIY screen, and apply black velvet to its interior. Such a box should be at least 9" deep, 12" is better, and no more than 15" is likely to be needed.

The idea with this is to minimize the incident of ambient and reflected light from reaching the screen - and thereby gain a better picture.

A simple example demonstrating the effect gained by such a box:
Go outdoors in the daytime and shade your eyes with your hands so as to block light above and the outer sides of your eyes. Lifeguards are commonly known to do this. The result is you can better see what ever you're looking at.
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post #2 of 27 Old 04-23-2011, 07:55 PM
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IMHO:

One of the big advantages of a projector is the fact that you can hang a very slim screen on the wall to save space. I don't see a huge box being a viable solution for many people, and to me it'd be just hideous to have that contraption hanging on the wall.

A velvet border makes a DYI screen look really professional, and a home theater doesn't feel like a theater at all if it's not painted in dark colors. Window treatments are pretty simple to implement and have the added benefit of helping with acoustics.

Budget Home Theater:
Denon AVR-1911 Receiver, Bic V-1220 Subwoofer, Micca MB42/C Speakers, Epson 8350 Projector, Home-made ~90" 16:9 Screen, Berkline 13175
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post #3 of 27 Old 04-23-2011, 08:37 PM - Thread Starter
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Right, it certainly could be made to look like a hideous contraption... LOL.

There's no doubt about it - a balance would need to be struck between form and function. While painted black boards mounted to the wall may work, most might prefer a more elaborate construction, like something resembling an entertainment center - essentially a big box on top of a foundation.

But the principle involved remains sound. Build a box with a velvet interior, and get a better picture.
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post #4 of 27 Old 04-23-2011, 08:53 PM
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You can build out your screen wall pacing the speaker behind acoustic transparent black fabric and making the area where the screen is an alcove (in a box) that is recessed in the wall and looks very nice and clean.. check out the theater room forums for lots of examples.
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post #5 of 27 Old 04-23-2011, 09:25 PM - Thread Starter
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Very nice contribution - thank you. This option seems to be gaining in popularity among those building their HT.

As an aside, I consider it a valuable practice to consider the audio along with the video for any HT, whether the screen is acoustically transparent or not.

Quote:
Originally Posted by airscapes View Post

You can build out your screen wall pacing the speaker behind acoustic transparent black fabric and making the area where the screen is an alcove (in a box) that is recessed in the wall and looks very nice and clean.. check out the theater room forums for lots of examples.

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post #6 of 27 Old 04-23-2011, 11:30 PM
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I thought about something a little more descreet.
Why not splitting the screen in an upper and a lower half and installing only two covers which can be fold up, resp. fold down to 90° (similar to fronts of horizontal boxes many of use in their living room).

With such an installation one could cover the inside (when closed) with velvet
and upgrade the outside with the used wall-colour (quasi to hide the screen) or e.g. use a pic of the partner (and upscale it with a software like rasterbator) or many more....

+ more or less descreet solution
+ a lot of features for designing (in closed status)

- no covering on the vertical sides

What do you think about it ? ... I´m allready brainstorming for months but still sticking in the phase of renovating the room.
Richie

PS: Please excuse my pure english. I hope you were able to follow my descriptions anyway.
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post #7 of 27 Old 04-25-2011, 01:32 PM
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Quote:
Originally Posted by airscapes View Post
...and making the area where the screen is an alcove (in a box) that is recessed in the wall and looks very nice and clean.. check out the theater room forums for lots of examples.
This pic always comes to mind when I think of a shadow box type setup. Not a DIY screen, but the enclosure is there for the same purpose.

Pulled from the 'Show us your screen walls' thread:
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post #8 of 27 Old 11-16-2011, 09:42 PM - Thread Starter
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That's a good description of it, a shadow box. Custom made, however you like it.
Quote:
Originally Posted by HDvids4all View Post

This pic always comes to mind when I think of a shadow box type setup.

There are a variety of solutions from simple to elaborate. A simple one for a wall mounted screen would be this. Mount 2 or more hinged rods along the top of the screen. The rods swing out pointing forward. Then drape black material over the rods making a 3 sided shadow box. Velcro on the rods and material could be used to help secure the material.
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post #9 of 27 Old 11-17-2011, 07:09 AM
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The dark box around the screen can also be the room. In a perfect world my media room would be much like what I show here in a dark screen wall and side walls and ceiling about 5 ft. from the screen. I wasn’t able to do the left wall but would have loved it if I had total control over the room design to build the black cave with screen inset. The advantage is clearly shown in the second photo with a bright end of the room where the viewer’s sit. Ambient dilution of CR is greatly diminished this way and it allows for a much brighter viewer friendly seating end.





Bud

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post #10 of 27 Old 11-18-2011, 08:30 PM
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BTW...the Box shown is 15" deep. Screen is inset approx 6" from the sides and 8" from the Top & Bottom

Even with this effect in use, the advantage obtained by reducing the tendency of "sideways" reflected Screen light output onto side walls being greatly reduced is /can be mitigated (offset) by the casting of a shadow onto the screen by any source of ambient light is forward & above or to either side pf the box.

While any screen so made as to have ambient light resistant ability can...and will offset the presence of such, if a darker shadow is cast across the screen by the edges of the Box's perimeter blocking such incoming light, there will be a noticeable shadow...or "Terminator" edge, either Horizontally or Vertically oriented (..or both dependent upon light sources).

This same effect is also plainly seen when a Screen's Trim has too high an inside edge (3/4" can do it...) and one can see a dark line against / out from the edge of the trim. If light cannot each the screen due to an obstruction,.....you will ave a darker area.

Essentially so, the "Box" is not to be considered as being a good example of restricting intrusive ambient light coming from outside the screen's perimeter, but rather simply a method of restricting "side-ways reflected Screen light" from hitting closely adjacent wall / ceiling surfaces.

Even so....it's appearance is still worth the effort, and the performance gains to be had as far as minimizing light scatter onto walls make any such project worthy of consideration. In the case shown, the close proximity of the sloping sides of the ceilings (...which could not be painted due to WAF issues...) had to be protected from the screen's light output.

To quote James T. Kirk;
"I'm laughing at the superior intellect"

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post #11 of 27 Old 11-18-2011, 08:35 PM - Thread Starter
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I instead would have wanted a larger screen inside that shadow box, movable black panels to crop the screen for different aspect ratios, the front of the room painted black, and much better options for incorporating front speakers (which I won't go into in the screen forum).

Hopefully this thread will continue to promote a variety of beneficial options.
LL
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post #12 of 27 Old 11-18-2011, 08:49 PM
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The larger the screen...the closer the the edges are to the sides...the less effective the reduction of the reflected light is...(...the sides of the "Box" will be illuminated...) and the less of a "Floating Screen" effect is had. Also, the "Shadow" effect will be all the more noticeable.

And just as well...., the closer the top edge of the screen is to the top "inside' of any such deep box, the more "lower" the Projector's position must be to allow the edge of the projected cone of light to pass unobstructed. For many that would mean having a much too low a "Drop" for the PJ.

There are more things to be considered when building such a box than simply insetting a screen into such an affair. Basically speaking, (...and meaning no disrespect...) until you actually do one of the things within such a deep enclosure, your not going to realize what will...and will not work effectively.

And you can be certain of this...any such enclosure less than 15" deep will not effectively do much of what one might hope for.

As far as beneficial options that are purposefully directed toward achieving the goal as suggested by the Title of this Thread, if one does not in the least meet the minimum criteria as shown in the example above....it ain't a'gonna happen. Certainly you can greatly reduce light scatter as mentioned (...the initial "Box" with the inset Stewart Screen can accomplish that....) but if that means you must drastically restrict incoming light to avoid the "Shadow", than where is the real advantage beyond achieving the reduction of such light scatter?

To quote James T. Kirk;
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post #13 of 27 Old 11-18-2011, 08:54 PM - Thread Starter
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Lots of audio / video factors to consider, making it fairly easy to not get optimal results or even screw up. So hopefully those considering this will be encouraged to post for help.
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post #14 of 27 Old 11-18-2011, 09:04 PM
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Well that's the intent of my post. It's rare indeed when anyone can manage to take to account every variable, let alone even be aware of such. The ability to help other avoid the pitfalls of seeing something they gotta have / try, but not knowing all the "ins & outs' of what can and cannot be expected is exactly what I and others like yourself can and do offer the uninitiated the help and advice they need.

I answer the number of posts I do because I want to proffer to such posters the experience of having "been there...done that" and help such others learn from a few of my own mistakes....and more importantly, the end results of my successes.

To quote James T. Kirk;
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post #15 of 27 Old 07-27-2012, 07:31 PM
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Quote:
There are a variety of solutions from simple to elaborate. A simple one for a wall mounted screen would be this. Mount 2 or more hinged rods along the top of the screen. The rods swing out pointing forward. Then drape black material over the rods making a 3 sided shadow box. Velcro on the rods and material could be used to help secure the material.

That sounds like a nice, simple, great idea. Did you or anyone try it? It would be a good deal of material... 48" x 233" nominally to cover the 3 sides. That's like 7 yards... or ~$220 of Fidelio Velvet!

I'm wondering if this solution + a retro-reflective screen would help my poor black levels (in a bright scene with a little bit of dark content, my contrast ratio is 3:1... yes you read that right!).
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post #16 of 27 Old 07-27-2012, 07:57 PM - Thread Starter
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Quote:
Originally Posted by sarangiman View Post

That sounds like a nice, simple, great idea. Did you or anyone try it? It would be a good deal of material... 48" x 233" nominally to cover the 3 sides. That's like 7 yards... or ~$220 of Fidelio Velvet!
I'm wondering if this solution + a retro-reflective screen would help my poor black levels (in a bright scene with a little bit of dark content, my contrast ratio is 3:1... yes you read that right!).

A shadow box would deal with ambient light, direct and reflected. So you would notice a bigger improvement in picture quality with a worse ambient light problem than you would with a lesser one.

$200 worth of velvet would be nice. When I wrote that I was thinking more in terms of simple and inexpensive, like a cheaper black material. I never made a 3 sided shadow box for a DIY screen. I only suggested it as a simple solution. I did however make a 3 sided shadow box for my computer monitor once that simply consisted of black construction paper and tape. And it worked well.

smile.gif
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post #17 of 27 Old 07-27-2012, 08:13 PM
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I really am thinking of just getting two 48" rods, mounting them on the upper two sides of the screen, then draping 45" wide, 8 yards long black triple velvet (syfabrics.com, reflectivity of 0.6%) around the top & sides of my screen. Velcro seems like a good way to keep it in place, as you suggested, otherwise the top would sag. I guess it wouldn't be the prettiest solution but it'd probably dramatically help my contrast. Right now, it's just unwatchable.

But with a High Contrast High Power screen, it's possible I won't even need this at all...?

What worries me more is the wall of mirrors I have 25' in front of my screen... not sure if that's also contributing to my loss in contrast!
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post #18 of 27 Old 07-28-2012, 03:02 AM - Thread Starter
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Quote:
Originally Posted by sarangiman View Post

I really am thinking of just getting two 48" decorative wall brackets, mounting them on the upper two sides of the screen, then draping 45" wide, 8 yards long black triple velvet (syfabrics.com, reflectivity of 0.6%) around the top & sides of my screen. Velcro seems like a good way to keep it in place, as you suggested, otherwise the top would sag. I guess it wouldn't be the prettiest solution but it'd probably dramatically help my contrast. Right now, it's just unwatchable.
But with a High Contrast High Power screen, it's possible I won't even need this at all...?
What worries me more is the wall of mirrors I have 25' in front of my screen... not sure if that's also contributing to my loss in contrast!

To make it nicer looking, you could fashion some sort of facing (border) along the top and perhaps the 2 sides. Something like styrofoam wrapped in velvet may do. Reinforce the styrofoam if needed. Affix with velcro or hooks. Simple stuff. A border is often made similar to this when mounting a screen to a wall.

I owned a Hi-Power screen for a while. It has a great initial "wow effect", but I would not recommend it except in limited circumstances. It sends a lot of light back toward the projector (and rear wall). But after a short while I didn't like its results.

Your projected image is no doubt getting washed out by ambient light hitting the screen. There could be light reflected back to the screen off the ceiling, floor, sides, rear mirrors, furnishings.

The 3 sided shadow box you propose would help with light hitting the screen from the top and sides, but would not help with light reflecting from the mirrors to the screen. You'd need something between the mirrors and screen to reduce this. I suggest being prepared to deal with this in case the picture quality is still not up to speed after using the shadow box.
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post #19 of 27 Old 07-28-2012, 03:06 AM - Thread Starter
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I may have misread your last post. If the mirrors are on the same wall as the screen, then it won't factor into the problem of ambient light hitting the screen nearly as much. And so the 3 sided shadow box would then help much greater than if the mirrors were on the wall facing the screen (rear wall).
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post #20 of 27 Old 07-29-2012, 02:24 PM
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No you read that right. The mirrors are on the rear wall, 25' from the projection screen. I will do a contrast measurement with the mirrors covered by curtains later tonight.

The 'shadow box' thing is harder than I thought. I got some piping that I can extend out ~40" from the upper corners of the screen, but this is actually a significant amount... I think it'll just look ugly. It also won't deal with the reflections off my floor, and other reflections beyond the 3.5ft that won't be blocked by the velvet:



Hence I'm thinking the Da-Lite HCHP or HP or the 'Contrast Radiant CH2700E from Draper (http://lib.store.yahoo.net/lib/focusedtechnology/contrast-radiant-ch2700e.pdf), the latter having a 30º viewing cone, with a half-gain angle of 15º. Not sure if Da-Lite's numbers of 30º & 20º for HP & HCHP, respectively, are viewing cones or half-angles, so not sure how that compares. Regardless, w/ a retro-reflective screen, since most light will be sent back to the projector & rear wall, I'll likely have to cover the mirrors.

But isn't a shadow box unnecessary w/ a retro-reflective/high-gain screen? I'm assuming b/c of the narrowing viewing cone, most light will not be scattered to wall/ceilings nearby (though perhaps to walls/ceilings further away, where a shadow box won't help).
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post #21 of 27 Old 07-29-2012, 04:29 PM
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I'm baaaaack........eek.gif

sarangiman, in your case, the extremely close proximity of the ceiling to the top edge of the screen's viewable area is your real deal breaker. The Right sidewall comes in a close second...the Floor a distant 3rd.

As a fact, the HP HC screen is a real start, but consider that even a with a half-gain angle of 15º, when your viewing 16:9 bright content, both the closest surface will still flood the room with light. And while such reflected and returning light will be mitigated by a Retro-Reflective screens performance, especially on which is also a "High Contrast" Gray in shade, when the angle and proximity of such light is so extremely close, the brighter the content, the more pronounced the difference will appear on such a screen. You will see a more pronounced effect along the edges, with the more centralized areas retaining image quality. In order for you to achieve a true elimination of light scatter, your gain on the screen would have to approach 5.0-6.0+ (..and really REALLY be within those numbers....). The big nasty of going that direction is the absolute certainty of seeing graininess and screen artifacts. When one combines high Gain with a Darker surface, the brighter areas within such a screen's surface will always stand out when your viewing at a close enough proximity that you can resolve the individual reflective elements that are needed / used to effect such gain.

No......you need to in at least some manner a way to reduce your surface reflections. If you combine the use of a less reflective covering AND Retro-reflectivity, then you will have gone the distance required for not just noticeable, but significant improvement.

A within reason solution "screen-wise" that garners at least 2.0 actual gain, combined with a darker but attractive material (...it need not be actually Black...) would be effective enough by my reasoning. 24" out from the Screen wall on the Ceiling and right Sidewall would also be sufficient, far better than naught, but less "in your face" during non-viewing periods.

Be advised that without completely changing your Room's color scheme, you can't get rid of all your reflective bugaboos. But also be advised that by doing at least the minimum described just above, you will effect a greatly improved condition in which to enjoy your content.

Oh yeah...the Floor. Get a Throw Rug, or better still, an appropriately colored Carpet Remnant and have it trimmed/edged to create a 48" x 110" or so cover for the floor below the screen. Would that everything else you need to consider doing be that simple.... rolleyes.gif

Now addressing the Mirrored rear wall.......in reality it will only be an issue in the rear of the room, and even then, between the lessor intensity of the light that has to travel that far to reach the mirrors, and the further attenuation such light will receive as it's collected and reflected off those Mirrors, you can probably reduce their impact by 95% simply by covering them with an attractive, semi-translucent, almost "Gauze-like" Curtain treatment.

To quote James T. Kirk;
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post #22 of 27 Old 07-29-2012, 04:50 PM
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Thanks MississippiMan. You're right, w/ a 30º cone, bright areas at the top of 16x9 content will still illuminate the ceiling.

You can see the ceiling/walls lit up even w/ a HP screen here:
http://www.youtube.com/watch?v=p0hP079-mns&feature=related

So I guess I'll have to put those pipes up & get that velvet... and deal with the mirror.

I'm still having this debate over pulldown vs. fixed frame. One thing that has me worried is Da-Lite's system for creating tension w/ the HP screens. The Da-Lite fixed frame (Cinema Contour) w/ HP seems to apply tension by using brackets mounted to the wall to push down on the bottom of the screen material. I.e. it's the position of the 'HP brackets' on the wall that creates tension on the screen... hard to explain, video here: http://www.youtube.com/watch?v=ZCXSEtURRtk

That seems difficult & slightly stupid.

Draper's method using the notches seems much easier: https://www.audiogeneral.com/Draper/onyx_instructions.pdf

Wondering if I should just go with the pulldown at less than half the price!
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post #23 of 27 Old 07-29-2012, 05:07 PM
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Actually, a little trigonometry shows us that w/ a 30º viewing cone, or 15º half angle, with the top edge of my screen 5" below the ceiling, serious reflections from the top edge of the screen will start at 18.7" (Tan 15º = 5"/x, solve for x)... of course there'll be reflections before then since the screen is still reflecting/scattering at those angles, just with lower gain. So yeah maybe 2ft will help w/ bright reflections at the edge of the screen... more would probably be better.

Only one way to find out smile.gif
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post #24 of 27 Old 07-30-2012, 02:01 PM
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sarangiman,

Re-evaluate your photo above.

You'll see that even with several inches of the top of Screen under "mask" due to no content, the inside corner of the juncture of Screen Wall / Ceiling is insanely lit.

Trig be damned! We got sumpthin' "Quantum" goin' on! eek.gif

As shown, the really only dark area anywhere is the wall space between the top of the Screen and the Ceiling.
(...thank goodness we are not troubled with gravitational lensing or light warp-age....)

The cold, hard facts are....if you fudge on any aspect of the room / screen / PJ co-adhesiveness needed to obtain the highest level of performance, there will be a respective loss of performance commensurate to the degree of importance of the neglected or omitted item.

So choose wisely.

(hint: Paint the ceiling and wall appropriate colors and by Golly Gee whiz....you won't even need an expensive Screen. Take all those savings and your Wife and GYAs to Maui! )

To quote James T. Kirk;
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post #25 of 27 Old 07-30-2012, 02:12 PM
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Quote:
You'll see that even with several inches of the top of Screen under "mask" due to no content, the inside corner of the juncture of Screen Wall / Ceiling is insanely lit.

That's b/c this is the Elite 1.1 gain screen with a diffuse surface that scatters light everywhere. My trigonometry calculation was for a retro-reflective screen, one w/ a half-angle of 15º. So, for example, for the Draper CH2700E 'Contrast Radiant', 18.7" in front of the screen on the ceiling will be where content at the top of the screen will be reflected w/ a gain of 1.25.

For a diffuse surface that scatters light, this calculation is completely invalid. Light can be scattered at any angle from a diffuse surface, so it's not at all surprising that the ceiling is lit where it meets the wall.

But I doubt this'll be the case once I put up a retro-reflective screen... of course there'll be some light reaching there since gain doesn't drop to 0 at any angle (well besides 180º).
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post #26 of 27 Old 07-31-2012, 06:01 AM
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Originally Posted by sarangiman View Post

That's b/c this is the Elite 1.1 gain screen with a diffuse surface that scatters light everywhere. My trigonometry calculation was for a retro-reflective screen, one w/ a half-angle of 15º. So, for example, for the Draper CH2700E 'Contrast Radiant', 18.7" in front of the screen on the ceiling will be where content at the top of the screen will be reflected w/ a gain of 1.25.
For a diffuse surface that scatters light, this calculation is completely invalid. Light can be scattered at any angle from a diffuse surface, so it's not at all surprising that the ceiling is lit where it meets the wall.
But I doubt this'll be the case once I put up a retro-reflective screen... of course there'll be some light reaching there since gain doesn't drop to 0 at any angle (well besides 180º).

I think that is a huge ask for any screen in the set up and tight clearances shown. You might be able to pull it off, but I can't imagine what you might have to sacrifice to avoid all the light splatter. I'll be very interested to see how it works out so please keep posting. I ended up painting a 3 foot wide dark maroon border around the ceiling and it helped, but it still doesn't come close to eating up all the light I am shooting at the screen to get the "pop" I want. Granted my set-up is much power budget, but I think the principles are the same. Hope you are able to fashion a solid solution that will help us all.
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post #27 of 27 Old 07-31-2012, 12:44 PM
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johngraz: Yes, it's a stretch to have this large screen in this small space with these colored ceilings/walls/floors. But I bet it can be set up to somewhat reasonable standards.

I really need to start my own new thread about this b/c I have volumes of data I'd like to present, but to start off:

With the Elite 1.1 matte white screen & an Epson 8350, here are the best (dark scene w/ a few highlights) & worst (bright scene w/ a few blacks) contrast ratios I get:

Best: 1018:1 (slightly inaccurate b/c we're approaching/exceeding the acceptable dynamic range of my 5D Mark III here *cough* Canon *cough cough* too bad I don't have Nikon... so I'll redo this w/ multiple exposures to confirm... i.e. my measured black in this experiment had a SNR of 2... so that could be slightly inaccurate!)
Worst: 14:1

That means my contrast drops almost 100x due to scattered light in bright scenes! It's that bad. I'll show my methodology for this test in my own thread, b/c it gets lengthy.

I've concluded some preliminary tests w/ the HP & HCHP screens from Da-Lite.

They basically show that with all the scattered light from the Elite screen for a completely white scene with a small black rectangle over the patches (6"x6") of HP & HCHP material I have taped to the Elite screen, I still get better contrast w/ the high power screens:

Contrasts:
HP: 34.7:1
HCHP: 39.4:1
Elite 1.1: 15.4:1

All images were taken 18" off projector lens axis (to simulate normal viewing), and patches are at the same level as projector lens, though 18" off center of projector beam (so they could perform slightly better, potentially, but I'm measuring a 2.9 gain, compared to Elite screen, for the HP with this setup, & 2.7 for HCHP, so I think we're fine.)

This basically shows that the HP & HCHP are considerably better at rejecting scattered (off-axis) light. No surprise there. The HCHP seems better than the HP in this regard.

Of course, things will be better if the whole screen were HP or HCHP, b/c there'd be much less scattered light to begin with. So... in a nutshell... progress!

FYI maximum contrast I get with these screens:

HP: 1466:1
HCHP: 1450:1

... both these numbers are better than the maximum contrast I get with the Elite screen (~1000:1), and these measurements were done in the absence of scattered light (b/c essentially I quantitated a small white box on a black background, so there was very little scatter to begin with). I need to repeat the Elite screen measurement though b/c of the dynamic range limitation of my camera, as I mentioned earlier (I used multiple exposures to get the HP/HCHP numbers, so those should be more reliable).

Apologies that this is a little/lot scattered... amidst the experimentation right now so it's hard to write this out in an organized format until I'm finished. But thought I'd throw it out there in any case.

I'll be curious to see how these numbers changed with the 'shadow box'!

Cheers.

P.S. Dynamic iris was off for all measurements.
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