Film-Tech Forum ARCHIVE: REALLY high gain screen

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Posted by Michael Rourke (Member # 1142) on 02-13-2003, 01:34 PM:

I was at the Consumer Electronics Show (CES)in January and there was a display for digital projectors for home theaters and they were projecting onto these screens that were coated with a reflective paint with aluminum flakes in it. The picture was so bright it would allow for viewing in a bright room. I even walked about 50 feet away from this screen that was only about 6' by 4' and it still looked great and I could easily read the credits of the movie they were showing, I wonder if they could be used in our application, or if it was only good with a pixilated image (DLP), they weren't made with holes in them either which would have to be done so the speakers can be behind the screen. Anyway upon seeing this I wanted to go grind up some soda cans and repaint the drive in screen in my town. I failed to ask if these screens could be cleaned if they were to get something spit or hurled upon them, and I assume that water would be very bad for them which would rule out any permanent outdoor setup.

Does anyone have anymore information on these? Maybe have one in their home theater?

Posted by Paul G. Thompson (Member # 655) on 02-13-2003, 01:44 PM:

What did the picture look like when it was viewed at a sharp angle - say about 45 degrees off center??

There is several advertizement screens that are extremely bright, also. Too bright, in fact. One of those are in the southbound lanes of I-5 one mile from the "Executive washrooms" in the northbound lanes north of Tacoma. I think it was LED's and about 1/2 mile away, the resolution looked better than some drive-in theatre screens. The picture was beautiful! And, I might add this: they were moving scenes such as dancing beer bottles, horseback riding in the country, you name it. Furthermore, the picture did not "fall apart" as the sign was approached.

It looks like the maintenance is very high to keep it running. More often that not, there is a block of lights in that picture that seem to be stuck on one color. Two things come to mind:

(1) That sign must be an electronic masterpiece, and (2) It must really suck the electrical power. If someone told me that sign sucked 3 megawatts of power over a 24 hour period, it would not surprise me.

Even the big ones in Las Vegas would not hold a candle to this one for picture clarity and brightness.

I understand the WADOT tried to get the owners to dim it down a little, as it was a major distraction to the drivers on the freeway, and apparently it has caused some wrecks. On rainy nights when the rain falls like cats and dogs, the reflection on the pavement is so strong you can't see where the hell you are going.

Greg and Jack, you know which one I am talking about. Just exactly, what is that thing? [eyes]

Posted by Michael Rourke (Member # 1142) on 02-13-2003, 02:02 PM:

It looked fine at an angle, it was a curved screen and it was sharply focused all the way across. I'm pretty sure it was an American company that made the screen, but the booth was for the digital projector company based in Korea.

Posted by Paul G. Thompson (Member # 655) on 02-13-2003, 02:26 PM:

Cool! I wonder how long it will last.

Posted by John Pytlak (Member # 331) on 02-13-2003, 04:10 PM:

A very high gain aluminized surface, when properly curved, can be very efficient, allowing high image light levels while rejecting stray light. But even with curving, the screen is quite directional. Kodak once sold a solid aluminized screen for A/V applications known as the "Ektalite" screen. Its size was limited to about 50 x 50 inches since it was a solid material curved in a compound curve to optimize the reflection pattern.

Posted by Jack Ondracek (Member # 1466) on 02-13-2003, 05:30 PM:

quote:
from Paul...
Greg and Jack, you know which one I am talking about. Just exactly, what is that thing?

I sure do, Paul... that thing is a blowtorch... and usually too bright at night (still). I also think your observations about the thing would be right on. It's in a really prime location, probably cost a zillion bucks to buy & install, & I wouldn't even want to think about the maintnenance.

One thing that probably indicates the cost as well as anything is the fact that the screen on the other side (facing North) is much smaller, seems to have fewer colors (though that might be a technical issue) and doesn't have the resolution the South screen has.

As for cost... I wonder if the fact that they've been running a lot of "advertise here... call 1-800-XXX..." means something????

Posted by Paul G. Thompson (Member # 655) on 02-13-2003, 06:07 PM:

yeah, just to pay the power bill. [Big Grin]

Posted by Jack Ondracek (Member # 1466) on 02-13-2003, 06:16 PM:

quote:
from Michael R...
...upon seeing this I wanted to go grind up some soda cans and repaint the drive in screen in my town.... and I assume that water would... rule out any permanent outdoor setup.

Michael, there used to be a company by the name of Spatz that made a metallized paint for drive-in screens. However, many drive-ins... and now pretty much all of them (now than Spatz is out of business) just use a good quality flat white latex... though a few have their own "secret formulas". Kelly Moore & Sherwin Williams both have good products, which is basically nothing more than the white tinting base they use.

As for using metalized paint, you'd have to be careful not to put it on a screen that wasn't angled to the booth properly. A lot of drive-in screens are installed straight up & down... and if you have a situation like ours, where the booth has been moved, you could have the screen reflecting too much light at the playground, rather than at the cars where you wanted it.

For the most part though, if a drive-in isn't dealing with a lot of ambient light, it's more often a matter of underlamping, infrequent bulb changes and/or shot reflectors that causes the lousy pictures at some places. There are a lot of 'em out there that are using the original reflector that came with the lamp they used to upgrade from carbon... and if it's not always a matter of the owner just being cheap, it's likely he doesn't know any better... they deteriorate so slowly.

(A lot of 'em get cheap pretty fast though, when you suggest they shell out around 3 grand for a new bulb & reflector! [Cool]

Posted by Stephen Furley (Member # 1277) on 02-14-2003, 03:57 AM:

John wrote:

quote:

Kodak once sold a solid aluminized screen for A/V applications known as the "Ektalite" screen. Its size was limited to about 50 x 50 inches since it was a solid material curved in a compound curve to optimize the reflection pattern.

John, we had a couple of those screens in the late '70s, but we did not find them wery successful. There were three main problems:

1. They were quite expensive.

2. The viewing angle was too narrow for the locations where they were installed, of course, this was not a problem with the screen itself, but with inappropriate use of it.

3. The surface marked very easily, and was difficult to clean. This was a major problem when used in a school, where they tended to get covered in fingerprints, not to mention chewing gum, fish and chip grease, vomit [Eek!]

and just about anything else you can think of, but would probably rather not. [puke]

We also found that they were unneccessarily bright; we used them with the original 3-button Carousel-S projectors with the 150W A1/216 lamp, plus a few of the newer 2-button ones with the 250W A1/233, and both of these gave an over bright image.

This was the era of the halogen lamp, and projectors were much brighter than the old ones had been, so the screen might have been more useful if it had been available ten or twenty years earlier. About the only time we found it really useful was when using the 'epi' part of an ancient Ross eipdiascope, dating from about the '40s, which gave an image so dim you could hardly see it on any other type of screen. The 'dia' part was no longer used, but was made to take the old 3 1/4 inch glass slides, like cinema slide lanterns.

The best use I saw for these screens was on exhibition stands, where there were very high ambient light levels.

Posted by Greg Mueller (Member # 17) on 02-14-2003, 09:15 AM:

Yah, everytime we drive by that "light bulb"(?) screen, we're amazed, and I agree it is an extreme distraction. I wonder if there are any stats on that part of the freeway concerning "crashes while watching tv"? Even with the sun shinning right on it, it is still visable a mile away. I've been checking on it for a few years now wondering when it will begin to die.
So far, so good.
What a successful advertising medium!

Posted by Stephen Furley (Member # 1277) on 02-14-2003, 09:31 AM:

Greg, that sounds like the sort of thing that has been installed, in fairly small sizes, at certain main-line railway stations in London recently. They're so bright that it almost hurts to look at them.

Posted by Paul G. Thompson (Member # 655) on 02-14-2003, 12:41 PM:

Next time I get down that way, I'll see if I can det a digi pic of it along with its specifications. [Smile]

Posted by John Pytlak (Member # 331) on 02-14-2003, 02:07 PM:

Probably similar to Mitsubishi's "Diamond Vision" displays:

http://www.planetanalog.com/pressreleases/bizwire/22637

Not very high resolution or good tone/color scale, but they are BRIGHT!

Here's some others:

http://www.signweb.com/moving/cont/emcrelativityb.htm

Posted by Greg Mueller (Member # 17) on 02-15-2003, 09:30 AM:

Hey (while this topic is current)
I'm going to set up to run some 3D and in all the manuals I've read, they say you must have a Silver Screen for higher gain. The reason being that the polarizing filters both in the lens (side by side anamorphic) and on the audience's eyes will suck a lot of light. The recommendation is for twice the usual illumination.
My questions are
Is the silver screen the best way (cost effective) to increase gain?
Who makes the the highest gain screen?
In my small screening room I'm using a 1kw bulb in a Super Lumex.
Is it safe to set the output of the power supply to higher than rated setting to get more light from the bulb? (Does that work?)
If so how much more?
I'm limited on how much my small power supply will put out so I would have to get both a new bulb AND power supply to get more juice if I went that way.
Suggestions?

Posted by Kenneth Wuepper (Member # 1174) on 02-15-2003, 10:49 AM:

Greg,

The reason for using a metallic screen for 3D is that the surface must reflect the light projected on it and RETAIN the polarization not diffuse it. The matte screens will not work with polarized light 3D.

The fact that there is a gain in light reflectance by using the 'silver screen' is not the major issue here. You should never run the lamp at over the rated current as it is both dangerous and ruinous to the lamp elements. If you are using 2 strip 3D, then there will be more light on the screen by virtue of the two projectors running simultaneously. If you are running side by side or over/under 3D, then there will be a light reduction due to both the optics and the polarizers. Select the light source needed for properly lighting the screen within the ratings of the lamphouse and bulb.

Anaglyph 3D uses the Cyan and Yellow color layers for projection of 3D from a single frame. These are viewed through the Red/Blue glasses. Cyan is the negative of Red and Yellow is the negative of Blue. The Cyan image looks black and white through the Red filter and, similarly the Yellow image looks black through the Blue filter. This system worked fairly well as long as the color layers of the film did not fade too much. (Some patrons with color blindness were unable to view these films in 3D.)

Sorry for the long post but I thought your question was worth the response.

KEN (Don't get your eyes crossed now!)

Posted by Richard Fowler (Member # 893) on 02-15-2003, 10:57 AM:

You will need the silver screen for the light gain but also to prevent the polarized images from becoming depolarized which will "ghost" up the images.
Silver screens for cinema are usually 2.5 to 3 in gain. Vutec, a screen manufacturer for industrial and home markets; produces a solid 10 to 13 gain screen on a rigid parabolic shaped surface which we have used for trade shows. The surface size is limited to a six foot width.
Richard Fowler
Kinoton America Inc.

Posted by Thomas Procyk (Member # 1170) on 02-15-2003, 11:54 AM:

I never quite understood the concept of Silver Screens. I've worked in two locations that had them (one was a former COBB, so their silver screen was 1.85 with no masking [Roll Eyes]

) and in both cases, the results were much like a big-screen TV. Those sitting in the left or right sections would be treated to a dim picture on the opposite side. Those sitting in the middle would see a really bright center, and then a falloff to the sides. True, we never ran any 3D movies, but running regular shows on those screens seemed almost distracting.

When that old COBB was taken over by another company following Regal, they removed the silver screen and replaced it with a matte white one.

The location I work at now has a silver screen, and two lenses in the back of the storage cabinet that say "StereoVision" on them. Assuming these are for the 3D, how would you use them? Is this setup for 3D movies that use the red/blue halo or where there are 2 of the same picture slightly off of each other?

=TMP=

Posted by Jeffry L. Johnson (Member # 453) on 02-15-2003, 12:43 PM:

A silver screen is essential to maintain the polarization of the left and right images of a 3-D motion picture.

Posted by Richard Fowler (Member # 893) on 02-15-2003, 02:45 PM:

Most Stereovision lenses where for projecting over and under widescreen images. The lens barrel has two set of lenses bisected in the center and angled ( actually camera lenses converted for projection use ) and built in polarizers...some StereoVision sets had a 20% magnifier add on optic to increase the image size. The spacing of the upper and lower images varied since there where more than one supplier of 3D optics for production and required that you use the matching projection lens and test film for that spacing ( such as .387 ).StereoVision also supplied an adapter for anamorphic prints with a 1:33 image such as used for House of Wax reissue.
Richard Fowler
Kinoton America Inc.

Posted by Greg Mueller (Member # 17) on 02-15-2003, 07:03 PM:

Ok Silver screen a must. I see Hurley sells a 2.5 gain silver screen with perfs.
This particular film is a side by side anamorphic print. I wonder if the over under lens could just be rotated 90° and used for side by side?
I guess I'll do the screen first and see where I stand

Posted by Richard Fowler (Member # 893) on 02-15-2003, 08:09 PM:

No, the over and under lens is different. The image it is looking at is about 2 perforation high X width while the side by side is 4 perf high x 1/2 image width.
Richard Fowler
Kinoton America Inc.

Posted by John Pytlak (Member # 331) on 02-15-2003, 09:04 PM:

The StereoVision manual:

http://www.film-tech.com/manuals/STEREOVISION3DPRINCIPLES.pdf

Posted by Greg Mueller (Member # 17) on 02-15-2003, 11:25 PM:

Thanks all for the input

Posted by Frank Angel (Member # 248) on 02-16-2003, 03:53 AM:

High gain screens, especially silver screens do have off-axis problems as mentioned, but they do have their place in theatres where the seating does not exceed the screen width by any significant amount. Also, with a silver screen attention must be paid to its angle so hot spots are not created. But when they are installed correctly in spaces where seating placement is ideal, they can be very effective.

I visited a theatre in Kingston NY where the picture was about 45ft wide with an image that looked much brighter than the SMPTE standard 16fl and it was uniform from edge-to-edge; I was struck by the intensity of the image. I was sure he must be burning a 4.5kw - 7kw lamp to get an image that bright and uniform. When the projectionist took me up to the booth, I was expecting to see a big lamphouse and was really amazed to find that he was burning a 1600w bulb in a small 2kw Xetron. I couldn't believe it; how could that picture look so bright? Then he told me that he had a silver screen. I went back into the house and walked to the far isle seats but the brightness remained even from all seats. Just a tad fall off at the very front seats, which you would only expect people to sit in with full houses, and even then this would probably not be noticeable to the average viewer. This was an example of how good a very high gain screen can work in the right situation. Whenever I hear people bad mouth silver screens, I just recount that experience in a theatre up in Kingston NY.

Posted by John Pytlak (Member # 331) on 02-17-2003, 10:05 AM:

Ideally, high gain screens should be properly curved and aimed by ray-tracing. The projector's light should be reflected to a point in the center of the audience seating area. Otherwise, SMPTE Recommended Practice RP95 specifies "Installation of Gain Screens".

One way to check for the proper curvature and angle is to hold a small mirror at various points along the surface of the screen. Hold the mirror to reflect the projector's light to the center of the seating area ("prime seats"). The screen's surface should be parallel to that of the mirror. If not, hold the mirror parallel to the screen's surface -- the mirror reflects the light to the same place most of the screen's light is reflected (hopefully not onto the floor or walls!).

Posted by Andrew Lee (Member # 1330) on 02-17-2003, 01:51 PM:

Most of you are aware about the trade offs and the advantages of using a silver screen. I don't want to make this forum a base for advertising but I thought it may be of interest to explain our new product.

MDI now has a micro-lenticular silver screen available to theatres. This new screen is not only an excellent 3D screen (maintains polarization better than any on the market), it can be utilized for 2D projection as well. The technology behind this product creates a gain distribution which is much flatter than a standard aluminized screen. Hotspotting, and fall-off is drastically reduced thereby allowing the exibitor to present either without worrying about these issues. This screen has undergone evaluation by some of the studios and other cinema technology personnel and has had excellent reviews to date. A lenticular silver screen has been attempted from time to time over the past seventy years, but no one has been successful until now.

Some of you will be seeing this product in your theatres in the near future. If you are curious and attending Showest, stop by and I will be happy to show you a sample.

Posted by Greg Mueller (Member # 17) on 02-17-2003, 02:53 PM:

Tell us more!
What's MDI?
Do you have a website?
Are they "made to order" (size wize) according to customer's requirements?
Are they perfed?

Posted by Andrew Lee (Member # 1330) on 02-17-2003, 04:35 PM:

MDI stands for Marcel Desrochers Inc. We are located in Joliette, Quebec. Over the past 5 years we have manufactured over 10,000 cinema screens, over 200 specialty venue screens (Imax,Megasystems,theme parks,screening rooms,etc), 2000 home cinema screens and 3000 masking motors. Screen frames and masking systems are also manufactured here. It's a small company which has been growing consistantly. MDI had a rough start in the early days but is now coming on strong with quality products and fast delivery. Business is so good right now we are adding another 15,000 square feet to our facility.

The website is MDI

Our website is a little behind as our webpage employee has had an unfortunate illness that has kept him away for some time, but we will be updating soon.

MDI has 4 perforation patterns with 2 more to be added to our production line later this year.

Regards,

Andrew Lee
VP, MDI

Posted by Fred Georges (Member # 505) on 02-17-2003, 07:34 PM:

[Big Grin]

Gregg, Yes, the mirror box attachments CAN be used for side by side 3D. You just have to rotate them 90 degrees and place in front of your anamorphic lens. It's reflection management that you'll find challenging. The mirror box polarizer that has the best range of adjustment would be the Paramount though the easiest to use is the StereoVision.