Film-Tech Forum ARCHIVE: Silver Screen and 3D

This is topic Silver Screen and 3D in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Konen (Member # 41) on 08-17-2005, 11:24 AM:

What would be the benefits, drawbacks of this?

Posted by Gordon McLeod (Member # 33) on 08-17-2005, 12:25 PM:

If you want to do 3d with polarization then there is no option but a silver screen
other advantages
brighter image
more contrast
disadvantages
Hot spot due to gain
poorer viewing angle

Posted by Stephen Furley (Member # 1277) on 08-17-2005, 12:48 PM:

Also, the surface marks easily, and is difficult to clean.

Posted by John Pytlak (Member # 331) on 08-17-2005, 04:00 PM:

High gain screens should be properly curved, ideally using ray tracing, to reflect the light back to the center of the audience. This usually gives the best illumination uniformity.

Posted by Jeff Joseph (Member # 511) on 08-19-2005, 01:11 PM:

To be clear: To run Polaroid 3-D (over/under, side/side, or interlock), you MUST have a silver screen. This is not "optional"; it's mandatory. A non silver screen de-polarizes the light, therefore, no 3-D.

Jeff

Posted by Heath Dutton (Member # 3265) on 08-20-2005, 12:56 PM:

This is my stupid question for the day...

How is a silver screen made? Does it actually contain silver, or is it just colored that way for a higher reflection clarity? Or is there something special in it that prevents the depolarizing?

Posted by Sean Goodrich (Member # 475) on 08-20-2005, 07:00 PM:

Will Silver screens be necessary for digital 3D

Posted by Stephen Furley (Member # 1277) on 08-20-2005, 07:09 PM:

It depends on the technology used; if it relys on different polarisation angles of light to separate the left and right eye images, then yes. There are several other ways of projecting 3-D, but the polarised one is probably the best we have at the moment.

Posted by Dick Vaughan (Member # 540) on 08-22-2005, 08:21 AM:

Those 3d digital sytems that use lcd shutter glasses can use a matt white screen. The demos at Showest and LFCA earlier this year used this system.

Posted by Frank Angel (Member # 248) on 08-25-2005, 08:07 AM:

On the other hand, the LCD system does cut down the light that actually gets to the eye (the lenses in there "opened" state are by no means zero light loss) so the light gain that a silver screen would give in an LCD 3D system wouldn't be a useless throw-away.

The original CinemaScope "Miracle Mirror" screen was a silver surface screen. It was part of the Fox specification for their new system and it was necessary because of the loss of light through the anamorphic lenses. It was a curved silver screen (the curve that John pointed out was also part of the CinemaScope spec and needed as he said to redirect light evenly back to the audience), but besides the curve, the one thing that distinguishes it from today's silver screens and all but eliminated the dreaded "hot spot" that is associated with and has given a bad name to silver screens, was that the Miracle Mirror screen was a lenticular surface as opposed to a purely flat silver surface.

Although I have asked techs at both Harkness and Technicote what the difference is between a lenticular silver and the flat silver screens they use today, I have not ever gotten an explanation that I can understand. I was told that lenticular silver screens are more expensive to produce. But the reason that they are no longer manufactured is because with the advent of high power xenon lamps, there is not enough demand for a very expensive high gain, no hotspot screen when you can use a much cheaper matte screen and just up your lamphouse light output.

Seems to me, if someone were to make a lenticular silver screen, it would be a perfect surface for a venue that wanted to run 3D on occasion but without compromising 2D presentation by introducing hotspots. It would allow either getting more light for standard 2D films or save $$$ by being able to reduce lamp size. Either way, it would be a plus.

Any screen manufacturers reading this?

Posted by Richard Fowler (Member # 893) on 08-25-2005, 08:51 AM:

Hurley has silver lenticular and I think Technikote could produce as well. Based on pricing on Hurley standard silver versus silver lenticular is about 30% more.....heads up on cost concious purchasers....ask and pay, the manufacturers will be happy to supply [Razz]

The lenticular material is usually fabric backed so it is a bear to install [Wink]

Posted by Don Furr (Member # 1469) on 08-25-2005, 08:59 AM:

This discussion takes me back a few years. Some of the theatres we leased back in the early 90's had white screens that had been spray painted silver during the 80's 3D craze. Talking about hot spots and streaking.....had to replace 'em all. The first mistake I made was hiring a crew from Texas to attempt to clean those hand sprayed silver screens. What a disaster [thumbsdown]

Still living and learning.

Don

Posted by Frank Angel (Member # 248) on 08-25-2005, 09:21 AM:

Richard, that's good to know. When I spoke with Technikote they didn't have a lenticular screen, and what they can't sell you, they don't want to talk about. I never spoke to Hurley, but if they are now selling a lenticular, I would be very interested in considering it. I would love to do double projection 3D and get better light from my carbons for regular presentation. I won't be able to get a curve tho. The screen flys.

Posted by Gordon McLeod (Member # 33) on 08-25-2005, 01:10 PM:

Cinemecanica used to make an excellent silver lenticular screen don't know if they still do

Posted by Paul Mayer (Member # 355) on 08-25-2005, 01:58 PM:

Another quality of lenticulars is that they reject off-axis light. Lenticulars are often spec'd for rooms that are difficult to darken sufficiently, like some classrooms or conference rooms. They produce acceptable images in situations where other screen surfaces would wash out.

Posted by Gordon McLeod (Member # 33) on 08-25-2005, 02:21 PM:

There used to be a screen called Protolite that had a lensed style lenticular finish I don't know if it is still around

Posted by Kenneth Wuepper (Member # 1174) on 08-25-2005, 02:52 PM:

Here at the Temple Theatre, the 23 x 46 1/2 foot "CinemaScope" screen was silver lenticular and it was on a wooden frame which flew. That screen was also curved, 26 inches farther from the apron in the center than it was at the ends. The screen was also tied back to match the 23 degree angle from the booth. The frame was attached with stage pegs on the ends and was curved around another stage peg in the center. In later years the silver tarnished and was painted over with matte white. After 49 years of service that screen was replaced.

The current screen is a Hurley "Super Glo" matte white and is stretched on a custom made 2 inch diameter Aluminum pipe frame. This screen also flies. The curve of about 12 inches works as there is no hot spot with this material. We do still draw the top back for reasons of focus and keystone elimination.

KEN

Posted by Richard Fowler (Member # 893) on 08-25-2005, 03:26 PM:

I had a protolite screen for video projector rentals. It had a very high gain which was great for those weak CRT type of projectors. The screen construction was a clear mylar cover, a silver foil sheet and the embossed fabric back bonded together...expensive but after a few years of use the laminated surfaces became unglued.

We are boarded up as hurricane Katrina is planning to visit us very soon [uhoh]

Posted by Mark J. Marshall (Member # 1409) on 08-26-2005, 01:33 AM:

What is meant by a screen "flying"?

Posted by Stephen Furley (Member # 1277) on 08-26-2005, 02:01 AM:

Hoisting the screen frame up into the fly tower above the stage to leave the stage clear for non-film use. If you've got a venue that's used for both film and live shows then you've got to be able to either fly the screen, or if you haven't got the height to do that, you have to use a roller screen. I've seen roller screens up to about 45 feet, they work ok, but the bottom masking can be a problem, it's often just the bottom of the screen painted black, and, of course, they can't be curved. If you've got a fully-equipped stage then the screen is simply suspended from one set of counterbalanced lines, and at the end of a film you can just close the curtains and fly the screen frame in a few seconds, ready for stage use.

Posted by Frank Angel (Member # 248) on 08-26-2005, 04:26 AM:

A fly screen COULD be curved, IF you have the luxury of useing as many pipes on the fly system that it would take. Having to get an arc with the center bowed back 26 inches would take up at least 4 pipes on 6in centers. Add the mask track and curtain track (both of which we have), and that would be maybe another 8 inches. Yah, like the lighting guy is ever gonna give up two electrics pipes so I can have a curved screen. He screams because I got there first and had the screen frame hung on the first pipe; I am sure the minute I retire or die, whichever comes first, he will move the screen six pipes back so he can have his 1st electrics as far down stage as he can get it. But I will haunt him from the grave.

And yah, I was able to get both a masking track and a curtain track hung on the screen frame (and believe me, it wasn't easy --it's all gerry-rigged with spit and bubblegum.)

To preserve space, I used the smallest size alumnium track that ADM makes -- they call it "Specifine." It requires you to use a very light curatin material (I've was able to scrounge up just enough to get double thickness from a dusty old textile storefront on Canal street). This guy who looked like he lived amoung the piles of bolts of fabric, pulled out exactly what I needed, and amazingly, when he unravelled it, it was almost the exactly length we needed. I was afraid to ask how much it cost. It was a beautiful bolt of a very nice cream white satin. Even more amazing, when I did ask how much, he asked how much do I have. I said $250....he thought for a moment and the cinema gods much have smacked him upside the head because he anwered, "Yah, that's about right."!! So I bought it for $250 and I paid a guy in the costume shop another $200 to hem and pleat it correctly (talk about needing math!). And there is was, a spectacular curtain specifically for my screen.

The lightwaight material allows it to be able to ride on a single, small track instead of a double track like you would normally use for velour to overlap in the center. The overlap with the single track is accomplished by clever master carriers that both extend a 6in arm ahead of the carrier and thus overlap the two panels when they meet at the center. I even surprised myself when it actually worked.

Getting the old, mask and curtain motors that I picked up used to work properly was a bitch...slippage on the cables were the biggest problem; I finally had to go to cloth covered aircraft cable. It doesn't stretch so it doesn't throw off the limit switches. All I can say is, it certainly is worth the effort.

Problem is, when clients see how gorgeous that shimmering satin looks when light hits it, they are always clammoring to have the screen flown in to use the curtain as a backdrop, especially when they play on the raised orchestra pit/thrust stage. However, the stage crew knows full well that, sure, they COULD bring in the movie screen to use the curtain as a backdrop for say The Steel Drum/Hip-Hop Scratch Wars, or River Dance, or whatever; but they also know full well that they should they make that fatal mistake, they would each be working the entire show with red hot pokers up their butts for the duration. [Big Grin]

Wise projectionist say: He who does not respect movie screen curtian wind up flying to grid by balls. [Eek!]

[ 08-29-2005, 07:43 AM: Message edited by: Frank Angel ]

Posted by Stephen Furley (Member # 1277) on 08-26-2005, 05:22 AM:

quote: Frank Angel
A fly screen COULD be curved

Yes, but a *roller* screen can't be. Such screens are quite common in multi-purpose venues where the're isn't the height available to fly a screen frame. This tends to be places like arts centres, concert halls etc., rather than theatres. Wyllyotts Centre in Potters Bar and the Concert Hall at the Fairfield Halls in Croydon for example both use large roller screens. Film screenings are relatively rare events at both venues. A roller screen is also used at the Pictureville, Bradford; it comes down in front of the curved Cinerama screen, which is fixed. Thinking about it this may be the widest roller screen I've seen, but I'm not sure of the width; Dick Vaughan, are you there? It's also the only example I can think of where a roller screen is used every day, except for small ones in pubs for video projection of sports events, etc.

Posted by Dick Vaughan (Member # 540) on 08-26-2005, 05:51 AM:

yes I'm here.

Pictureville roller screen is 10.2 metres wide.

We do have a similar Denham roller screen at the IMAX theatre in the Science Museum in London. That one is actually wider, can't remember exact dimensions.

In that case the box containing the screen rests on the screen pit floor out of the IMAX sightlines. When it is used the box is picked up by 3 chain hoists which come down the ceilng. The box is lifted to just above the mid point of the IMAX screen and the screen then rolls down out of it.

Posted by Robert Throop (Member # 61) on 08-26-2005, 08:11 AM:

Does Pictureville have a second set of speakers for the flat screen?
Bob

Posted by Stephen Furley (Member # 1277) on 08-26-2005, 08:18 AM:

Thanks Dick. In that case I have seen a wider one, but only slightly. I think it was 45 feet that Harkness said they could do, some years ago, but I'm not sure I'd want to go that big with one.

What's the Science Museum screen used for?

I've thought of another every day venue that used to have roller screens, though I think there's something more conventional there now. What was the MOMI cinema, now NFT3, had four different roller screens, so they could use whatever surface they wanted for a particular show, or use the space behind the screens for rear projection, or a live presentation; I have seen both done there. Two of the screens were silver and rear, I think the others were matt white and pearlux.

Posted by Dick Vaughan (Member # 540) on 08-26-2005, 08:52 AM:

quote: Robert Throop
Does Pictureville have a second set of speakers for the flat screen?
Bob

Yes we have 5 screen speakers behind the roller screen which fly out when the Cinerama screen is in use. The sub bass speakers are built in to the sound wall behind the cinerama screen an used for both set ups.

You can see it here

Posted by Robert Throop (Member # 61) on 08-27-2005, 08:51 AM:

Do you have two sets of equalizers for your Dolby processor?
Bob

Posted by Tony Ratcliff (Member # 1196) on 09-07-2005, 02:13 PM:

I've got a silver screen here. It was installed in the 70's I think.
It does well. But I DO have a slight hot spot.
And it is dirty with no real way to clean it.

We run House of Wax 3-D most every Halloween - huge crowd pleaser.

Tony

Posted by Daryl C. W. O'Shea (Member # 1303) on 09-07-2005, 09:27 PM:

You'd be really surprised how clean you can get a silver screen with Swiffer wipes (before they came out I used to use similar industrial static wipe cloths).

The last (~26') silver screen I cleaned was extremely dirty. It took about 50 of the Swiffer cloths (attached to the Swiffer floor cleaning pole) to clean it, but it's really clean now.

Posted by Adam Martin (Member # 641) on 09-07-2005, 10:34 PM:

I assume you used Swiffer Dry and not Swiffer Wet?

Posted by Daryl C. W. O'Shea (Member # 1303) on 09-07-2005, 10:37 PM:

Uh, yeah (not too much static when they're wet). Whenever I want wet, I just use my 3000 psi pressure washer. It's great for reaching those high corners of top-masked wall-to-wall screens.

Posted by Dick Vaughan (Member # 540) on 09-08-2005, 09:02 AM:

Knocks all the dirt out of those pesky little holes I bet! [Big Grin]