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Topic: masking systems for home use
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 07-22-2006 06:22 AM
ADC makes a very nice lightweight track and hardware that can be used for your situation. It's the Specifine 1000 extruded aluminum track. As Greg explained, use a piece of 1/8in x 6in x the height of your screen, a piece for both right and left sides. Instead of ply, you might check out masonite; my recollection is that we used it because it was lighter than ply of the same thickness.
These leading edges attach to the master carriers and keep a very straight edge either side of the image. The rest of the black mask material trails behind them. Thing is, be sure to use what I call UltraBlack velour from Rose Brand. I don't see it on their list; when I get to the office I will post the name an product number for you. The UltraBlack is much more light-absorbant than duvotine or even velour. Any image that falls on it is quite obliterated, which is what you want in a mask material.
The nice thing is, this particular UltraBlack material not only absorbes light a lot better than velour, but it is much, MUCH lighter weight. This makes for a mask system that can use the smaller curtain motors. You can get used mask or curtain motors from many of the theatrical supply houses that deal in used equipment pretty cheaply. I got a small ADC curtain motor for my home theatre curtain for $100 used.
Because you are using lightweight materials, you can probably even get away with the using consumer products that are designed to open and close drapes. I think the Home Automation people sell drap motors that should do the job nicely.
If motors are not to your liking or in your budget, do what I did when I was a kid and set up a "home theatre," a couple of decades before anyone ever thought of the term. It was in our basement and I had a sound 16mm projector and ONE film that I forced everyone to watch over and over. I ran the curtian rope along the wall on pulleys and all the way back to the booth where I was able to open and close the curtains by hand. It's not as elegant as a motor, but it works quite well. If you rig a drum and handle, you can crank it instead of hand-over-hand for a smoother movement.
As for the top and bottom mask. If you can't curve the screen, but you want to get that awesome panorama feel that only a curved screen can give, I will let you in on a little secret of mine -- consider the perspective curve. For anyone watching a movie on a screen that has a perspective curve, it will look like the screen is actually curved and it gives them that same "curved" feeling.
All you need to do is have the top and bottom masks bend ever so slightly. The bend is slightly down into the picture area at the center of the screen for the top mask, and bend slightly up into the picture area at the center for the screem for bottom mask. This produces a perspective curve that gives that much-desired panoramic feel as you get from an actual curved screen. How much do you dip all depend on how dramatic a curve you want. You don't want to over due it -- a very slight dip is all you need to great the effect. You don;t want to have purists start screaming at you that you are masking important information (which with an only nominal curve will not do).
The only time anyone will be able to tell -- and they would have to be very astute and into film or photography -- would be when the credits crawl -- they would remain straight lines whilst the top and bottom mask would belie that line as straight rather than the image, which is curving with the screen.
As for movable top and bottom...why would you even consider a movable top/bottom mask? COMMON HEIGHT is the only way to go (and a helluvalot easier).
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 07-22-2006 11:03 PM
Scott, the material from Rose Brand is what they call Acetate/nylon Velvet NFR and it comes in 44/45in widths. They don't seem to have a product number.
The small curtain motor that SmartHome.com offers can pull up to 60 lbs weight. Depending on your screen size, the weight of the velvet mask will surely come under the 60lb limit. It is the leading edge massonite that might make the whole thing a bit heavier than that small curtain motor will be able to pull without stress, although I doubt it. In case it is heavier, you might want to use a simple metal curtain rod threaded through a pocket that you will need to sew in the material, rather than use the heavier massonite boards for the leading edge. The rod will keep the edge straight, with a few encouragements. The trick here is to make sure that the mask material does not rub against the screen and that there is enough space for it to swing freely. This will insure that when the motor stops, the rods in both leading edges will swing enough to keep each edge perfectly perpendicular to the bottom and top masks. Sometimes if the velvet material touches the screen or frame, it will drag and leave the edge at a slight angle. That can be remedied, by taking care all the masking cloth swings free.
In the event that there is simply too much material behind the leading edge so that it does prevent the rod from coming to a perpendicular rest, then you will need to weight down the rods at their bottoms with a fishing line weight. This will cause the rods to act like a pendulum so that no matter where they stop, they will swing true.
The advantage of using a massonite or plywood edge is that it forces the edge to always be true as it can't swing since it is attached to the track at two points on the master carrier. But if you can't use this heavier material for the leading edge due to weight retraints of the motor, then the single rod can be made to work very well, even though it attaches at only one point on the master carrier (thus making it swing more than a two point edge).
Tip: Make sure the track you install has enough play off-screen so that with the masking material gathered together when opened for the scope ratio, all the material can gather off past the edge of the screen. This will avoid the mask material from bunching together and intruding into the screen.
You can also avoid the dedious task of making adjustments between 1.37 flat and scope as to making the mask edges stop exactly where they should. Masks that don't use chain drives these small ones don't) are not quite as accurate in stopping as are the chains. Same with cloth rope as opposed to aircraft cable. But you can avoid worrying about fine tuning the stops, at lease between the flat and scope positions, by allowing the edge of the screen itself to be its own mask.
Hang additional mask velvet material at the screen edges on both the left and right edges of the screen (i.e., the ends of the scope image). This way the movable mask need not be adjusted perfectly to meet the edges of the screen for scope -- just open the mask past the edge of the screen and the screen's scope masks will be reveiled accurately and centered perfectly on both sides.
Perfect stops are accomplished for the smallest aspect ratio setting as well, say 1.37; with simple physical stops that you set in the track itself so the masks must stop at the 1.37 edges exactly where you want them, dead on and even on both sides.
The intermediat stops, like 1.66 or 1.85 will be the ones that could be slightly off (all the inaccuracy is due to the pull cord "give"). The best thing is to use the smallest available plastic coated aircraft cable (they make cloth covered aircraft cable, but it is too thick for this particular size track).
Here's the site for the track: Specifine Curtain Track (ADC)
Here's the site for the curtain motor: SmartHome Curtain motor I seem to recall they had others that were a bit larger than this one; you might want to contact them by phone and see what they've got.
I will post a picture of what the perspective curve in our screen looks like. We get it by making the top and bottom masks out of masonite and cutting the curve into the massonite on a bandsaw; both top and bottom curves must be identical. Best thing is to cut them together.
Once the pieces are cut, then wrap the velvet around them, glueing to the velvet to the masonite and then attaching the massonite to the screen frame. Tip: Glue the velvet to the rear of the massonite, keeping the front that faces the audience free. Attach the massonite to the screen frame (we use long lag bolts that we slightly countersink in the front so that they will not be too visible as bumps in the cloth. Then we lightly spray the front of the massonite with 3M spray adhesive (slow setting type) so that we can drop the cloth over the front of the massonite and glue it to the surface, being careful to minimize any creases as best you can, especially at the curve since that will not be an even fold due to the curve. Try to let the crease that will naturally form at the curve to form on the back of the massonite rather than on the front.
All this is hard to put into text...if you want to talk about it so I can explain it in some sort of English, give me a call: PHONE NUMBER DELETED ![[Smile]](smile.gif)
Frank
[ 07-23-2006, 12:36 AM: Message edited by: Brad Miller ]
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