8mm Forum: Constant Image Height - adjustable side masking

This is topic Constant Image Height - adjustable side masking in forum General Yak at 8mm Forum.

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Posted by Stuart Reid (Member # 1460) on January 16, 2017, 09:18 AM:

I've started plans for the shed cinema, really excited about having a permanent screen installed. It will run Super 8, 16mm and digital formats (maybe 35mm in the future). I'm trying to work out the best way to add side masking which I can automate. My idea is to take a pair of electric bilnds and invert them 90 degrees at the edge of the screen to effectively run sideways, which I'll control with z-wave blind motors. However, I'm stuck working out ways to keep them tensioned from top to bottom. Anyone have any ideas?

Posted by Paul Adsett (Member # 25) on January 16, 2017, 10:14 AM:

Stuart, you may want to take a look at my CIH set up, which uses two motors, one for the curtains, and one for the side masking. It's simple ,cheap, and works extremely well. All described in this video:

https://www.youtube.com/watch?v=Vo6rAuL4VXc

Posted by Stuart Reid (Member # 1460) on January 16, 2017, 12:00 PM:

Exactly what I'm looking to achieve, Paul.

Posted by Alan Gouger (Member # 31) on January 16, 2017, 12:05 PM:

Very nice video Paul of your lovely Theater. The dimensions of your room do indeed make for a great cinema and the tall ceilings allow placement of the screen a little higher just like in the commercial cinema. Job well done, I love it,Congrats.

Posted by Stuart Reid (Member # 1460) on January 16, 2017, 01:48 PM:

Paul, how close to the screen have you managed to get the masking?

Posted by Evan Samaras (Member # 5070) on January 16, 2017, 01:57 PM:

That's a great set up Paul!

If only I had the room.

I went a little crude with my design. I built the frame from studs, and then connected two standing projector screens to the sides, vertically. They cost me about $20 each. If I recall correctly, they were 40x40 or 50x50. I took apart the projector screens and removed the screen, replacing it with velvet material. I put them back together and had my spring tension for each side. At the end of the velvet is the thinnest piece of wood running from top to bottom, to keep the end straight, and with countersunk magnets attached. From there I carefully placed the opposing countersunk magnets in the correct ratio positions on the studs. I have to move each side one at a time, but it works for me, and didn't cost me much.

Posted by Andrew Woodcock (Member # 3260) on January 16, 2017, 02:47 PM:

Paul's HC room really is perfection. A stunningly beautiful room to view any film, whatever the source.

Posted by Paul Adsett (Member # 25) on January 16, 2017, 04:29 PM:

Stuart, the moveable masking panels are about 1.25ins in front of the screen surface. I have fixed side masking for 2.35, so when showing a 2.35 movie, the moveable masking panels are actually powered out a little wider than 2.35, uncovering the fixed side panels. This enables me to set the motor stop for 4:3 films very accurately and just have an approximate setting for the 2.35 stop, since the motor stops can only be set in steps of about 2.0 ins.
I also have a third masking panel which rolls down from the top of the screen to mask off the occasional 2.55 CinemaScope films, and the even wider Technirama films. So I can mask just about any film format if necessary.
One thing that really helps in all this, is having a digital projector with programmable lens memory. My Panasonic AE4000 can be programmed for 6 aspect ratios, for picture size, picture vertical and horizontal position, and focus, so you can switch between academy, widescreen and scope etc, all at the push of a button. If you are in the market for a digital projector I would really recommend that you get this feature, which is not offered on all projectors. It makes a huge difference.

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