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Old 8th December 2004, 02:21 AM   #1
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Join Date: Dec 2004
Location: Virginia Beach
Default DIY rear projection surfaces

Anyone have ideas about economical rear projection surfaces?

My theoretical idea is a 8' high x 10.6' wide (or 9 x 12) screen, made of some sort of material that can be rear shot. I would like to make an aluminum frame that can be disassembled. My idea is to make a frame for the front, then 4 other bars go backwards at an angle coming towards the projector.... covered in masking material so there is no ambient light hitting the back. Basically one hellified portable rear projection TV...

This would be used with that 1500 watt projector I was talking about in the other thread :-) Maybe 2000.

I had the idea for small screens of using drafting film....

bedsheets would probably let too much light thru...

A real rear projection surface would probably be stunning... but costly.

Thoughts? What have people tried? I saw other people talking about bedsheets, said it was a no go. Never really found any previous people talking about rear projection screens, but alot of good info about front projection.
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Old 8th December 2004, 04:05 PM   #2
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Join Date: Jul 2004
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Default talked about here

DIY Rear Projection TV
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Old 8th December 2004, 06:11 PM   #3
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Join Date: Dec 2004
Location: Virginia Beach
Default Nice

Nice, I searched but didn't discover that thread. Out of it, to me the most useful information was that about the surface.

I did some hunting, and there is a company that is selling material on eBay by the seller name of dazianfabrics.

86 x 180 - $ 275

That is huge, and while $275 is a bit of money, considering the size of the screen it would yield that isn't too bad. They recommend putting grommets in the material and stretching it to a frame with bungee. So that would cut down on 6" or so. I guess one would attach a black border over the edges.

So 7' high x 15' wide... That would be good enough for backyard movies, or running a video clip about our community website.

I would most likely try to get a first surface mirror from a rear projection TV set and mount it to a frame on wheels so I could shorten the depth of the entire rig a bit (it would take a very large mirror to cut down the throw distance alot).

An overhead triplett lens will indeed focus a 15' wide display correct? Just figure the lens will need to be a bit of distance from the top fresnel, and the whole rig will probably be 15' deep.

I emailed EYE To get the actual arc length on their 1000, 1500 and 2000 watt bulbs.

This will be INSANE if it works.

I did a little research, a commercial 15,000 lumen projector costs $125,000. Moohaha. I want mine to come in under $500.

I looked into keystone correction, it looks like all one has to do is manipulate the top fresnel.
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Old 10th December 2004, 08:06 PM   #4
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Join Date: Jul 2004
Location: england
cool be shaw to tell us about this project when you get fearther this is gona be one cool project but you said about needing to get a mirror from a rear projection would it not be cheaper to buy one from a DIY store you know the sort of thing you hang above your fire place
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Old 10th December 2004, 08:21 PM   #5
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Join Date: Dec 2004
Location: Virginia Beach
Definitly! I have my notes on a Wiki (http://wiki.757.org under Projects then LCD + Overhead projector). It's mega incomplete and no pictures, just notes as I discover new bulbs and hunt for ballasts.

In terms of mirrors... A normal mirror used for home use has the reflective coating applied to the back of the glass. If you use it for projection (at least in the laser world) you end up with a double image. Part of the light reflects off of the first surface (glass) that the light hits, then the remaining light reflects from the rear surface. The proper mirror to use has the reflective coating on the front of the mirror. They are called first surface mirrors. The reflective coating is a bit more vunerable to damage, but the results are instantly obvious when working with lasers... I've used the ones from Michael's Arts and Crafts and they worked for what I was doing... I just figured there are enough worn out RP TV sets to score a mirror from that it shouldn't be a problem.

I'm still digging hard thru the world of ballasts and specialty lamps. I think I might recycle a 400 wat MSR-400 lamp from intellabeam light parts I have already, get the projector working, then move to a MSR-1200 1200 watt lamp, and then look into trying to use a $300 2500 watt HID lamp. I found they are also used in searchlights. That should be able to keep up with cinema projectors!!! (Which apear to use 2000 watt Xenon lamps (don't quote me)). I'm sure my optics won't be as good, but we will see!

I think I've decided to go 4:3 also... I want to edit video in 1024x768, and when it comes to running OPP use dscaler for composite input and upscale with DVD playback software.

If I get this working, I will be tempted to find a location where I can setup a large screen, the 5 watt argon laser system and 4 intellabeams and just tear it up with a multimedia display.
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