It seems no matter what is done, the image quality is severly degraded and you'd have to be insane not to use front projection instead.

With more see through screens, its easier to see through, but too much light just goes right through it causing hotspoting and dim edges. With more solid screens, the image is more evenly distributed, but all the light is reflected and filtered out from the other side.

Using a frosted glass in attempt to refract the light without blocking out any doesn't work well because it only points parts of the image towards you, and parts away from you. Using a finer refraction only causes your brain to combine the bright and dark into a dim image.

So how can rear projection possibly work?

I guess we just need to find a way to duplicate professional rear projection screens the way brain duplicated video projectors.

Good luck!!!

There is so much clever people on this forum im sure someone will figure it out

What about that material that is on pictures, that when u tilt it up it's one pic, and
when u tilt it down it's another pic? e.g.; guy hold bat...flip down..guy swing...
i'm just guessing,.sorry if it sounds dumb.

That's actually quite close to the way the old lenticular screens in RPTV's work. The quality is low though. If anyone knows the film used in modern high resolution RPTV's I'd like to know. I've seen some in local stores that are just amazing. High uniformity, resolution, and viewing angle nearly rivaling the plasmas. There must be a high quality, cost effective solution for the DIYer.

I was thinking of something like that. Not sure where to get it though.

Well I think Rear Projection is not necessarily a hopeless cause, but it will never be as good as front projection on a simple white screen.

But I have mentioned earlier that rear projection seems to be very sensitive to light, and decreasing the light decreases the differance in quality between front and rear projection, the contrast isn't bad at all, but images just loose their radiance. Its like watching a movie with sunglasses on.

I think it may be tolerable if you use a relfector and make the room very dark. But it won't be as good as front projection. Really better keystone correction is what we need.

Can't beat them, join em?


Why don't you try to locate a parts supplier or TV repair place that would be able to source you the screens from a RPTV?

I don't know if you are going to find the solution with a single layer either, I am sure my Toshiba set has two or three screens in there.

Someone here already used a screen from a rear projection tv and said it works great, but I doubt you can get them very big. Might be more practicle though since rear projection takes up a lot of space.

the newer projector tv's with their slimmer build now also seem to have nicer screens...up to like 61' plus...but i guess the lumens will also have to be in concern, i'm only sayin this cuz of the DLP doohickies.i'm still thinking that the RPTV's can still be possible..somehow.

IMO, it's probably inferior to consumer TVs in image quality, but getting a good picture should just be a matter of finding the right material. Which won't be found without someone with a few hundred bucks+hours to spend on trying every weird material they can get their hands on.

Have you gotten anything that equals Jo's consumer RPscreen material?

Suggestion: Try buying a sheet of home depot plexiglass, chopping it up into many pieces, and trying various combinations of paint, other materials (shower curtains, window curtains, various types of plastic), and perhaps sanding. I heard someone mention using very thin coats of "frosted glass" lookalike clearcoat.

You may also want to try experimenting with more advanced optics - a condensor for light evenness, a bigger bulb, etc. Avoid angles that require keystoning if you're using glass/acrylic to mount your screen material, as you'll get much more scattering of light inside.

I guess I never really looked here but whats wrong with the rear pj screen material but I heard this stuff worked? the rear pj stuff http://www.dazian.com/

What exactly is a condernsor and where could we get one that big?

Has any one tried sand blasted clear acrylic sheet, or sandblasted glass?

No, i did not get a chance to try that because i do not have the resources to make it, but that was one option i read about, If someone has access to a sand blaster then give it a go, prob. sandblasted glass would be best.

Joe

I recon the other good thing about sandblasted glass would be if you had the sandblasted side on the outside, you would have no problems with reflected lights or images in the room. Unlike a normal TV screen

Has glass etching been looked into? Here is a link to chemical etching.

Screen for REAR Projection

Check this out http://www.dazian.com/html/projection_screens.html


Surface: Textured Grey PVC

The Grey Rear Projection cinema or theater screen offers an unusual high gain with a wide viewing angle. The specially textured surface reduces light washout. Gain of 1.6 on axis.

Been there done that, Look at my Whole LLRPTV Thread, I have Pictures and all.

Joe

i see that the later pics look good. i am thinking about this type of build down the road. do i understand this uses a simple 15 pj optics? also the size of the large fs mirror looks pricey. thanks for any help folks
ron

Actually those are just front projection test shots of the vertical projector. I'm not sure why they were posted there.

i see. thanks for the answer. i also read alot about the final image is less than perfect. is this all from the screen? should i be asking all these things under the screen topic section of rptv?

Not sure. The whole forum is about rear projection which is all about the screen so I guess its ok to post it anywhere.

Have any of you looked at Goo Systems. They came out with a rear projection sprayon paint that looks pretty cool. I just bought some and did a test piece on 1/4" thick clear acrylic. Very little light passes through and the image is awesome. I needed to perfect my ability to spray and even coating, but I expect my next go around to be near perfect. Web site is goosystems.com. The rear projection stuff is new and works as advertised as far as i can tell.

Pics please? The goosystems galery pics look too good to be true. Especially since they're in a brightly lit room!

Seems they have a pretty wide variety of products at all differant prices. How much was the one you got?

has anyone tried this goo stuff yet?

You can actually order samples for 20.00 plus free shipping. Might be worth 20.00 to try it out.

GooThings.com

8"X12" Sample Boards (set of 3)
Code: 5906
Price: $20.00
Quantity in Basket: none

Free Shipping

8"X12" Sample Boards (set of 3) covered in CRT White, Digital Grey Lite, and Digital Grey coatings. Great for testing the Screen Goo product with the projector in your lighting environment.

I've seen it reviewed, and the reviews said it was 'just ok'. People have made better solutions by mixing their own paint combinations. The pix on the website are fake.

Have you considered using DNP's 'black bead' screen? It is offered in a smaller size in the US (33"....suitable for the bedroom or office) by a company called LanternScreen (http://www.lanternscreen.com) or in larger (and more expensive) sizes by DNP in Denmark. The screen is only 1/8" thick and demonstrates a large on-axis gain (sorry, don't remember the numbers). I'll be curious to see what happens with that one.
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I haven't been involved in the RPTV scene, but the VP of marketing at Professional Plastics e-mailed me about screens they now make for rear projection. Bit spendy, but if you are really intent on a tv like this check it out:

http://www.professionalplastics.com/cgi-bi...prname=Acrylite

Screen size is 49" x 97" and comes in Non tint ($294), Light Grey ($312) and Dark Grey ($306)

Thats a reasonable price if it works well. I think if you want quality your going to have to fork over some dough. I don't think we'll ever find a diy rptv material because it requires super small cuts. If we could do that we could make our own fresnels.

I called the local company here and ordered a development kit wih a test sample in it. They will send to me soon and hope we can test to see how it works compared to the other materials i have tested.

Joe

I got the Sample of the Acrylite RP material, It is anout 1/8" some type of plexi. here are the test results.

If you remember my RPTV i was building and have in storage the bottom is the screen from it and the top is a small sample of the Acrylite sende to me.

RP material Vs. Acrylite..

1st is with lights on and the light is behind the materials slightly so you could imagine if the whole things was blacked out with the rptv cabinet.

2nd is a straight on shot.

3rd is at 45 deg.

How much is this stuff and how do you buy it? 4x8 panels? Do you think it could work for the standard LL PJ with out hot spottin' ? Your sample seems to have good ambient light performance.

Joe,

Looks like your onto something here !

To me thats at least 50% better all round picture, how do good do you think it looks ?

Is it as good as say commercial RPTV, and more importantly could you be happy with it sitting in your lounge on a permanent basis.


Cheers

I think by far this is the best material for a DIY RPTV, i think it would be about 80% of a real rptv. I was very surprised at its performance. I would be happy with it for sure, However the cost right now is about 300.00 for the 49"x97".


Joe

We will will just have to make some then.

DJ

Thats reasonable in my oppinion. But at that point you'd be spending close to a thousand dollars if you include the cost of the projector. You might be able to get a nice rp tv for that price.

Wow, nice results!

Joe - How does this compare in your opinion to a front projection with ambient lighting and also with complete dark?

ambient light it is better and in the dark it pops out with glow brightness. this by far is better than any material i have tested for RPTV.

How does it compare to front projection though? Better? Or almost as good?

Would you compare this material to any standard front projection material you are familiar with? I'm curious how this material stacks up in terms of brightness, hotspotting, contrast, etc.

Thanks, Tom