UPDATE 29/01/2007: see post #64 for pictures of the completed project! http://www.lumenlab.com/forums/index.php?s...st&p=206846

This can be useful for somebody looking at building some kind of rear projection system.

I built a 60" rear projection using the Lumenlab factory-made projector. I am very pleased with the results considering the investment and the size of the screen. I bought the projector used from nmaxima2k1 for $450. I am renovating my basement, putting in new flooring, and I was planning to build my own wall unit, up to the ceiling, with very large cabinets to use as storage for toys, ski equipments and stuff like that. In designing the wall unit, I was planning on putting a large TV in the middle of the unit and thats how somehow I encountered this site browsing online!! Anyway, my wall unit is not completed yet since I have been working on that rear projection setup first, and since its gonna be the central part.

Here are my components:

1. LL factory-made projector, 480p definition: $450
2. Standard 1/8" (3mm) glass mirror, 36"x49": $60
3. Screen is a polyester-based (mylar) thin drawing plastic-like sheet, frosted on both sides (you buy these off large rolls in arts and crafts strores), $5 per foot: $20
4. One spray can of Frosted Glass "Rust-Oleum Specialty" paint bought at Home Depot: $6.99
5. VGA transcoder bought on Ebay for $30

One coat of frosted glass spray paint (fully translucent) was applied to the back of the polyester-based sheet in order to reduce hot spotting to a very acceptable level. I showed the results to a lot of people and it seems like many don't even notice any hot spotting at all. Hot spotting is small but present. The picture quality is definitely better than that of some older rear projection TVs I've seen.

The most difficult thing was to find an acceptable RP screen for my setup. And I may not even be done as I ordered a roll of cellulose acetate from the internet at $18.99 to see if I get better results. I already tried several different materials for a RP screen. I started with a piece of white plexiglass which rendered a decent image but impossible to focus the image. Tried two or three different types drawing papers and a shower curtain, a free sample of sandblasted glass and other free samples of many different types of plexiglass... Even tried an old CRT Zenith RP TV lenticular screen.

The brighter image was the Zenith RP TV fresnel screen, so bright it was the real tv effect. However the screen was smaller than 60" and although brighter, the wide angle views were terrible. Also, I would constantly find some imperfections on the screen as the images change. Second in brightness was the sandblasted glass, with the same problems with wide angle viewing. Also, the sand used needs to be very very fine as my sample was made of 100 grit sand and it was not enough for precise viewing. Also, someone would need to sandblast the glass forever in order to reduce hot spotting to acceptable levels, resulting in a dimmer image ... by the way, I would not recommend sandblasted glass as there are other cheaper light diffusers and methods to refract light rays out there.

The screen I am using now is dimmer but more like a "cinema effect" where wide angles are not a problem at all, and an excellent picture can be viewed with a fair amount of light in the room; however it is better when light is controlled so that light is not aiming right at the screen. Plus, the price is very low!!! However, unlike when I used the Zenith RP TV panel, there is now a level of lighting (especially too much sunlight) where the picture gets overly degraded. With this screen, it is very easy to get a clear focused image with clear picture details. Very good for the price.

As for the projector, up to now I am extremely happy with it. Price is good and the image quality is there. Fan noise is annoying so thank god I am rear projecting as it cut down much of the noise. However, it would be great if the projector was brighter. Luckily there are brightness, contrast and saturation adjustments that can be performed with the remote control...

Enough talking, here are some pics... the vertical lines in the screenshots are from the VGA transcoder and cannot really be seen on the real thing. Also, I'm sure that I could take better screenshots than that! Sorry about the size of the images, they are blown up way above their real size and I don't know why.





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{edited bt pagercam to make image size reasonable, please use smaller images next time}

Here are some better screenshots, with some lights on. Cartoons look great on this projector. There are two 75W spotlights on (along the right hand wall), and three 40W normal bulbs on (up above the bar in the back). There is a bit of sunlight going through the blinds as well.

Excellent job, very very nice and a cheap way to get a big screen.
Another person retrofitted a commercial RPTV and found that it didn't have the wash out problems that a front projector ussually does. How does yours do with high ambient light???

I tried using an RPTV front panel -- an old 49" Zenith RPTV screen -- and the image is so bright no amount of light could kill it. But wide angle viewing is unacceptable. Not like today's screen. I guess it would be definitely worth trying a 60" RPTV screen, but they are just very hard to find. Also, the picture on an RPTV screen is very different, almost like shining out. My screen picture is more like "cinema", dimmer but kind of fuller. Hard to explain.

As for my screen, I am happy with the image, however as you pointed out, with high ambient light -- for example some high exposure to sunlight -- the image starts to wash out. Maybe if I had some ways to prevent ambient light to "shine" through my screen it would help? I still can have some good lighting in the room without problem, enough to read. In daytime, I can open the curtains of the far away window and have some spotlights on. "Controlled" lighting is fine.

Here are some screenshots of the World Cup final with a good amount lighting in the room... First, the lights that were turned on in the room (its a big room):



Now the screenshots (its TV so I can't pause the image which creates bluriness on the picture):





This rear projection screen does a pretty good job for a total of $26.99!

What size are you projecting? do you have a diagram of your setup. Looks Good!

The projection size is slightly smaller than 60" diagonal at a 4:3 aspect ratio. I don't have a diagram, but if you look at the above picture, the projector sits in the left-hand side closet, the mirror (36"x49") is put against the large brown wood panel inside the enclosure (36"x48") at a 45 degree angle. Also, I put 3 pieces of wood around the light path of the projector between the closet and the enclosure to protect the projection against ambient light.

I'm genuinely interested in this, wow!

Can you please show how the projector is installed from the back, and a few pictures with sunlight in the room would be greatly appreciated.

Thanks a lot, great job!

The projector sits on a shelf in the left-hand side closet, where it projects on the mirror inside the enclosure. Pictures of the projector on its shelf while projecting on the mirror through the holes (the holes are visible in the first picture posted above):



Now, a screenshot without/with sunlight:

Without sunlight:



With both curtains open (sunlighted room):



You can see that the image starts to wash out. Dark images made of black levels obviously wash out more than the image you see here.

Nice work!

I emailed four manufacturers of rear projection screens/films found on the net: the lowest quote I received was $300 (not including shipping) from Gerriets International and that was their lower quality material, called "Aria..." It was $500 and up for their quality stuff. But I don't even know if thats really much better than what I am using anyway...

I found a link to the material I use for screen material, if someone wants to try it. I have been using it for a while and its performing amazingly well for the price.
http://www.omerdeserres.com/en/index.asp?s...mp;produit=2249

You have to go to an actual Arts and Crafts store and they sell it off a big roll. The store I bought it from sells it 42" wide $5 per foot. So you can make quite a big RP screen for cheap.

But I am still open to trying new material...so if someone else on this forum is rear projecting I would really like to know what screen material you use.

I'm wondering here.... thinking about a rp myself.... Durachko had an idea to increase the eveness(vignetting) of a standard front projecting pj by printing a mask to be placed over the lcd or fresnel, darker in the middle then lightening to nothing at the corners, generally no-one has tried this simply because you lose lumens...but I'm thinking that maybe something like this might decrease hotspotting using the original material you mention without anything sprayed on it(which lessens lumens anyway) ....when you sprayed the paint over the material did you do it evenly? wondering if you could do it heavier in the middle tapering off to none at the corners... although I think the printing a small version(using a "negative" of your projection for the template)... you could take a picture of a blank white screen that would show the hotspotting, then negative it, then print on a transparency , it would match your hotpotting exactly that way..does this make any sense?

I see what you mean, however the location of the hotspot on the screen depends on the viewing angle. If you sit facing the middle of the screen, then the hotspot will be in the middle. If you sit at the right of the screen, then the hotspot is facing you on the right, etc. Hotspotting appears because of the reflection in the mirror of "collateral" light created by the projector (without a screen, if you look in the mirror you see the same thing as if you look directly at a projector, ie like a light bulb). When you change position, then you see this light somewhere else in the mirror...and its corresponding hotspot.

For example, if I move and look at the screen at a 45 degree angle, I see no hotspot, just a beautiful flat image, but dimmer because I am at a wide angle. This is because if the screen was removed, at this wide angle I would not be able to see the projector lense at all in the mirror. If I had an horizontal keystone correction I would be able to completely eliminate hotspotting for significant viewing angles.

My pj has vertical keystone correction only, so this would be very helpful if I was rear projecting vertically (ex: projector under the screen) because I could project at a different angle using the keystone correction and placing the screen slightly tilted towards the floor. Then I would not have to worry about hotspotting.

As for the corners of the image being dimmer, this happened whether front or rear projection and totally depends on what I am projecting... Not really noticable with a 480p feed, but it is slightly noticable when its analog TV and the image is darker. Bright images are never a problem!

As for the paint, this is just to block some of that "collateral" light created by the projector... but it also blocks some of the good light so its good to put as less as possible, and none if hotspoting is not really a problem.

ah well, it was just an idea, never having seen hotspotting I didn't know how it worked....

have you gotten the cellulose acetate film yet? I'm thinking of making a portable frame with some kind of film(like you are using) and putting the pj behind the screen aiming directly at it(my dining room is directly in line with our viewing positions so the pj would be behind the screen in the dining room) ...my wife really likes the idea... let us know of any furthe eperiments you do... interesting stuff...

Yes I did receive and try the cellulose acetate from Graffix: cellulose acetate film is more glossy but unfortunately its only frosted on one side so there is not enough frosting at all. From what I can tell the best stuff is still the mylar (a.k.a. polyester-based) film paper. Its really cheap to try it (about 20$!). Also, in your case, if you have vertical keystone correction on your pj, you will be able to easily eliminate hotspotting by avoiding to place your projector in the viewers' line of sight.

However I have a question: if you put your pj in the dining room and use a portable RP screen, I guess you will still need to be pretty much in the dark and have to set up the pj each time you want to use it... pretty much like doing front projection... so what are the advantages of using rear projection in your case?

hi there,

I've got the exact same projector, but I have a major problem getting perfectly square corners and razor sharp image on the whole surface.

Would you have any trick for me please ?

I see you've put a book under the bottom of it ?!

Thank you in advance and keep up the good work

what kind of arts/crafts store did you buy it at? went to a couple yesterday and couldn't find anything like that....well, mainly it gets the projector out of the living room(and the tv for that matter), mostly for aesthetic purposes....

I see... I bought it at Wallack's ( http://www.wallacks.ca/ ) which is the largest retailer of art supplies in my city (Ottawa). There are six Wallacks stores in the city and only the two biggest carry the big rolls. Another retailer that has it is Loomis Art Store / Omer de Serres (they are affiliated, see the product link above) and have many stores all over Canada (however, their rolls are only 36 inches wide compared to 42'' at Wallacks)... These are the kind of stores where architects go to buy their quality drafting materials.

If you don't live in a big city or you can't locate that stuff, I could ship it to you if you want (I guess I could roll the piece in some kind of cardboard tube, would be light so I guess prob. cheap to ship?)

well, I will have to hit the art store on campus, I imagine they might have it or know where it can be gotten.... thanks for the offer though! may have to take you up on it if I tap otu here....

Mmm I just googled the product name (Transilmatte Matte Polyester Film) and it seems like it is manufactured in Canada, which would explain why it was so easy for me to find it and difficult for you:

http://www.transilwrap-canada.com/Transilmatte.htm

As you can see in the description it is a light diffusion material, which explains why it works so well for RP.

Maybe you could contact customer service and see who retails that product in your country (U.S.?)

any chance getting a reply please ?

merci lesavoir

just did that, thanks..hey is this really thin stuff? like plastic wrap, aluminum foil etc... or thicker, googling frosted mylar, I see people using it to make stencils and drawing on it and froim the sounds, they are using somehing that is fairly stiff

I've never had problems with my corners, although the projector needs to be completely horizontally perpendicular to the screen since there is no horizontal keystone correction. Also you may want to play with the vertical keystone on your pj, maybe thats your problem?? And play with the position of your projector and the focus?

Also, if you didn't buy your pj from Lumenlab, it may be your pj that is causing the problem since Brainchild reported some problems with focusing the corners when testing the Ally projector. The projector I have was not manufactured by Ally, although the case is the same.

The book under my projector is just to vertically center the image on my screen.

As for razor sharp image...the screen can make a difference too. Maybe you could try using a different screen?

If you could post a picture of your setup and your projected image, it would help as well

Its really THIN (Thickness: 0.003''). Paper thin. But its stable, like plastic. It doesn't tear easily so its really easy to stretch. Its not like aluminium foil since it doesn't wrinkle that easily. Its stiff enough so that it can be rolled and unrolled easily without creating wrinkles.

ok thanks for the swift reply.

I have the exact same as yours, with the 640*480 screen and all.
it comes from the same factory as yours, with the dolphin logo on top of it.

I've tried to mess up with the "keystone" feature but it didn't help much.

I've read that it's a good idea to set the keystone to 5 degrees, then try to move the projector until it's in the proper position.

I will run more tests and post some pics, thanks for your help

BTW, if you wanna get kick ass vivd colors, grab a "29963" light bulb from "Venture Lighting". It's 6500 Kelvin degrees and the quality is just awesome...I suspect the original built-in bulb to be 4200K, and at least this one is UVSTOP and 10% brighter

talk to your later

thanks, thats what I thought it was....been looking at some Rosco rear projection material, have you ever seen any of that" they use it in stage productions, about 15$ per yard, 55" wide....

Thanks a lot for the light bulb information... I will look into that later today...I don't think that this pj has a UV filter so putting a UVSTOP bulb would block UV rays, right?

As for your image, what is your feed? progressive scan DVD format (480p) or analog 480i? Since I have been using the VGA transcoder, my image is sharper and brighter. Maybe you are watching TV through the video input (yellow) of your pj, which doesn't help at all. DVDs for example: if you use the component output (with component cables) of a progressive scan DVD player through a VGA transcoder and plugged into the VGA input of your pj, then you should be able to get a razor sharp image because there is no interlacing/de-interlacing involved.

If you use the video input (yellow) or S-video input of your pj, the DVD player first interlace the 480p signal of your DVD, which is then de-interlaced by your pj!!! which means you're losing image quality. Also, for watching TV, I use the de-interlacer built in my DVD recorder which does a much better job than the de-interlacer of the pj. Hope that helps.

Wow, I have never seen that. 15$ per yard would be 5$ per feet, right? About the same price as my stuff. How can I order a yard? For this price, I wouldn't mind trying it.

http://www.stagetechnology.com/catalog/items.cfm?SSCID=760

they also list something called "rosco light translucent screen" which soulds really interesting I googled "rear projection screen material" but I did it for the "Groups" not the web, a lot of people asking for cheap rear projection materials for stage productions, now, before you go hog wild, I'll tell you (n case you don;t know or don't go to the theatre) that stage lights are reeeeeaaallllllly bright, and they generally project not very detailed stuff on them, the "twin white" says it can be used equally well for front or rear projection oddly enough, they have greay and black also, but from what I've read they need "strong" light(their words
and on another note, I'm having more luck finding "drafting film" which is .003 mylar, comes in single matte or double matte...seems to be essentaly what you have..double matte is better you think? I did by a one dollar translucent shower curtain yesterday and a can of krylon frosted glass (no rustoleum around)

no, I only use the VGA input with a high quality shielded cable, an nvidia videocard set to 640x480 60hz and commercial DVD's, with "cyberlink eagle vision 2" enabled in PowerDVD7 to get uber-cripsy colors

I believe the original light bulb is not UVSTOP(as it was hurting my eyes), and I've read that the tampered glass they use is of very low quality, so that could damage the LCD panel after a while.

so better be on the safe side and ditch this noname low quality bulb to get UVSTOP(around 70% are blocked, so I hope the tampered glass will take care of the rest) and more real to life colors, as 6500K is the reference for white balance found in every commercial pj around

the picture is not yellowish anymore, just make sure to click on "AUTO" in the OSD whenever you switch movies.

I've only had this pj for a few days, so a better option might be to click on "AUTO" on a test pattern picture but I haven't tried, considering my tests are not quite finished yet..

if only they didn't put that keystone knob that scr*ws everything up

Mine is double matte (i.e. frosted on both sides). I did try the one dollar white shower curtain and its wasn't doing a very good job, wasn't refracting enough light...

I will try to order a yard of the Rosco RP screen... Although they have so many different models, I will have to choose one!

well, probably either he twin white or the light translucent, tell you what, you order one I'll order the other

so tell me, do you click on "AUTO" in the OSD each time you switch movies to get optimal results, or did you use a test pattern to set it once for all ?

I have never used AUTO... I just put brightness, contrast and saturation at 55%... and if the whites or colors are too bright, I would reduce the contrast... I will try AUTO tonight and see what it does!

I called a light bulb store and they would charge me 74$ for that Venture light bulb...is that the normal price? And a 4000K with UVstop is 45$.

don't forget that the light bulb is "overvolted" in our pj(from 150W to 175/200W roughly because of the 250W balast), so the colors temperature is lowered.

basically, a 6500K bulb will give us 6000K but a 4200K will give something like 3500K which is very YELLOW, like these cheap halogen bulbs. major waste of money if you ask me!

anyway google it up, it's a lot cheaper

I paid 26 EUR(around $30)/piece for 3 bulbs here in europe, and it's a US company so that would be even cheaper there I guess

BTW, I can't believe you've never had any problem with the keystone thingie

I found an online store which carries the bulb for $35 : http://www.atlaslightingsupply.com/MHDoubleEnded.html
Are you sure its worth the money and the trouble of ordering and buying this bulb? The pj came with a spare bulb so I don't really need a spare right now... will I get only a 10% brighter image?

BTW, I tried ''Auto Config'' and the ''Auto Colors'' in the OSD menu... didn't make that much of a difference, and I had to readjust the focus afterward! I'm not sure these are the options that you were talking about...

I had a look at the description of the screens there: http://www.rosco.com/us/screens/roscoscreen.asp

So basically the 'twin white' is the material that is the most similar to what I am using (180 deg. viewing cone, ambient light around the screen may affect the image quality).

The 'grey' projection screen is brighter than the 'twin white' but the viewing cone is limited to 60 deg.

The 'light translucent' screen is not for me because I cannot place the pojector at an angle in order to avoid hotspotting. In theory, you should be able to use it if you use keystoning to put your projector outside your line of sight.

Therefore I am leaning towards the 'grey' screen...although 60 degrees is not much, and I have a feeling it might be to bright resulting in hotspotting...I will call them tomorrow to see if their shipping rates are reasonable.

well considering the original light bulbs are not UVSTOP and the Venture is 10% brighter and 6500K. I'd definitely say yes
Look at the LL shop, they only sell 6500K bulbs for a reason

When you'll see the colors difference, you'll thank me for it.

humm....I can't believe we don't have the same OSD ?!
shoot me a picture of your OSD if you can.
at the bottom in the middle I got an option called "AUTO"
and it plays around with the phase and all kind of options to maximise the picture, balancing the colors and brightness/contrast as well, gotta love it!

It's kinda weird you had to refocus the image, though

ok this is with an OSRAM 5200K UVSTOP bulb :

this is with the Venture 6500K UVSTOP bulb :



You can see that the colors are a lot colder with the venture, much more realistic.

I didn't bother taking photos with the original bulb as it is not UVSTOP and it was hurting my eyes very badly, but it was even warmer than the OSRAM anyway, which leads me to believe that it is indeed 4200K.

They would charge me $20 for shipping (UPS)... thats 35$ total. Also its UPS so I don't really know what their custom brokerage fees will be like...can be as high as $30 if they do like Fedex. I have to think about that a little bit longer...

so did my pictures sell you ?
I'm surprised you didn't reply...

I'm not a salesman or anything, just a happy camper now that I've got them

show me a pic of your OSD if you can.

Yeah, I called the store that I found online who had the bulb for $35 and they were really nice, I am still waiting for their reply though; they had to inquire about shipping since I am in Canada... I am interested in that bulb especially because of the UV shield since I am rear projecting, as you know...

Here are pictures of the OSD menu

oops, we definitely don't have the same OSD

Does you panel accept anything higher than 60Hz at 640x480 ?

Mine flickers like crazy if I try

I don't know

you don't use the VGA input at all ?
that's the only way to get top notch quality...

how do you feed your dvd's ? composite ?

I use the VGA input through a VGA transcoder, the transcoder is set at 480p, and that is what my DVD player/recorder outputs...

right, you told me already
well I tried the composite input on the pj and it really looked like sh*t, washed out colors and noisy picture

nothing beats native VGA

I'll run more tests about the keystone thingie later this week, and I'll make some photos in case you could help me on that one buddy

I ordered the ROSCO GREY rear projection screen... 1 yard, 55" wide, $27.50 at a local store... I should have it sometimes next week. I'll post my results.