I'm trying to use my projector with a rear projection screen. I've tried the Dazian material and except for wrinkles and creases from shipping it seems to be good enough for me (I'm easy to please). I'll mainly be displaying a Linux computer desktop and computer graphics.

Does anyone know if I can reverse the image via the computer or graphics card so that it appears correct on the RP screen?

I'd rather not reverse the LCD panel in my projector because we use it to watch movies on our den wall regularly also.

Suggestions?

Thanks,
Ookpic

ok just found out heres what u can do.......

flip the LCD in the projector ....so that RP comes out the right way

then to watch movies (not using rear projection) on your wall......install Zoom Player and go settings>filter control> ....set all filters to VMR9 and tick the box that says "flip horizontally" then restart bs player.......

BS player can play DVD's and divx etc...so u can use it for everything to play movies flipped so that its the right way up

maybe there is a program that can just flip all windows ...but i dont know...only know of programs that will rotate not flip

Could you use a mirror?

Maybe this will give you some ideas, and yes a mirror will work.

http://www.lumenlab.com/forums/index.php?showtopic=1784

Joe

I tried a mirror and it worked fine. I have room to position it in front of the box so I don't have to make any changes to the projector. For now I've used an extra wall mirror I had in the attic.

I only ran into one problem. When I tried positioning the mirror very close to the projection lens (so the mirror could be smaller) I couldn't get the screen image to focus. Backing up more from the projection lens solved that problem but I don't know why.

Thanks for the suggestions.

Ookpic

Probably due to the fact that you are using a conventional rear surface mirror, the double image is more pronounced when the mirror is closer. Getting a front surface mirror should remedy this.

I got the front surface mirror and you were correct - I can now put the mirror as close as I want to the lens and it stays in focus. It also brightened and sharpened the picture a bit over the rear surface mirror. (I got the mirror from the lumenlab store - very nicely packed!).

I'll try to upload a couple of pictures of the results.

Thanks,
Ookpic

Here's the standard Fifth Element picture. The test screen is about 7 feet wide. I have it hanging from a wooden dowel and you can notice a crease in the middle. I'll get rid of the crease when I mount the material properly.

Well .. I can't seem to upload the picture - I get an error about exceeding max size - perhaps the file is too big (199kb)?

I guess you'll have to take my word for it that the picture looks not bad.

Cheers,

Ookpic

I'll try again with a smaller picture (58kb) ... looks like that did it!

Here's one with ambient lighting and a couple of my kids... the lowres colors that are apparent especially in the ceiling over the clipboards are a result of reducing the size of the jpeg picture so I could upload it to the forum.

WOW, that looks nice. How much ambient lighting is in that picture? Is the brightness good enough to watch with a little daylight coming in through shades?

Thanks.

Thanks ... the material worked better than I expected it to.

There were two light sources in the room - both on the left side. One was a 60W bulb and the other was a fluorescent bench lamp (probably about 60W also).

A little daylight may be okay as long as it is not coming from behind the screen. I think that too much would probably wash out the picture. It may depend on the movie also -- Monsters, Inc is relatively bright.

Ookpic

Where did you get that screen material and how much was it?

Also, just curious, but do you have any comparison shots with front projection (on BO cloth or something) for that projector with the same ambient lighting?

DAZIAN CLOTH

http://www.dazian.com/html/projection_screens.html

Just for clarity, you are using the gray rear projection screen and not some other dazian screen material, correct?

Yes, I'm using the gray rear projection material. ($55/yard cut at 86 inches wide).

If you order it try to get them to send it to you on a roll. Mine came in a box - rolled up and then folded - which resulted in what appears to be permanent damage to the material. I complained to Dazian but didn't get a response.

I don't have a comparable front projection picture - maybe I'll try to get one this evening - I have a roll of blackout cloth that might do.

Thanks for the info. Am I right in assuming that in ambient lighting, RP produces a better picture than Front Projection?

I've heard that RP is less sensitive to ambient.

I did a test this evening to compare RP and FP with as close as I could get to the same ambient lighting ... results follow.

I hung some blackout cloth so that the ambient light would be approximately the same distance and angle from the screen as in the previous RP Monsters, INC picture.

The blackout cloth was a bit smaller than my gray RP screen so for a fair comparison I let the picture fall off the edge so that the picture size would be approximately the same.

Here is what it looked like with no ambient lighting.

Here are the workbench lights I was using to provide ambient light. (the corner of the screen on the right is RP).

And here is the front projection screen with the ambient lighting turned on.

The picture looked more washed out especially on the right side which was closer to the lights.

Wow, the RP pics look much better with ambient lighting. Hmmm... now I have to decide whether or not I want a RP setup, a FP setup, or both.

Thanks for the comparison pics, they are very helpful.

Normally the FP picture doesn't look this bad with ambient lighting.

The lights were very bright and only a few feet from the screen. Because I couldn't hang the two screens in exactly the same place there may have been some effect from the different light angle also.

I'll try another test this weekend under different conditions (maybe sunlight).

I've tried a test comparing RP and FP with ambient sunlight. It didn't show as much difference as I expected - not nearly as much as my previous test with the workbench lights.

I cleared enough space in my garage to set up the screen 12 feet from the garage door. In this configuration I had enough room behind the screen to rear project a 50 inch wide picture. I had more room in front but for comparison I kept the picture width at 50 inches for the front projection also.

In both rear projection and front projection test setups I took a series of snapshots with the garage door opening at 7ft (fully open), 4ft, 2ft, 1ft, 6 inches, and fully closed.

All the tests were performed between 9:45am and 10:15am. At the time there were no clouds blocking the sun.

In my opinion the RP series of pictures are only marginally better than the FP ones.

Rear projection test setup

Front Projection Test Setup

pics

jmrguy,

I don't know what to conclude re: FP vs RP.

It may be that I didn't reproduce the relative positions between the screen and the workbench lights well enough in my first test. Alternatively, perhaps a concentrated light from the side produces more variation between RP and FP than a more diffuse ambient light.

Perhaps someone else who has more experience with RP vs FP can provide some advice.

Ookpic

Thanks for the comparison shots. Maybe someone can provide more insight.

For the RP, if you use a giant fresnel lens behind some sort of solid transparent professional screen, it will be much better, like the commercial RP TVs out there. Otherwise, if you use some sort of fabric, it'll be just as good as FP.

Great job Ookpic. This is very informative. To me the RPTV version in a bit better but not drastically so. You did a good control test and thats what we need to see more of, too often we just buy a part or adjust things with out any sort of measurement or comparison so as a group we are not getting any closer to a solid recommended design just a lot of individual designs.

Thanks. I think there is a lot of good testing going on and there is some discussion of the conclusions but not much explicit posting of the results. And, as you say, not a lot of (at least attempted) control tests.

Perhaps someone could set up an area for this purpose. Any moderators listening - if so, what do you think?

Ookpic

I agree. There should be an area for people to put up different comparison shots that they have taken.

Ookpic; Nice job with your controlled experiment! The results are extremely informative.

I beleive that you would see a much more significant difference with a more highly engineered RP screen. The reason that commercial RP systems do better in higher abient light is that their screens absorb most of the the light from the front while transmitting most of the light from the back. A white sheet is going to block more of the light from the PJ while reflecting more of the ambient light. Check out this product from 3M (called Vikuiti)
Vikuiti XRVS screens
animated product demonstration
I can only assume that the "microspheres" take the place of a more traditional Fresnel lens, but perform better because of how small they are compared to machined Fresnel grooves. I assume that most of the RP screens made from materials similar to this one are rigid.

Most of the big screen manufacturers have rigid screens that are supposed to perform very well in higher ambient light condition, but they are extremely expensive. check out
Dalite and
Draper
for some ideas. Unfortunately, at $8,000-$12,000 MSRP for a standard 96x72 4:3 screen (no joke), they are pretty far out of my price range. I can only assume that they become much, much cheaper when mass produced (for things like DLP TVs)

I currently have a commercial XGA front projection system (Optoma 757) but I would like to be able to use what I have with more ambient light. At first it seemed like RP was the ideal answer; but I really want to keep my current large screen size (106" horizontal) and the really good screens (the ones that reject a lot of ambient light) are just too insanely expensive for me to even think about.

In the meantime, jmrguy's success so far (congrats!) has got me thinking about trying to put together a 17" 1280x1024 PJ to try out in my current FP config. I think that something like this driven with HDMI 720p (or 1080i through a nice motion adaptive line doubler/scaler like the VP30) would look awesome.

-john