Need help with low lumens pj screen

You state above that you have what you consider a Low Lumen PJ. You also state that you have no "Light Control" issues. I strongly suggest that you use a bright Flat White Paint top coated with a Clear Matte Poly. Tiddler's graphs has shown that such a combo produces extra gain without hot spotting. Too much (hardly any amount) of Gray introduced into the equation without the addition of Pearls and Silvers (metallics) added will attenuate your image, and it seems you don't want that to happen.

But sometimes trade offs are required. If your PJ has poor Contrast performance (under 2000:1) and you want deeper Black levels and more "Color PoP" then the addition of a "small" amount of neutra Gray, overcoated with Poly, will at least be more than an acceptable choice.

With that size screen you should be in the 12 Foot Lambert range. And with light control should get a respectable image off the white screen MM mentioned above. I'm assuming you have already tried the white BOC that you mentioned or have projected to a white wall and that's how you based your screen size.

You might have trouble finding the very flat poly to use as a top coating to get just a little more help and the type poly you may find over there may have to much sheen if used alone as a top coat. If that's the case try blending it with some of the latex paint you used. By blending you can experiment until you find a sheen level that works best for you.

I wouldn't rule out a slight gray tint at 12 FL but I would suggest a very slight one if you want to experiment.

Pretty much in agreement with MM here

Check the Caparol brand... OffWhite 55, and Marin 30, Marin 25, Aquarell 25, Litho 30, and Lazur 50. Try a test panel with the light grays first though before painting your BOC screen.

I can convert to Pantone if you need that.

Smooth side.

Hi guys!! I've been lurking here for quite a while, finally decided to register. I've got a whopper of a challenge for you. I'm a member of a club that has a 1983-vintage Sony VPH-1020Q projector. We've been using an old 8mm movie screen.

Our clubroom has TWO GLASS-BLOCK WALLS (yup, regular photon bombs), one will be behind the screen, and completely blacked out, the other is along the long side of the room perpendicular to the screen. On the wall opposite the longest glass block wall, are two doors leading to a well-lit dining hall/cafeteria.

I know we gotta get something over those glass blocks, and I'll do that.

The VPH-1020Q is a light-trickler, at 450 peak lumens- they claim picture brightness (with a curved screen of gain 12) as more than 65fL. Contrast ratio claims to be 15,000:1. It's working beautifully, and at night looks pretty good, even with the flat fabric-on-tripod movie screen. (its designed to take a curved screen, but we've managed to get it square and converged on a flat screen)

We'll be running a 4:3 screen, 48"h x 64"w (80" diag), with the ceiling-mount projector lenses about 88" from the screen.

We're thinking about making a curved Wilsonart (about 3" curvature center-to-edge) Pearl Silver D487-90 ("crystal" { "-90"} finish. We're planning to spray it with a 'fog coat' and two finish coats of Tiddler's "2l pearl hotspot knockdown finish" (a mix of two 2oz. bottles of Folkart Metallic White Pearl to Behr matte poly #780).

are we on the right track, here, or are we completely insane ?

I wanted a gray, and it seems like some recent testing in this forum has indicated that the Pearl silver has even better performance than Fashion Gray under my low-lumens AL conditions, except it may be prone to hotspotting. (one user commented that it looked like a plasma screen)

I figured the topcoat would keep off-axis AL doing a shallow bounce, keeping reflections out of the viewing cone, as well as reducing the hotspotting that another user reported.

Hi again Tiddler- here's a little dope on the Pearl Silver- it's not available in the matte ("-60") finish. The info is from a posting by prof55

Pearl Silver LS D487-07
XYZ: 46.59 47.65 54.56
Yxy: 47.65 0.3130 0.3202
RGB: 188 182 188

Very neutral, and about the same lightness as Grayhawk.
Glossometer reading: MD and CD 13 +/- 3. (that's why the matt poly)

I use the term "fog coat" or "tack coat" to refer to a very light 'misting' of the surface with the paint (in this case the 2l mix), allowed to dry until tacky, before applying the official "first coat", to help promote adhesion.

thank you so much for taking the time to reply to a newbie-- I tried to do as much research as I could before posting.
-bob

I am the originator of the laminate thread. I didn't 'discover' laminates, but I did a lot of testing with them and got the data on them.

The PS90... it was never tested because it had too high of a surface sheen for a regular screen. The goal was to match the matte finish that commercial screens have. Specular gain came into play when people started using Fashion Grey. The lower the base color gain, and the higher the surface gain all mean higher specularity and that tends to mean hot spotting.

Now for a curved screen, it is a different animal. They are designed for higher gain/lower viewing cone. That is a much tighter screen with a lower audience sitting range, so keep that in mind when you are building this.

The people doing PS90 testing are trying new things, but I would start with a good color and surface and then bring the gain up. The PS90 thread hasn't been totally tested and verified like the laminates in the main Laminate thread... so that is still an experiment in progress. I'm not quite sure what the color breakdown is on the PS90 or what the gain would be, but my price quote was around twice the price of the matte finish general pupose lamimates... and that is getting to be quite expensive in my book for a test. If I could say with 100% certainty that it would work for you, I would recommend spending the money, but right now it's a lot of money for an unproven method. Now if you have that kind of money to spend on testing, that would be awsome... but if it doesn't suit your needs you are back at square one again.

A little more clarification on the point above,


Past PJs of all types used to produce decidedly less light at the edges of the image. That is where the term "Hot Spot" originally came from. The center of the image was always brighter than the edges. The larger the image, the worse the manifestation of the center being brighter was. That caused eyestrain, so that sitting close up to such a screen would assault your eyes far more in comparison than such would at a distance. Todays' PJs exhibit a better degree of uniformity, some upwards of over 95% across the entire projected surface.

The curvature at each end of a Torus screen is specifically meant to increase the gain lost at the edges of a particularly wide screen, such as one with a 2.35:1 aspect ratio. Such a screen does absolutely nothing additional in the "center". Torus screens were/are still popular with those using extremely low lumen PJs such as CRTs, of which most shoot 2.35:1 imagery more often than not.

The outside curves can also act like barriers against any light coming directly from each side, although that feature is usually redundant since the use of a Torus screen usually means a low lumen PJ is being employed, and a light controlled environment is present. However, one would be correct in saying that the net result of redirecting the reflection of light from each far edge into the center will increase the perceived and actual gain at the "center" of the viewing area, but not "on" the center of the screen surface itself.

The curvature does not much affect the quality of viewing from the side if one does not venture sideways to the point where they are actually looking past the curved edge. When viewed from 'normal' seating positions, seldom is the curvature so drastic that it actually distorts the image, and when such is necessary, specially produced Lenses work to offset that aberration.

Add to all the above the fact that most Torus users are people who also have Anamorphic Lenses that "increase" brightness by both using every pixel available, and concentrating the pixels into a smaller area, and any such actual gain increase achieved through such light manipulation is the end result.

Torus screens are essential needs for those who have such needs. They are not required for 99.9% of most people "today", including those with 2.35:1 CH set ups. Only when the screen size get enormous do they become really mandatory, and in such cases, they can make all the difference.

The OP's older Sony is a PJ that really should have a Torus, if for no other reason but to help deliver the best possible image.

I think you guys figured out the method behind my madness. I wanted to do a laminate screen, and with my AL issues, I figured Fashion Gray matte was the ticket. -- but I'm an inveterate "optimizer"

I ran across the experiments in the laminates thread with the Pearl Silver, available only in a "crystal finish". The few experiments done seemed to indicate it would make a pretty nice screen, except for hotspotting. Since I'm pretty much required to run a torus-section screen, I can get away with a material that otherwise might be considered too "glossy". (off-axis viewing isn't a problem-- this room is about 12 feet wide by 30 feet long, with the screen on the 'short' end at the front of the room)

Then I got real creative, and started thinking about Tiddler's 2L FolkArt Pearl/Behr matte poly mix. Maybe it would give me even more luminosity than the straight Pearl Silver- still without hotspotting.

It seems that if I'm lucky, I could get the best of all possible worlds- white looking whites, black looking blacks, a high 'pop' factor, resistance to ambient light. I'd be restricted to a narrow viewing angle, and a torus-section screen, but those were both preconditions, not sacrifices. That was the basic theory behind my selections.

I think what I'll do is order up a sheet, cut it to size, and then divide the leftovers into 2 minisheets-- I'll spray one with Tiddler's Pearlmix, leave the other plain, and see what the ^&%&&*^% happens when I project an image onto them.

I've already got the FolkArt, Behr, and Delta products, need to concentrate on building the curved ribbed frame for the screen. Maybe by then, before I commit to the $$, there will be some results posted in the laminate forum. If it all goes to hell, I can always just glue a sheet of fashion gray over the PS crystal.

Thanx guys, and any further advice is appreciated.

BTW, since we've already adjusted the PJ to work with a flat screen, we can't use the ordinary 'stick method'. Does anyone know what kind of curve this thing originally had? Since we've actually got it converged and looking square on a flat screen, I was figuring that any curve would be an improvement, and 3-4" center-to-edge would certainly be somewhere within the region of adjustment.

Thaks to all, especially MissisippiMan and Tiddler for all your pearl topcoating research-- you've inspired me.

Hi again folks--- Since my 'low lumens question' was on-topic here, I almost didn't notice that we'd strayed into a discussion of Pearl Silver Crystal. I'll move this to the New Laminate Test: Pearl Silver thread, at http://www.avsforum.com/avs-vb/showt...9&page=6&pp=30 . I'll start there with a brief summary.

It seems as though rfischer's HD order of the PScrystal got fouled up. I have a different source I'm going to try.

-bob (Uncle Scurvy)