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Discussion Starter · #1 ·
I have spent the last month building a screen for my 7205 projector. My previous screen was a piece of cotton fabric from Walmart stretched over a light wood frame. I figured the walmart fabric at not much more than 0.5 gain, since the image was about the same brightness on the reverse side as the front side.


I bought a paint sprayer (HVLP) just for this job. I built the screen out of two sheets of 3/16 inch plywood. I cut two pieces 54 inches long and assembled them into a 98 by 54 inch screen. Then I gave the whole thing a skim coat of patching plaster.


I put four coats (very thin coats, about 10 ounces per coat) of primer, followed by four coats of SM. I machine sanded each coat with 220 sandpaper.


finally, four coats of MM (1:1:1 with an ounce of SM). No sanding on the last two coats. The surface is like fine white sandpaper. Very uniform. I sprayed across the eight foot width, then I went over the whole surface again, this time across the 54 inch dimension. I moved fast enough that the coats were quite light.


The finished product is very even, and feels a little finer than the 220 sandpaper.


But now the disappointment. The screen is just a tiny bit brighter than my old sheet, and it's more noticably brighter in the darks than it is in the whites. If I were to walk in the room with a movie in progress, I certainly couldn't tell which screen it was being projected on.


BUT, there is one plus: I do get a slightly more watchable image with the room lights on (but I never watch movies that way, however)


If you have complete light control, does the screen material make any difference?


By the way, the cotton fabric I got was a polished cotton, that more closely resembles silk. Also, I had always thought it was white, but when I compared it to the MM screen, the fabric had a definite silver tint to it.


I really expected the image of the MM screen to be much brighter. could it be that "twice as bright" is actually barely discernable?


I'm not unhappy with the screen. It yields an excellent picture. Absolutely no hotspotting or non-uniformity. And it looks much more professional than a piece of cloth stuck on a frame with thumb tacks.


I have no measuring equipment, but the cloth seems to yield more contrast than the MM. (although only a very slight improvement which can only be seen when the two screens are side by side in a dark room) And as I said, with the room lights on (I have no dimmer), the picture is noticably better with the MM screen.


since I didn't sand the last two coats, does anyone think a very light sanding would improve the screen any? With a 7205, the image is fine except for some very dark movies, where I wish it were a little brighter. (I'm not running in bright mode, as that lowers the contrast)
 

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tshirk


MM the MMud is not being marketed as a bright screen anymore !! IT seems like MM has proclaimed the mix as being a CR boosting screen with excellent ambient light qualities now .


If you sand the final coat even slightly it will dull the finish even more and you will have less gain than you do now.


tshirk did you have to buy a compressor as well with your hvlp rig ?


Bruce
 

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Sanding won't make it brighter. Turning your pj on bright mode will. MM with SM mixed in darkens the picture slightly. The SM beneath the MM provides the potential of darkening it ever so slightly more. You'll need more lumens for the screen you've made to get a brighter picture.


If not satisfied as is, you may be looking at painting over what you've just completed. If doing this, then yes sand over your last coat before resuming your next coat.
 

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DIY Granddad (w/help)
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What 1Time says is correct. A SM/MMud application has never been touted as a Bright Screen approach, but rather one that deepens colors and contrast via a paint only method. It originally was developed to use with "light cannons" that had poor contrast ratios, but the lumens to punch light through and onto the SM,


Thin or not, 4 coats could still be too much paint. The criteria for judgement is to apply paint only until you can just barely no longer see any trace of the SM coming through, resulting in a white enough surface to reflect a good image, yet a thin enough one to allow the SM to be of some help.


The amount of paint applied my be "thin", but for sure, one thing you did wrong was to add SM to the MMud. That's redundant when applying MMud over a pure SM base, and would only serve to further attenuate the light you want to reach the SM.


What Bruce can says doen't count for much.
 

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Discussion Starter · #5 ·
Well, I sanded just a small corner of the screen. It now has the feel of a plastic laminate, and no longer feels like sandpaper. Strangly, I can't really see any difference. Again, I am not unhappy with the screen. I'm not going back to the cotton. I just thought it would be a lot punchier than a piece of cloth I bought at Walmart.


And yes, I bought a compressor for the sprayer, but it's not a big one. 17 gallons and 8 CFM at 40 psi. I thinned the paint more than recommended I'm sure (about 30 percent), It took three coats to get to the point where I could no longer make out the SM. The last coat was sprayed on from a greater distance to give the rougher texture, and was very light.


It looks much better than my old one. And even if it's just 1.0 gain, I would have thought it would be noticably brighter.
 

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Here's another option. Finish sanding the whole thing and then apply mission313's mixture: 1 part white opal perlescent + 1 part deep base + 1 part crystal clear polyeurethane matte. Although 2 or 3 sprayed coats should increase the gain and brighten it up for you, I can't guarantee anything since I haven't tried it.
 

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tshirk, we have a GESSO (artist's white canvas primer ) here in Australia that contains MICA (PEARLESCENT PARTICLES)...about 15% according to the company that makes it.

Compared to a good quality flat white latex house paint, the GESSO is noticeably brighter....I estimate 1.2 gain. I have mixed in 20% pearlescent paint in to ordinary flat white latex and have had similar results in gain to the gesso.

You could easily go over what you have with the above simple mix.
 

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I did a test panel of 2 parts UPW + 1 part *** a while back and did not find any increase in gain over straight UPW; however my test panels were fairly small.


I'm not suggesting a mix of *** and a flat latex won't show an increase in gain when used on a full screen. However, it makes more sense to me that mission313's mix would stand a better chance of yielding the desired results, given that successive coats would provide an incremental increase in gain.
 

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1 Time, *** has a sparse population of reflective particles. You would need something like a pearlescent ''MEDIUM'' which is thick and full of MICA.
 

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A quick note:


After having sprayed two coats on a 122" diagonal LF screen using a 2 Oz SM in MMud mix, I preceeded to roll my Nissan 3 times with both that paint and my Compressor aboard. The balance of that particular mix became a wonderful coating across the back and side of the Nissan. Since the application was an important one, and I did not want to risk creating a replacement mix that was any darker, I opted instead to make the final overlay significantly lighter in the SM department. Today will be the first time I plug up a PJ (50-HD @ 1000 lumens) to check out the image quality.


This is that screen;
http://img.photobucket.com/albums/v4...ngFarmerHT.jpg


I expect good results. If they are forthcoming, you would be best advised to apply the same strategy. Just sand down your top coat until it's really smooth. Texture will refract light and lessen your preceived brightness. I'd save drastic action such as sanding everything down and re-doing your screen toward another application until you try to mitigate the fact that you used both SM as a base, and a MMud-SE mix as a top coat.


To my recollection, Mission 313 was less than completely happy with his final evaluation. I might be wrong however, so post him a PM and stand ready to try that if you desire.
 

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tshirk

After reading your last post and if you indeed have a lot of texture then you should manage to brighten up your screen somewhat by a CONSISTENT very light sanding with at least a 220 grit paper carefull to not over or undersand any one area .


I always thought that the 7205 was a bright projector and didn't need any extra screen gain or punch, even in cinema mode .


MM would you say that you could roll an american car and get the same results ? and next time for the sake of experimening would you be willing to roll six times to see if it improves the mix .


Bruce
 

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Quote:
Originally Posted by ziggyr
1 Time, *** has a sparse population of reflective particles. You would need something like a pearlescent ''MEDIUM'' which is thick and full of MICA.
I assume this is your explanation for why I saw no gain with a 2:1 mix of UPW and ***. If so, no problem. However, mission313's mix uses *** and it's reduced MICA seems like it would be preferred over a higher concentration. In any event, *** is the only somewhat white pearlescent I've found at Home Depot or Lowe's. If there's something better here in the U.S., I'd like to know. Thanks
 

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Check out the art supply stores in your area. there are many brands of pearlescent paints available....especially in small tubes and bottles.

Another idea is to thin out the UPW with some clear matt acrylic and then adding in some ***. Better to mix small test samples until you have something that has gain without hotspotting. Somewhere in the mix ratio will be the acceptable performance factor for a white looking paint that has a bit of punch.
 

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I've still got plenty of *** to play around with for now, but thanks for the idea of checking out some local art stores. There very well should be a better and perhaps whiter perlescent out there.


What you're suggesting with the UPW, CCPM and *** certainly makes sense, no doubt. However, from what I recall from mission313's experiments was UPW covers so well it takes too much *** or VPG or whatever to see the gain without the whole mix color shifting too much. I could be wrong on that but for now I'm more inclined to build on his one proclaimed success than to go back and try to rework what I believe he's already tried and failed.


Anyway, I just wanted to suggest to the thread starter a proclaimed successful way to add gain.


I actually can't wait to get back to mixing up some paint to see what I can come up with. I have a few ideas and just might have a thing or two... but not yet.
 

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tshirk,


I believe part of your low gain comes from sanding the SM. I recall reading that sanding this paint will reduce it's reflective properties and make it more akin to a gray undercoat than silver. Just a thought.


kevtherev
 

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I was happy with the final 313 mix top coat (1 part DB - 1 part *** - 1 Part CCPM) as a way to add gain "if" you are willing to make compromises in other areas such viewing cone and contrast on low contrast projectors (sub 500:1) However that can be reduced by using shades of gray as your base coat. Of course application was always my biggest problem as with any paint solution. I am just very picky and like the sprayed versions. In my opinion, if you want a really high gain screen in 3+ range the original 313WHITE with VPG will get you there if you can spray it as a matter of fact I compaired it to several PRO screens and it was very similar even with the color shift. ;) I did a whole lot of experiments with over 150 mixes and variations of paints, coatings, films,Vinyl, etc. I still say my favorite off the shelf solution is KILZ2 without a doubt. If I want more gain I just spray on 2 coats of the 313MIX and it looks pretty good for my CRT.


I found that the addition of *** to UPW is a futile exercise though you can get a VERY slight gain (maybe a ".1") in a mix containing Deep Base for example 1:1:1 MMud the more translucet the more gain from the ***. I found it took up to a 6:1 or more ratio of *** to get any real gain, but you will begin to get a warm color shift in ratio 's that high as well as sheen and artifact issues. If I were making a LF screen I would try thined 2 part DB - 1 part UPW mix based on my tests which once cured would give you a nice non-color shifted flat finish with similar amount of translucency. However many people like the warm tone color shift of the ***. Especially for older PJ's.


I have tried alot of formulas which had great results but every combo has its trade offs. Someday I will combine a list. My absolute best results came from using a 3M/avery Films lamenated, just rather cost ineffective. I don't remeber the exact products so don't PM me please. :)


Best Regards
 

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Discussion Starter · #17 ·
My screen is in my home theater on the third floor of my house. I painted it on the second floor of my garage. it was a job getting it out of the garage and into the home theater. So it's going to stay where it is. I'm enjoying it (and the 7205) very much.


One thought (or question) Is the benefit of having a "rough" texture to eliminate hotspotting, and does it change the gain of the screen. I have no measuring equipment, but I can't see any gain difference.
 

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Quote:
Originally Posted by tshirk
One thought (or question) Is the benefit of having a "rough" texture to eliminate hotspotting, and does it change the gain of the screen. I have no measuring equipment, but I can't see any gain difference.
The benefit of "rough" might indeed reduce hotspotting, but at the cost of overall luminosity. Your turning down the entire light output to prevent a "warm spot" in the middle of the screen. Thats pretty drastic engineering.


The better way to go would always be as reflective and "Smooth" as screen as possible that maintained the highest degree of reflectivity possible without creating the Hot spot.


This has been debated for quite a while, but usually, the ONLY reason someone has "roughness" to deal with is due to some degree of trouble laying down a smooth coat. I really cannot remember anyone purposely introducing a rough texture just to help mitigate or reduce too much reflectivity. To many other things suffer as well.


Go Flat, Smooth, and Textureless, in a shade of mix that does not work against your PJs attributes.
 
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