Yet another solicitation for DIY screen advice (C&S?) - Home Theater Forum and Systems -

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post #1 of 6 Old 02-07-10, 02:34 AM Thread Starter
Join Date: Feb 2010
Location: Bayfield, Colorado
Posts: 11
Yet another solicitation for DIY screen advice (C&S?)


After balking at the cost of Goo and Digital Image paint, I've spent some time reading about DIY screen solutions over the last few days, both here and on avsforum. Neutral grays, Black Widow, Cream&Sugar, SilverWhatsit. I think I'm beginning to understand at least some of the issues; it seems like C&S might be a good solution for me, but I have a question or three.

The setup is

Optoma HD80 (which will have a new bulb as of tomorrow (we've been watching this on a textured beige wall (with two electrical outlets that usually appear in the black letterbox band on the bottom during 2.35:1 etc movies) for over a year and loving it, but its time to "kick it up a notch; the outlets have been moved, the texture was knocked down with a surform plane then skimmed with drywall mud and sanded. Two coats of Kilz2 go on as soon as I get back home. Maybe that will be the end of it, but I feel compelled to 'try for more').

Ceiling mount 20'10" from wall (near maximum keystone adjustment due to large beam in the way)

Projected image ~135x75 (~155 diagonal) from a PS3

Seats usually about 15 feet from screen, seated no more than 6-7 feet off projector-to-screen axis, so probably less than 25 degrees off center in the horizontal plane. Viewing eyeball height probably 40"? Projector lens about 84" off ground?

Usage is 75% movies, 20% video games in the dark, 5% Wii fit with dim lights.

Light control (not counting light off the screen) is excellent most of the time (multi use basement, heavy blackout curtains, mostly use at night). Room walls, floor, and ceiling are mostly off-white, though we may change this, at least in the vicinity of the screen. Not a rental; I can pretty much do whatever the boss^h^h^h^hwife lets me get away with. Room is probably close to 40' deep, 20ish feet wide, but irregularly shaped.

If I'm using the calculators appropriately, I'm down around 9 fL intensity. Seems like a screen with a little gain might be of benefit (around 1.4?). We *Like* the big screen, so I'd like to see what I can do to boost the intensity before I back off on the zoom.

Obviously things are washed out when doing Wii fit even with subdued lighting. It would be nice if it were better, but not worth sacrificing much for. Movies have been wonderful, but I think I may be starting to get more critical. I think I first noticed a problem playing MotorStorm Pacific Rift; couldn't see where on earth I was going half the time in 4-way split screen -- seems to be a contrast problem. The kids trounce me, so it may be poor contrast discrimination in my old, surgerized eyeballs.

Hopefully that's an appropriate amount of background... The actual questions are:

Has anyone ever gotten around to measuring gain on C&S? I'm guessing its less than 1, but not much...

Any measured gains on other color neutral, non hot-spotting DIY formulations that might be in the 1.4 range?

Does it make any sense to blow the $$$ on Goo or DI when viewing this far off the (vertical) axis? (is the 1.8 gain on those measured? any idea what the 'cone of darkness' is on those?)

Any other words of advice on a DIY paint-on-wall screen?

If you managed to read this far, thanks, and I look forward to Words from the Wise.

fnordmorph is offline  
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post #2 of 6 Old 02-07-10, 10:32 AM
Join Date: Dec 2009
Location: Indiana
Posts: 53
Re: Yet another solicitation for DIY screen advice (C&S?)

You can search some threads on CS here and get the info, but I believe that CS is 1.0 gain. I just did CS on my system and love it compared to my friend's CRT Goo screen, especially since mine cost a fraction of the Goo.

One thing you didn't mention is whether you have calibrated your projector with a good video setup disc. Using a good setup rather than adjusting by eye can really help get the contrast and brightness best for all scene types. I bought Digital Video Essentials for bluray off of Amazon for less than $20 and it was well worth the investment
CasePro is offline  
post #3 of 6 Old 02-07-10, 12:02 PM
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Join Date: Oct 2007
Location: Central PA
Posts: 3,772
Re: Yet another solicitation for DIY screen advice (C&S?)

Hi Dan, welcome to HTS!

Very informative first post.

The best way to the fight the deleterious effects of ambient light on projected image quality is to use either a brighter PJ or a darker gray screen. In your case going with a darker gray screen probably isn't an option because of the limited amount of lumens available from your PJ at your desired screen size.

Using the data from the projectorcentral review of your PJ, with a 155" diagonal screen you are getting anywhere from almost 10 fL. down to just below 7 fL. of illumination depending on video mode and lamp power setting. These figures don't leave much room for lamp dimming due to usage before your image would drop below what most would feel to be tolerable brightness levels; this however is a subjective thing.

Of the mixes we recommend, Cream&Sugar™ does seem to fit the bill best for your needs, but keep in mind that it isn't much of an ambient light performer. It's better than a white screen, but still loses image contrast if much ambient light is present. It is however a screen mix that is inexpensive and easy to mix and apply. After you prime your wall with Kilz2 project on that surface for awhile and see how you like it. C&S™ will provide an image of about the same brightness while giving a small boost to image contrast since it is physically darker than Kilz2.

The peak gain of C&S™ is something like 0.98, but we can safely round that up to 1.0, and there is no perceptible viewing cone.

So far we have concentrated on making screen mixes designed for wide viewing conditions, but it seems that there is a need for screens with a more limited viewing cone, we will have to work on that. It's relatively simple to raise the gain of a mix by simply making it glossier, but the problem is that it doesn't take much added gloss to also produce visible hot spotting.

Below is an example of hot spotting that would drive me nuts. This is a very expensive commercial screen (Stewart FireHawk G3), but you can see a very visible brightness difference between the center of the screen and the edges. It is most visible in the white uniforms, but it is even visible in the green grass.

Screen gain is a zero-sum game meaning that if a screen has a gain over 1.0 for a viewer on-axis it will have a gain of less than 1.0 for a viewer off-axis. The higher the peak gain of the screen the greater disparity between on-axis and off-axis viewing angles. When this disparity grows large enough even a single viewer will see a brightness difference, which is hot spotting.

We can't recommend the use of Screen Goo paints since they are not color neutral and their stated gain is way less than their measured gain. Our review of the Goo mixes is here.

I am unaware of any screen mix of 1.4 gain that doesn't hot spot.
Harpmaker is offline  
post #4 of 6 Old 02-07-10, 10:50 PM Thread Starter
Join Date: Feb 2010
Location: Bayfield, Colorado
Posts: 11
Re: Yet another solicitation for DIY screen advice (C&S?)

Thanks for the replies; confirmed what I already suspected. The main reason I asked was my constant wondering if I missed the all important 'mother thread' in my readings. Finally home, bought Michael's silver sparkly stuff on the way, put new bulb in projector and watched part of 5th element BD on the non-uniform drywall mud skim coat. No longer all that worried about brightness. Prime tomorrow and watch for a while, then probably on to C&S. If I can dig my way through the snow to the paint store.

Thanks to all those who provide data beyond eye candy screen shots. Nice to have folks around who have the ability and the gumption to do the data gathering part of things.

Maybe MythBusters should do a projector screen segment... ?
fnordmorph is offline  
post #5 of 6 Old 02-07-10, 11:54 PM
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Re: Yet another solicitation for DIY screen advice (C&S?)

fnordmorph wrote: View Post
Maybe MythBusters should do a projector screen segment... ?
Oh be still my beating heart!!! What an episode that would be!

Good luck on your screen Dan!
Harpmaker is offline  
post #6 of 6 Old 04-29-10, 03:50 PM
Join Date: Apr 2010
Location: Yorkshire
Posts: 5
Re: Yet another solicitation for DIY screen advice (C&S?)

I've just painted my wall, this is some good advice to follow. Lots to consider!
Don72 is offline  


(c&s?) , advice , screen , solicitation

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