[calibos]

I've been flip flopping between thoughts of a professional fixed screen or DIY route, motorised masking or manual, DIY frame but pro screen material, DIY frame and blackout cloth, ScreenGoo on the freshly skimmed walls with DIY borders, DIY paint mix on freshly skimmed walls with DIY borders......blah blah blah

At least I have finally settled on how I will achieve side masking on a 110" wide 2.35:1 CIH . Velvet/Flocking paper covered window shutters in effect. Hinged at side of screen frame. Manually swung over screen or away. Professional masking solutions are bonkers prices and I just don't have the time or patience to build a DIY solution.

But that still leaves the screen.

Some things to consider. I will ultimately be using the screen with a Panasonic AE4000 or AE5000. Will use my AE900 till next year till I found out if the next gen PJ's are 3D capable.

I'll be using the zoom method for CIH. Lightcontrolled room for movies with South facing Velux.

I was thinking the kind of gain I need might narrow down the screen choice for me.

Am I correct in assuming that the recommended FL (Foot Lamberts) range is 12-22FL. Unfortunately the AE900 hasn't been used in about 2 years as we moved and had nowhere to set it up till now. When I set it up for testing the other day, I was blown away at how we had all gotten so used to plasma tv brightness and how dim the projector looked in comparison. There was only a few hundred hours on the bulb. Thus I guess I should be aiming for the higher end of the FL range. ie. 16FL+

The ProjectorCentral calc for a 2.35 screen 110" wide at my throw distance and zzom level indicates the AE4000 produces a FL of 14 with the gain set to 1.0

So I certainly don't want a surface with a negative gain. Does that rule out any of the screen options I outlined above. I guess I should be aiming for a screen gain of 1.2-1.4. Does that make my decision easier?

What are the disadvantages of higher gain? Hotspotting, Brightness drop off? Does one measure viewing angle from the seating positions to the centre of the screen? If thats the case then with the room being little wider than the screen and the seating being an L shaped couch, most views will be On-Axis and the odd time there might be viewers on the L of the couch along the side wall off axis by about 30º.

Do contrast levels go to pot with a 1.2-1.4 gain screen?

If I go the professional screen route, who makes fixed screens with wrinkle free 1.2-1.4 gain material made to order(unless standard sizes match my preferred size closely) so I can maximise screen size for the room. Any idea of pricing for a 2.35 110"x46" +119"diag of the above spec. Prices seem to be hard to find on any of the screen maker websites. Why is that?

Thanks in advance for any advice guys.

[Harpmaker]

Hi Keith,

I'll try to answer a few of your questions, or at least give you my take on them.

First off, all direct-view TV's (CRT, LCD, Plasma) are emissive devices; they emit light, and their light output tends to be brighter than most reflective projector screens. Some DIY and commercial screen paints claim to provide plasma-like images, but such is rarely the case unless a very powerful PJ is being used. A good home PJ system should give you a similar image to what you see in a commercial movie theater (which for a person setting in the center-aisle seat halfway between front and rear seats should be 16 fL. IIRC).

How bright you need your screen to be is a very subjective thing. I am very happy with a screen illumination of 10-12 fL. and a screen gain of around .9 (Black Widow), but others consider this too dark.

As a general rule, the only reason one needs a gray screen is to either fight ambient light while viewing or to increase perceived image contrast. The more ambient light you have hitting the screen while viewing, or the more added contrast you need to get black blacks, the darker gray your screen should be. Some commercial screens and DIY screen mixes have reflective elements added to help increase white-levels above what a regular gray screen of a given shade would provide. In that, they do have a positive gain, but their gain is still a bit less than 1.0.

Screen gain is a very confusing subject since it is a relative measurement. I am familiar with the Black Widow screen mix so I will use it as an example. BW has a gain of around .9 relative to a "Unity Screen" (which has a gain of 1.0 and is a perfect diffuse reflector so it has no viewing angle or viewing cone - this screen usually isn't a screen at all, but rather a block of refractory metallic oxide or Teflon).

BW reflects about 90% of the image brightness that a Unity Screen would, thus if has negative gain relative to the Unity Screen (which is the standard industry test for gain) , but the shade of gray of a BW screen is around N7.5 on the Munsell Value scale (0 is pure black and 10 pure white). If our Unity Screen was the same shade of gray as BW it would be reflecting only about 48% of the light striking it, so relative to a perfectly diffusive screen the same shade as BW, BW has quite a bit of positive gain. Regular flat/matte paint is very close to a perfectly diffuse surface.

Since gain is relative to a white diffuse surface, any screen that has gain higher than 1.0 will have a viewing cone (which is the viewing angle times two), this is simply physics. I have data for Stewart commercial screens handy so I will use it.

I tried embedding gain charts for the screens below, but they didn't work so I gave links to them instead.

The StudioTek 100
STEWART FILMSCREEN - STUDIOTEK 100
is a white screen and has a gain of 1.0 and no viewing cone or viewing angle (also called the half-angle since it is the viewing angle at which the screen loses half of it's brightness).

Their StudioTek 130
STEWART FILMSCREEN - STUDIOTEK 130 G3
screen is a white screen with a gain of 1.3 with a viewing angle/half-angle of 68 degrees. This is a wide angle and most people don't see much brightness lose in normal home theater settings, but the screen does lose brightness the further one moves their viewing position off-axis from the PJ.

Stewart also has a UltraMatte 150
STEWART FILMSCREEN - ULTRAMATTE 150
screen that appears to be the same material as the StudioTek 130, but the reflective coating is applied heavier so it has more gain, which is 1.5. This screen has a reported half-angle of 63 degrees and the gain curve is still quite linear.

Their UltraMatte 200
STEWART FILMSCREEN - ULTRAMATTE 200
screen has still more of the reflective coating applied to it and has a gain of 2.0, but the half-angle is now reduced to only 24 degrees and you can see from the gain curve that the gain lose is not linear and most of it occurs rapidly.

Screen gain is much like the clock speed of computer CPU's in that it is only one performance specification for the product, and not necessarily the most important one. Depending on how the gain is obtained, the viewing cone can drop rapidly with gains over 1.3 with a white screen, and even more if gray screens start to be reported as having gains above 1.0.

The dangers of high-gain screens are reduced viewing angles and potential hot-spotting.

Viewing angle is determined by positioning the screen sample so that the light meter (on-axis) is at it's highest reading and then moving the light meter to the left or right on the horizontal axis. The angle at which the light meters reading is one half of the on-axis value is the half-angle.

As far as I know, or have read, the gain of a screen has nothing to do with the image contrast of the projected image. This is a product of a combination of factors; primarily the native contrast of the PJ, the amount of ambient light hitting the screen (which can even be light reflected back onto the screen by walls and ceiling in a totally dark room), and the gray shade of the screen.

Sorry folks, I didn't mean to write a book.

[calibos]

Never appologise for a big post! That post was a prime example of why hobby forums and their members are a special breed of people. You don't know me from adam but you still gave me a half hour of your day and the benefit of your knowledge with that amazing comprehensive answer. Thank you so much.

Since posting my question last night I have done another bout of research and talking myself into and back out of all the options in the again

Talkin' myself into going the DIY framing and painting route and then back out of it again by worrying about streaking my roller strokes and having visible lines etc

I'm not as worried about the need for positive gain as I was last night. I had another of my Homer Simpson DOH! moments when I remembered that the FL would go up when the future AE4000/5000 was zoomed back down to 16:9 on the CIH screen. 14-15fl I got for the AE400 on the PrC calc was for 110" wide 2.35:1. The 16:9 portion of that screen will actually be the same secreen size area as my only 16:9 CIW screen. ie 80x45. Input thos into the calc and the AE4000 delivers 22FL !! So for most of my viewing which will be 16:9, if anything I'll have too much FL I also input my AE900 in. It gives 15FL for an 80x45 screen area. So the AE4000/5000 will be much brighter. For 110" 2.35:1 it gives 10FL. So theres the dramatic difference I saw between plasma and PJ. It won't be a problem because I don't intend to use the AE900 for long in the new setup. Like I said....DOH!!

However, lets talk about grey. My room will be light controlled with blackout blinds on the Velux. The carpet will be a reasonable long pile beige, walls will be a light brown/tan cappuchino colour. Ceilings will be white. The screen wall will be black with speaker cloth stretched over frames 1 ft all around screen. Screen is width of room Side walls will be masked by the folded back 16:9 masks. The sloping white ceiling will be quite close to the screen however. So I am guessing I should think about a grey screen to help with reflections and black level seeing as I am no longer worried about gain.

This kind of brings me back to the DIY or Pro route. The Da-Lite Cinema Contour with HCCV screen surface sounds interesting. Grey but with a gain of 1.1 I found pricing which isn't as bad as I thought. Its just that I am worried about the stretching of fabric and frame building if I go the DIY route. So many times I have taken on projects that were described as or I thought were easy peasy, only to find my skills lacking and where I regretted not saving the time and effort in trying to DIY and just handing out the $$$

[Harpmaker]

Light brown/tan walls can still reflect a good amount of light from the screen back to the screen, and a white ceiling (especially one that is close to the screen) most certainly will. The brighter the image the more light will be reflected back as well.

If you can't do something about that white ceiling, at least close to the screen, then I think I would recommend a gray screen for you. If you can't paint the ceiling you might think about putting some of that speaker cloth on it, at least for the last 4 feet or so leading to the screen.

Whether you go commercial or DIY is a personal choice based on your abilities and desires. I get a real kick out of doing it myself, but if you are actually building a frame and painting some form of substrate rather than just a wall, expenses can add up rapidly so there is less of a cost difference between DIY and commercial.

BWUK is one answer for DIY, and the Da-Lite HCCV is a good screen on the commercial side; it is one of the few commercial screens that is truly neutral in color so the image your PJ throws at the screen is the one you actually see!

I'm still not sure of how links to other forums are tolerated here so I'm putting this link at the bottom of the post so it will be easy for a moderator to remove if deemed inappropriate. It is to an in-depth review Mech did of some of the Da-Lite screens including the HCCV.
Da-Lite Screen Material Review - Home Theater Systems - Electronics and Forum - HomeTheaterShack

[calibos]

Okey Dokey. I've just done some more work on my google sketchup of the room and created a little animation to give an idea of the layout and the limitations being put on my screen. You'll see why I am going for CIH instead of CIW. You'll see the speaker cloth covered frame where my mains, centre and sub will be. You'll see the hinged side masks which will swing into and out of position.

I can't (SWMBO) paint the ceilings nor walls black 4ft out from the screen. With the screen so close to the ceiling there is no point painting/covering the whole screen wall black because most of the reflection will be from the ceiling anyway. I't be wasted effort and the triangular screen wall totally in black would look odd. Might as well just frame it in black just enough to absorb the zoomed black bars.

So I guess a grey screen is the best I can do.

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[martin purnell]

Hi Calibos,
Whilst our lounge is a different shape to your excellent graphics, the colour scheme and carpet is similar!
I have gone down the BWuk version with a homemade fixed frame screen.
Please check this thread for more info which will save me having to re-type ...DIY Screen Paint - Black Widow or Dulux Grey Steel 2.
I am very pleased with the Black Widow UK version and can strongly recommend it. I know this is subjective but it really does work!
Should you have any queries, please contact me.
Kind regards,

Martin