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Discussion Starter #1
I would like to use a Stewart microperfed screen with a Sony VW10HT, however, I am concerned about moire effects. The screen will probably be 96" wide. Can I expect moire effects to be a problem with this projector/screen combination? I have read that these problems can be reduced by either defocussing the image slightly or by using a Cygnus processing lens. Can I expect either of these methods to eliminate the moire effect? My first choice would be to use defocussing. Does the amount of defocussing required to eliminate the moire effect result in a loss of detail in the projected image?
 

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Stewart won't even sell you the Microperf if you tell them you have a 10HT. Did you try the Da-lite of the Draper?


Not sure if they have same problem of not.
 

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Discussion Starter #3
You must be kidding. That would suggest Stewart feels that the moire defects are so serious that they cannot be corrected. This is unfortunate news since I would really like to get a microperforated screen which I can keep for the long-term even though the projector I use may change. Perhaps I will have to rethink the Sony even though I can get a really good price.
 

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Discussion Starter #5
Redeby,

Thanks for the link. According to Don Stewart, the Sony and Sanyo 16:9 projectors produce moire effects with their microperf screens. He also states that this can be eliminated with the Cygnus processing lens.


This is an expensive solution for me. Can I expect similar success by defocussing the grid pattern slightly?
 

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Keep in mind that the moire problem doesn't always occur. On a large enough screen, it is generally not an issue (larger screen means larger pixels, thus they don't clash as much with the perfs). I would be careful, though. If you can avoid the microperf, or use a different projector, it might be a good idea.


Thanks!
 

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Scott,


The spacing between the holes of the Stewart Microperf just happens to be such that you get

interference effects with the spacing of the pixels in the Sony.


This can be ameliorated somewhat by defocusing or using the Cygnus lens that essentially does the

same thing. However, if you want a nice sharp picture - you're not going to get it with the

Sony 10HT / Stewart Microperf combo.


You really should consider a substitute for one or the other.


Greg
 

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You guys are bumming me out. I would like to use a digital projector for ease of use/brightness concerns and a perforated screen to optimise the realism of movies, however, it would seem that the combination of the two will result in deterioration of video quality.


Is anybody using a digital projector/acoustical screen combination, and if so, what is it and how do you find the synergy between the two?
 

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Discussion Starter #9
If I give up on the idea of an acoustical screen, would a calibrated Sony VW10HT/Stewart Grayhawk (54"x96") screen combination work well together? In a room with total light control do you think the image would be bright with Cinema Black on?
 

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I'm sure that using a perf screen is not a good idea in many HT configurations. I have made a comparison at a local HT store (the projector was a Sharp 9000) and I have two comments. First, I noticed no moire whatsoever (I'm not sure whether the Cygnus lens was present, but they do sell that product). Secondly, there was a distinct and objectionable high frequency rolloff when the screen was lowered.


The dealer admitted to this but claimed that most people never notice the effect. He also said that Stewart includes special equalization networks with the perfed screens to overcome this loss, but he could not install such with the particular surround receiver in that demo room.


The root cause of the problem is the perfs for HT screens are very much smaller than those in commercial theaters, and the high frequency attenuation is therefore greater.


If you are using seperate processor and audio power amps, I guess this is less of a problem, because you could use the equalization networks. Alternatively, you could conceal the speakers behind acousticly transparent panels above or beneath the screen, and make use of the fact that human directional hearing is virtually all in the horizontal plane.


What I did was conceal the three front speakers and subwoofer in cabinetry underneath the screen, and used cabinet doors where the panels were replaced with speaker cloth grilles. Then I removed the grilles from the speakers themselves and the result was balanced sound with the dialogue effectively anchored to the screen. The only problem I had to overcome was a few cabinet rattles from the subwoofer, easily fixed with some extra screws and some stick-on felt pads.


Gary
 

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Scott:

http://www.thebigpicturedvd.com/cgi-...conf=DCConfID2

http://www.thebigpicturedvd.com/cgi-...conf=DCConfID1


These are links to a VW10 forum and the other to a Stewart filmscreens forum. There is a search option where you can search the forum and archives for relevant topics.


I just got an idea (it might not be cheap though and may turn out not so good). If your purpose with the perforated screen is to get the center sound a bit more vertically centered why not use the center pre out, connect it to a mono amp and have a second center speaker above the screen. I believe this would create a phantom center channel in the center of the screen.


/H-B
 

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Discussion Starter #12
My understanding is that using dual center channel speakers with one above and one below a screen will result in serious lobing effects. The problem is that both center channel speakers receive the same signal which will tend to cancel out when they meet.
 

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Dear Scott,

Stewart does not recommend a THX Micoperf screen

when used with the Sony HT10, Sony HT11 or the Sanyo PLV 60. These particular LCD projector models can have moire artifacts when used with a perforated screen less than 120" wide. If one of the above projectors is used with a perforated screen, then an IMX processor would be required to remedy the problem.

When one calls Stewart Filmscreen and informs our people that they want to mix a microperf screen with certain LCD projectors, we fill its our moral duty to explain to the customer of the possible problem that they may encounter.

We have only had this problem with a few LCD projector models. Problems with DLP and DILA projectors have been almost nonexistent. This is due to the pronounced pixel fill factor that you find with LCD projectors

Regards,

Don
 

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Discussion Starter #14
Don,

In your experience could I expect an IMX processor to eliminate the moire artifacts or simply reduce it?


It looks like I will have to pass on the Sony or try to get an IMX processor cheap.
 

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Quote:
Originally posted by Scott B
Don,

In your experience could I expect an IMX processor to eliminate the moire artifacts or simply reduce it?


It looks like I will have to pass on the Sony or try to get an IMX processor cheap.
Dear Scott,

With the IMX processor properly set up it will reduce the moire by 99 percent. This subjective

99 percent improvement has been reported to us by actual Home Theater users with the Sony HT10

and Microperf combination. In our own testing we found this to be true. The last one percent of moire can be eliminated by a very slight defocusing of the image . The slight defocusing can not be perceived at normal viewing distance.

Regards,

Don
 

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I just found out that with the Sharp 9000U, for a 12 foot throw distance, the screen cannot be greater than 84" diag, which means a 73" width for 16:9. How bad will the moire effects be on a microperf screen with the 9000U? I have to have a perf screen, and I cannot change the throw distance. Should I just forget about it and wait until the next technology comes around the corner?:confused:
 
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