Film-Tech Forum ARCHIVE: About MDI mirco-perf distance/resolution

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Posted by Frank Angel (Member # 248) on 09-14-2017, 11:59 AM:

We are contemplating putting an MDI silver screen w/microperfs in a small screening room. Does anyone who is familiar with this screen know how far away a viewer needs to be -- in other words, what's the closest distance to the screen where the perfs would still be visible? Seats will be as close as 10 feet. Does Strong have a recommended minimal viewing distance to the screen?

Thanks

Posted by Steve Guttag (Member # 268) on 09-14-2017, 12:15 PM:

What I recommend is having them send you a swatch of the material with the perfs. Then you can tape it up and decides for yourself when the perfs become invisible to the naked eye.

Posted by Jim Cassedy (Member # 4115) on 09-14-2017, 12:27 PM:

I don't have any personal knowledge or specs on the "mdi" screens,
but in a general primer on screens I picked up once at a trade show
it says that if audiences are seated "within 15ft", a microperf screen
should be used. I have some sales literature here from another screen
maker which claims that its' microperfs (0.55mm) are invisible at 5ft.

(although on their specifications chart, it shows a recommended
minimum viewing distance of 6ft)

At the risk of suggesting the obvious, STRONG or your dealer would
probably be the most accurate source of this info for you.

Posted by Marcel Birgelen (Member # 6801) on 09-14-2017, 12:29 PM:

Like Steve already mentioned, it's best to have them send you some samples so you can judge for yourself. Also, if you do not have a projector in place, at least use a very bright flashlight to light it up from the front, because with only ambient light, your judgement will most likely be off.

Our screening room uses a micro-perf screen with 0.5mm perforation and about 30k holes per sq ft. and a gain of ~0.95. Most microperf screens roughly follow those specifications. At least around here, I couldn't find a reputable source for perforations smaller than 0.5mm.

Previously, we used a woven screen, but the weaves were still noticeable in the front row and were pretty annoying in bright scenes. Although woven screens are superior for sound, the micro-perf screen didn't impact the perceived sound quality in any way, but it did greatly improve the image quality.

Now, in the first row, which is about 9 feet away from the screen, you can still notice the perforations if you know what to look for in very bright scenes, on the second row, in which your head will be about 15 ft. away from the screen, the perforations are practically invisible, also during the brightest scenes.

We did have to adjust the zoom level which we used for content with an AR of 1.77, because in some rare cases at the particular zoom level and especially with 4K content, we would get some noticeable moire patterns. So, we're not using the full height for the screen now in 1.77.

Posted by Frank Angel (Member # 248) on 09-14-2017, 12:32 PM:

As always, thanks guys. Seems like we could be in the ball park. I'll see if Strong has any hard number, but having a swatch is the most reliable. Last thing I want is for the client to come back asking, "What are all those little holes I see whenever there is a picture of the sky?" [Eek!]