Projector Lens Masking for Zoom CIH? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 13 Old 03-02-2020, 02:48 PM - Thread Starter
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Projector Lens Masking for Zoom CIH?

Hello,
I am very much considering a Zoom based CIH setup in the comming weeks.

I have speakers underneath my screen (around 31 inches) and it feels good height wise for our current 100 Inch (been like this for years). I am thinking of buying a 125 screen to do CIH and would like to keep the screen height the same. I will need to mask the overspill to keep the light off the speakers.

What I am thinking (and why I am posting this thread), Is that I can simply mask the top and bottom overspill on the projector side. I figure I can hang/attach "masks" infront of the PJ and lens that masks the overspill from zoom. Think of a few metal brackets and pieces with some magents that trap the top and bottom overspill on at the projector.

Has anyone done this before?
Are there any products to buy or just DIY?

Bad idea?

Is there some other way to keep the "zoom" overspill off the Speakers?
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post #2 of 13 Old 03-02-2020, 03:03 PM
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I did pretty much the same thing for three years only I had my projector facing backwards and hitting a mirror and then reflecting to the screen. it extended my throw distance greater than the room was deep. On the mirror I had steel strips held on with two sided foam tape and then I had black plastic strips that had magnets attached I could slide and the magnets held them fixed.

There are only 2 places where the masking will be in focus perfect one is where the image is being produced and the other is the screen surface. That doesn’t mean you can’t block light it just means the edge of the mask will be a fuzzy gradient of light to dark. The projector itself will be trying to make those areas as black as possible and what I did was put the masking panel outside that self-masking line my the amount of the fuzzy edge. It masks most of the light and with what the projector was doing self-masking it worked pretty good. I was about 12=18” from the lens the closer you get to the lens the greater the fuzzy edge.

Try getting a piece of black paper and just hold it up you will see what I’m saying.

I think for what you want you will make it work.

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post #3 of 13 Old 03-02-2020, 04:08 PM - Thread Starter
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Quote:
Originally Posted by bud16415 View Post
I did pretty much the same thing for three years only I had my projector facing backwards and hitting a mirror and then reflecting to the screen. it extended my throw distance greater than the room was deep. On the mirror I had steel strips held on with two sided foam tape and then I had black plastic strips that had magnets attached I could slide and the magnets held them fixed.

There are only 2 places where the masking will be in focus perfect one is where the image is being produced and the other is the screen surface. That doesn’t mean you can’t block light it just means the edge of the mask will be a fuzzy gradient of light to dark. The projector itself will be trying to make those areas as black as possible and what I did was put the masking panel outside that self-masking line my the amount of the fuzzy edge. It masks most of the light and with what the projector was doing self-masking it worked pretty good. I was about 12=18” from the lens the closer you get to the lens the greater the fuzzy edge.

Try getting a piece of black paper and just hold it up you will see what I’m saying.

I think for what you want you will make it work.

https://www.avsforum.com/forum/110-d...tiny-room.html
Thanks Bud it makes sense.

There will a few inches of screen frame to catch a non sharp edge, I will test some things out on the current setup to see how it looks.
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post #4 of 13 Old 03-02-2020, 04:40 PM
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Quote:
Originally Posted by kemannthey View Post
Thanks Bud it makes sense.

There will a few inches of screen frame to catch a non sharp edge, I will test some things out on the current setup to see how it looks.
YW

My first projector was in a basement with a really low ceiling it was painted black about 6’ in front of the screen and white on the viewers end. The projector had some extra light that threw a plume on the white ceiling and it was really annoying. I made a little arm from a paper clip and thumb tacked it to the ceiling and taped a piece of black paper to it. Took about 2 minutes to do and it hung there for 8 years. People used to ask me what’s that?

Good luck and welcome to the world of CIH.

Bud
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post #5 of 13 Old 03-03-2020, 10:14 AM
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Quote:
Originally Posted by kemannthey View Post
Hello,
I am very much considering a Zoom based CIH setup in the comming weeks.

I have speakers underneath my screen (around 31 inches) and it feels good height wise for our current 100 Inch (been like this for years). I am thinking of buying a 125 screen to do CIH and would like to keep the screen height the same. I will need to mask the overspill to keep the light off the speakers.

What I am thinking (and why I am posting this thread), Is that I can simply mask the top and bottom overspill on the projector side. I figure I can hang/attach "masks" infront of the PJ and lens that masks the overspill from zoom. Think of a few metal brackets and pieces with some magents that trap the top and bottom overspill on at the projector.

Has anyone done this before?
Are there any products to buy or just DIY?

Bad idea?

Is there some other way to keep the "zoom" overspill off the Speakers?
What projector are you using? That can alter what you may or may not need to do.

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post #6 of 13 Old 03-03-2020, 10:32 AM - Thread Starter
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What projector are you using? That can alter what you may or may not need to do.
Not sure yet (part of the upgade planing). Epson 5040/50UB or JVC RS540 likey for budget reasons. Does JVC "Masking" fix this sort of issue?
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post #7 of 13 Old 03-03-2020, 11:33 AM
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Does JVC "Masking" fix this sort of issue?
JVC's masking feature is just a form of electronic blanking. It turns active picture into black letterbox bars. Those letterbox bars are still part of the image coming out of the projector. The projector cannot shut off those pixels or stop them from coming out of the lens.

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post #8 of 13 Old 03-04-2020, 06:16 AM - Thread Starter
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Or maybe I get a cylindrical lens? I have read some folks are using isco (and related) lens into the 4k era.


What lens can work with 4k? Isco iii and isco iiil (and related)?

I have 2.1 x throw (.95 dlp) today bet will have 4k soon. There is a small amount of horizontal lens shift now because of stairs. Is there a lens I can buy for 1080p now and work with 4k later?
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post #9 of 13 Old 03-04-2020, 08:59 AM
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Quote:
Originally Posted by Josh Z View Post
JVC's masking feature is just a form of electronic blanking. It turns active picture into black letterbox bars. Those letterbox bars are still part of the image coming out of the projector. The projector cannot shut off those pixels or stop them from coming out of the lens.
While that is true for both the Epson and JVC, both have a black floor low enough that you won't see over spill on anything but a gloss light colored wall.

I have no physical masking on the NX7 and didn't on the RS520, the electronically masked black pixels aren't visible on the wall (flat dark red) or speakers. Now something like an XPR DLP where the black floor isn't good at all, you would probably want physical masking if you were zooming for CIH.

So I don't think the OP need worry about masking with regards to top/bottom over spill on either unit. The Epson is reported to have some light spill around the lens that may make side masking for narrow content desirable. Neither of my JVCs had an issue with this, so no side masking is necessary.
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post #10 of 13 Old 03-04-2020, 10:13 AM
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The OP will only really know when he watches some really dark content and sees with his own eyes how much light bleeds thru the black and how reflective his speakers are.

The idea of self-masking or not needing masking is near and dear to me, as I don’t have any with my stealth screen wall. I don’t know about XRP DLP and a white screen, my guess like you is the shadows of black bars would be there. I do know that with dark chip 3 DLP and RGBRGB technology and a .5 gain gray screen there is almost no hint of black bars except when the over all light level of the movie drops very low.

It should be easy enough for him to rig up some kind of a hoodwink if he has a problem.

Bud
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post #11 of 13 Old 03-07-2020, 09:03 AM - Thread Starter
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I am going to test out today with a blackout cloth screen to see what is what with a temp "zoom" setup with a Sony 350es.
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post #12 of 13 Old 03-07-2020, 09:30 AM
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I have a Sony 385es and it has a "blanking" feature that does the same thing digitally. The edges are razor sharp and I can move all 4 edges independently of one another to really dial in the screen size. Not sure if the 295 or 350 offers that, but it's a great feature for zoom CIH control without manual masking. If you're in the market, that's a feature worth having.

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post #13 of 13 Old 03-08-2020, 09:45 AM - Thread Starter
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Well the test was very helpful on several fronts.


I picked up 4 yards of 54 inch tall blackout cloth for 12 and temp hung it on the theater.


Eyes to screen is around 9.5 feet and material was all 1080p. .


1. The overspill was not and issue. If you went up to the screen wall you could see faint shadows but nothing from seated position. On first pass ( 3-4 hours of 2.40 content) it looked just fine.(rooms has dark gray walls a black speakers)

2. There is more width then expected. The space supports a 10 foot wide screen. We ended on 51 high by about 123 inches. We were looking at 110-115 wide before this.

3. 1080p streaming was short on pixels. We are very used to 1080p on a 100inch 16:9 at this distance. It was clear there was just less info to go around with the zoom. I think this would work best with 4k at this seating distance.


4. Projector side masking can work if needed if the future with a larger screen boarder. As discussed there is just a few inches if fuzz and would a quick project to do for real.

5. Everyone liked it! There is a 2.40/2.35 screen in our future!
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