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Positive Gain Shimmering (Cima Neve)?

Positive Gain Shimmering (Cima Neve)?
« on: May 29, 2021, 07:23:57 PM »
A few weeks ago I received my latest projector the JVC DLA-RS2000 which I ordered from Craig. I've been quite happy with it. At the same time that I ordered the projector I also ordered a Stewart Cima Neve 16:9 110" screen to replace my 110" Carada Classic Cinema White screen. The classic cinema white screens had a defect in the material that caused lines to show up on the screen some years after they were made. My 110" screen isn't the only Carada screen that I have had that this happened to so I wasn't surprised to see it happening to this one. The only positive gain screen I have had was a Carada Brilliant White and really it was closer to 1.0 gain than it was to the 1.2 gain advertised. It did not have any shimmering. Now I have my Stewart Cima Neve up and I am pretty happy with it overall. It is finer grained than the Carada screen and it has no defects in the material.

The only issue I have is shimmering when bright things are on the screen. At first I thought it might be hotspotting but I don't think it is because the position of it moves if you change seats. I have two rows of 3 chairs with the second row elevated. The projector is hanging over the back of row 1. If I sit in the money seat center of row 1 I can see the shimmering pretty much right in the middle of the screen. If there is a bright light or white screen I can see a bunch of tiny shiny spots there. If I move left one seat the shimmering is center left and if I move right the shimmering moves to center right. If I move to the back row I can't see it at all. That indicates to me that this has to do with the angle of the image projection and the heads in those seats relative to a positive gain screen. I should say that it isn't terrible but it is noticeable especially if you know it is there. I realize that the screen is not defective and that this is an issue that can occur with any positive gain screen.

The projector is mounted at about 11.5' which coincidentally is exactly as close as it can be to that 110" screen. With the zoom maxed it perfectly fits. Even the tiniest bit closer and it would come up short. In addition the mount column is adjustable. I have it at its absolute shortest which gets the projector lens just below where the ceiling drops down into the screen area.

What I would like to know is what is most likely to alleviate this issue. My two main options are:
- Lower the projector a little to potentially change the angles
- Move the projector back so that it is over the second row instead of the first row.

I don't want to lower the projector too far obviously. If I move the projector back the downsides will be that people's heads can get in the way of the image. That is a non-issue where it is even for the front row though lowering it will make it an issue. If it is behind the back row that will place the lens roughly 19'-20' from the screen. According to JVC's calculator that will lower the zoom quite a bit but not quite all the way. I would have a lot more zoom to play with than I do now. Of course that will also reduce brightness and shorten the time that I can get a good image out of low lamp mode. The only real pro for moving back is that the high lamp mode fan noise will be less problematic for both the front and back row (as it is very loud to be behind the projector in high lamp mode.)

Any thoughts?

Here is an image of the projector and seating:

https://i.imgur.com/1lkI927.jpg
Positive Gain Shimmering (Cima Neve)?


And here are some other shots that better demonstrate how the projector is mounted relative to the screen.

https://i.imgur.com/yIeg0rJ.jpg
Positive Gain Shimmering (Cima Neve)?


https://i.imgur.com/DZtfdJq.jpg
Positive Gain Shimmering (Cima Neve)?


https://i.imgur.com/iQLwn0e.jpg
Positive Gain Shimmering (Cima Neve)?
« Last Edit: August 15, 2021, 11:43:52 AM by Hyper_Eye »

AVSCraig

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Re: Positive Gain Shimmering?
« Reply #1 on: May 30, 2021, 07:31:40 AM »
I don't notice the slight shimmer on my screen, but my projector is fairly low - about 5 1/2 feet. Do you have a piece of furniture that you could do a temporary mock up of the projector lower and further back, as a test ?
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Re: Positive Gain Shimmering?
« Reply #2 on: May 30, 2021, 08:35:21 AM »
Also, how many foot lamberts are you watching at? I really don't notice this even at 20 foot lamberts. But some people are more sensitive to it than others. 
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Re: Positive Gain Shimmering?
« Reply #3 on: May 30, 2021, 03:21:20 PM »
Also, how many foot lamberts are you watching at? I really don't notice this even at 20 foot lamberts. But some people are more sensitive to it than others.
I don't have a meter to test with atm. I don't believe that is the problem though. I closed the aperture all the way down and I could still see the shimmer from the middle-front seat. Trying the projector lower isn't too big of a deal. I just need someone to get under it and hold it while I extend the column. I'm just wondering if moving the projector back and closing down the zoom might alleviate the problem. That's a little more of a pain as I will need to add an outlet in the ceiling there and move the mount. I'm not sure I have any furniture that could hold the projector high enough to test.

I don't feel any urgency to try these things because it's not too hard for me to ignore it and it's only visible when something really bright is right in the middle of the screen. Bright things tend to not be right in the center unless you are messing around with calibration patterns and I am not terribly concerned with shimmering on calibration patterns. I watched IT Chapter 2 in 4k HDR the other day and towards the end of the movie they had a lot of bright scenes and fades to white. The shimmering did present itself in those scenes.

Re: Positive Gain Shimmering?
« Reply #4 on: June 20, 2021, 02:35:27 AM »
The screen fabric speckling / shimmer is most visible in the screen't hot spot. That is why it moves as you shift seating position. It's going to be right at where the projector would be seen if your screen were a mirror. Two strategies are helpful. The first may or may not be sufficient for someone coming from from a low specularity, low gainscreen like a Carada Brililiant white. The second is likely more effective, but at a significant cost.

1. Move the projector back so the throw distance / screen width is greater than the screen gain. Doing so will expand the size of the hotspot, but also make it less distinct relative to other portions of the screen. You can experiment with this at zero cost by simply dismounting and temporarily placing the projector further back. Going to a longer throw will reduce total light output, but you get back some of it with a larger portion of the screen at a higher gain.

2. Consider switching to another fabric. Studiotek 100 definitely won't have the speckles, but you will loose image brightness and be more prone to contrast reduction from room surfaces. Studiotek 130 G4 is a similar gain to the NEVE and may have less specular issues. It's going to be somewhat up to your visual sensitivity to speckling. If you can obtain fabric swatches 1 foot square (or ideally larger), position them at your current hotspot and see if the specularity is diminished sufficiently to warrant the expense of a fabric change.



« Last Edit: June 20, 2021, 12:00:25 PM by Guy Kuo »

Re: Positive Gain Shimmering?
« Reply #5 on: June 20, 2021, 06:01:45 AM »
I went thru banding issues with my Neve where on bright pans I could see banding on the screen…Switched to ST100, no issues…

AVSCraig

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Re: Positive Gain Shimmering?
« Reply #6 on: June 20, 2021, 07:44:48 PM »
I went thru banding issues with my Neve where on bright pans I could see banding on the screen…Switched to ST100, no issues…
I've never seen banding on my Neve or ST130 unless it's in the source material. I do see banding on my father in laws Sony flat panel TV.
Direct (585) 671-2972 8:00am - 4:30pm Pacific 
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Re: Positive Gain Shimmering?
« Reply #7 on: June 20, 2021, 07:53:59 PM »
I've never seen banding on my Neve or ST130 unless it's in the source material. I do see banding on my father in laws Sony flat panel TV.
I occasionally see banding when streaming, but never with anything on disc on my Firehawk. 
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AVSCraig

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Re: Positive Gain Shimmering?
« Reply #8 on: June 20, 2021, 08:41:38 PM »
I occasionally see banding when streaming, but never with anything on disc on my Firehawk.
Source related - no doubt. 
Direct (585) 671-2972 8:00am - 4:30pm Pacific 
www.avscience.com  craig@avscience.com
We carry projectors, screens, speakers, receivers etc. !!
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Re: Positive Gain Shimmering?
« Reply #9 on: June 20, 2021, 09:18:46 PM »
Source related - no doubt.
Absolutely it's source related. Streaming has come a long way (video wise), but disc still provides a superior experience. 
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Sound & Vision Magazine

Re: Positive Gain Shimmering?
« Reply #10 on: August 15, 2021, 12:03:56 AM »
I went thru banding issues with my Neve where on bright pans I could see banding on the screen…Switched to ST100, no issues…
I assume that means you bought a new frame as the ST100 material is not available for use with the Cima frame?

Re: Positive Gain Shimmering?
« Reply #11 on: August 15, 2021, 09:41:41 AM »
I assume that means you bought a new frame as the ST100 material is not available for use with the Cima frame?
You are correct, the ST100 material is not generally offered for use with the Cima frame

Re: Positive Gain Shimmering?
« Reply #12 on: August 15, 2021, 11:39:57 AM »
You are correct, the ST100 material is not generally offered for use with the Cima frame
One of the original selling points of the Cima FF to me was that the frame width was just right for the space I was installing it in. Even 1/2" increase would be problematic. It looks like the WallScreen 2.5 series would be a perfect replacement. I'm definitely considering it. I just need to determine the best way of selling my barely used Cima FF Neve. I did try projecting from farther back and it did not resolve the problem adequately. I don't really need the 1.1 gain. Neutral gain would be just fine in my theater. I am able to kind of ignore the shimmering but I can't say I'm completely satisfied. I'd rather get rid of it.

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