120" Tri-Color Screen Testing: "Flexi" colors from Carl's Place - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 24 Old 07-31-2019, 06:19 PM - Thread Starter
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120" Tri-Color Screen Testing: "Flexi" colors from Carl's Place

Hey guys, I reached out to Carl from Carl's Place to do some testing on the three different "flexi" materials he offers for DIY screens. He was cool with the idea and sent me a pretty sweet 120" screen with the Flexiwhite, Flexigray, and Ambient Light Rejecting (ALR) flexi materials welded together to make up each 1/3 of the screen.


I'm wanting to get some good pictures/patterns for comparing the colors and thought I would see if there were any you all could suggest. I already have a few in mind and will also be doing stills from some movies as well. Going to try to get some video footage of how it looks in action, but not sure how the colors will look through my camera.



The setup being used will be:

  • 120" ALR/Gray/White screen
  • PS4 or computer for movie stills or images
  • Panasonic AE-8000U projector (all settings will be zero'd and picture set to normal)
Room is fairly light controlled during the day (blackout curtains do a great job). Wall and ceiling is Software Gray from SW. I will be testing how the image looks in different lighting conditions and angles. I'll have daylight directly behind seating area during the day when the blackout shades are open and have dimmer lights throughout the basement. Complete darkness images will be taken at night to be sure no light is leaking in. Pictures/video will be taken with a Panasonic G80 with stock lens.



I'm no expert in this area, but wanted to get some good images on a large scale to help both myself and others decide on which color is right for their situation. So.... any test images you'd like seen?


Thanks!






Edit: Here is the complete video. Thanks for you helps guys!


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post #2 of 24 Old 08-02-2019, 11:30 AM
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Interesting experiment. Just understand that the projector, screen and room environment work together as a system. Ideally the projector settings are used to optimize the projector image to the screen and room environment. In your case when comparing the same projector image in the same room environment simultaneously on three different screen materials your projector can only be calibrated to produce the optimum image on one section at a time. It will not be properly calibrated for the other two materials and so comparison results will be skewed. For example, the formal way to compare a gray screen and a white screen is to increase projector lumens for the gray screen so that it measures equally bright as the white one.

Similarly different camera settings can skew any camera image comparisons of the same image on the three screen surfaces. Ideally screen comparisons are performed with the projector individually calibrated to the optimum settings for each different screen and the results measured with calibrated test equipment. This is beyond the scope of most amateur reviewers so while informal impressions can be helpful to some extent they can also be somewhat misleading.
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post #3 of 24 Old 08-02-2019, 12:39 PM - Thread Starter
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Originally Posted by Dave in Green View Post
Interesting experiment.....
Completely agree with everything you said. I know it's a whole package sort of deal. I touch on that in the video and let people know they need to look at their setup to calculate ft lamberts as well. And I also go over how I'm no expert, and the picture quality is limited to my ability and equipment. After doing some images/video, I really think the video will show how outside light effects the screen contrast and black levels. I spent a lot of time adjusting camera settings to best capture what I was seeing in person. There will obviously be ways to improve things after calibrating to a certain screen color, but it gives a good idea at least. I just hadn't seen a larger scale side by side test like this, so I thought I would give it a try.
I'm sure there are many professional or better educated people out there that will have many criticisms of how things were done and/or look. But hey, it's more material out there to look at and it opens a discussion if people have questions.



I've pretty much got all of the test material I wanted to try. Should have a video put together by Sunday.
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post #4 of 24 Old 08-02-2019, 05:41 PM
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@blister , I feel you know exactly what you want to do and how you want to go about it.



There is nothing wrong at all with setting up the PJ for the white screen and then making comparisons with the darker screens to see how "THEY" perform, Yeah...it's a given that any particular Screen that receives an image that has been optimized via Calibration will look it's best....but just the same there are screens whose performance envelop is more expansive and able to be adaptive to both PJ attributes and room conditions.


The exact same thing applies to the use of a Camera (still or video). You can run an experiment into the ground and make it so convoluted that any results can be viewed only in a singular, not a group fashion. Absolutely one can cause a Camera to push an image into inaccuracy...just to make an image look better.....but on here it's always a matter of trust. Make adjustment in composition and / or function...but only so much that what you present represents what your actually seeing.



Basically, over the years many have tried to dissuade or even discourage / disparage such efforts....perhaps unintentionally at times, at others with quite obvious intent.

@blister .....do what you want in the manner you feel will best represent the visual results you see in person. If the content you post meets with YOUR approval and to YOU looks close enough to be considered an accurate representation, ignore those who might say the results are skewered in favor of one point or another. Your not expected to make absolute individualized determinations beyond what you can see up on your triad composition screen.


And BTW....over the years there have been a great many full size and largish composite presentations....but all those involved other similar products and different projectors....as well a various and varied room conditions. They exist....they are just not up on the forefront after 3-4-6-10 years gone.


I look forward to your posted evaluation. Having dealt with just about every Carl's offering over the last 12+ years, and having worked with perhaps over 15+ PT-AE 8000u installations, I pretty much already know what to expect. It will be great to compare opinions and experiences.

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post #5 of 24 Old 08-03-2019, 08:08 PM - Thread Starter
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@MississippiMan thanks for the input man. I figured you would chime in, I've read and learned many things from your posts over the past 2 years along this journey...

I haven't really had any negative feedback on the idea so far, most have been really excited about it. I honestly thing with calibration any if these screens would look fantastic, it's just what sort if ambient light level are you looking at or compromises you are willing to deal with.

Since you joined the discussion and have had extensive experience with everything I am looking at, I have a few questions regarding my setup...
Quick initial impressions:
Flexiwhite- great color, seems the most accurate representation. Blacks are ok, but left me wanting darker scenes to seem, well, darker... Any amount of light degrades image quickly
Flexigray- colors muted slightly, most whites are dulled down, never seems like a true bright white. Blacks are pretty nice. Very noticeably darker. Almost no degradation of picture with the small amount if light we usually use. Just doesn't have the pop of bright color seen in the others.
ALR- I have mixed feelings on this one. Contrast is amazing. Deep rich blacks. Didn't really notice how much the color actually pops until watching a full movie last night. Brighter whites than the gray, almost matches the white screen. Holds image quality pretty darn well even with more than normal ambient lighting we would use. Might lose some of the detail in the black just because it is so dark. I actually really like this one just cause the contrast is stunning, but also makes me a little nervous as the viewing angle does slightly alter brightness levels depending on where you sit.

I went into this thinking the flexigray would be my favorite, but that ALR has me second guessing that. The white just won't do well in my setting I don't think, and even with a completely dark room, I'm just a little disappointed in the black performance.
With your experience with the materials and AE8000u, AFTER calibration, did you have a material you felt stood out in this combination? I plan to get it professionally calibrated once I make my final screen. Any input you have is appreciated!

Going to watch more tonight and hopefully get the video up by tomorrow evening if I have time.

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post #6 of 24 Old 08-04-2019, 07:16 AM
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Quote:
Originally Posted by blister64 View Post
@MississippiMan thanks for the input man. I figured you would chime in, I've read and learned many things from your posts over the past 2 years along this journey...

I haven't really had any negative feedback on the idea so far, most have been really excited about it. I honestly think with calibration any if these screens would look fantastic, it's just what sort if ambient light level are you looking at or compromises you are willing to deal with.

Since you joined the discussion and have had extensive experience with everything I am looking at, I have a few questions regarding my setup...
Quick initial impressions:
Flexiwhite- great color, seems the most accurate representation. Blacks are ok, but left me wanting darker scenes to seem, well, darker... Any amount of light degrades image quickly
The Flexi-White is indeed the most Color correct....and in a non-ambient light situation, while it does an admirable job, it's Black Lever rendition and any Contrast preservation is wholly dependent upon two extremely important factors.
  • The actual Black / Contrast performance the PJ itself is capable of.....
  • How much impact room reflections from the projected content make on the image.
Any / All Unity Gain up to 1.3 gain White screens suffer from black level drop (washout) and reduced contrast under ambient light....never mind actual direct light intrusion. That is why those who have dedicated Theaters that have none of such remain convinced that going with a White screen is preferred above all else.

Quote:
Flexigray- colors muted slightly, most whites are dulled down, never seems like a true bright white. Blacks are pretty nice. Very noticeably darker. Almost no degradation of picture with the small amount if light we usually use. Just doesn't have the pop of bright color seen in the others.
Yep yep.....the Flexi-Grey does mute the dynamics of any larger sized image that comes from a PJ with lower Lumen output. It achieves it's deeper Blacks via suppression (attenuation) of "ALL" incoming light. While that does deepen the Black Floor, it does and always will dull down the brilliance of bright colors and make White dingy UNLESS that overall tendency toward attenuation is mitigated by additional Lumen punch and effective calibration via a decrease in light output and Gamma adjustments across the gamut of the Color spectrum. The fact that is does not severely attenuate is a point in it's favor, but I personally don't advocate it's use much unless it's pared with a PJ over over 3K lumen

Quote:
ALR- I have mixed feelings on this one. Contrast is amazing. Deep rich blacks. Didn't really notice how much the color actually pops until watching a full movie last night. Brighter whites than the gray, almost matches the white screen. Holds image quality pretty darn well even with more than normal ambient lighting we would use. Might lose some of the detail in the black just because it is so dark. I actually really like this one just cause the contrast is stunning, but also makes me a little nervous as the viewing angle does slightly alter brightness levels depending on where you sit.
You pretty much nailed that evaluation. It's biggest fault is indeed it's tendency to crush Black oriented shadow detail, but that is kinda a result of it's focus on maintaining gain off a darker surface in the manner it does. Most all ALR Screens are Angular or Retro-Reflective....opting to deliver light back to a more restricted viewing position, and it is exactly the gain that also erases some shadow details within darker content. It's unfortunate that in the process of increasing the appearance increased Color saturation that the added gain suppresses subtle detail, but that is a well known caveat that drives so many White Screen advocates to dismiss the use of such Screens unless the need for them in less that optimal viewing conditions makes them mandatory.

Quote:
I went into this thinking the flexigray would be my favorite, but that ALR has me second guessing that. The white just won't do well in my setting I don't think, and even with a completely dark room, I'm just a little disappointed in the black performance.
That experience and opinion would change at least a bit with a PJ in use like a Epson 5040-50 and all the more so with a vintage JVC (x790 / RS 540 > and up) The Panny's stated Contrast is ....well overstated, and it's smooth screen Tech is also a contributing factor. That didn't keep me from using it extensively though, because I had the advantage of projecting onto ideally suited painted surfaces, most all of which were taking advantage of the Panny's Lens memory feature. But in the all in all, a White will always be only as good a performer as the PJ in combination with a Room's circumstance can make it be.

Quote:
With your experience with the materials and AE8000u, after calibration, did you have a material you felt stood out in this combination? I plan to get it professionally calibrated once I make my final screen. Any input you have is appreciated!
Well...........I never did like the ALR offering, as in most all cases viewing cone issues were at the forefront, and the sacrifice of detail was always unacceptable.

The Flexi-Grey was a good standby when painting was not an option and the PJ had acceptable Calibration abilities. The Panny falls into the latter description, but you can expect to lose some brightness as the result of both the Grey surface and the resulting needed calibration. Only the tweaking of the Gamma curves on both Colors and Whites can help, and I'm certain that as long as the Screen size remains at 120"diagonal or less you'll be happy with the end results using the existing PJ.

The ONLY time I've used (...or use...) the Flex-White was when it is being used as a excellent Canvass on which I would paint a High Contrast, Positive Gain ALR solution...because just as your stated preference, I want screens that come as close to doing it all under most any normal circumstances and situations. The tendency for some to dismiss the need of such a surface in a dark, reflection controlled room in preference to a White isn't going to change if the PJs has exceptionally good contrast built in. But all the same, when the saturated colors and shadow detail are both present in a dark room situation...the result is an almost 3-D like realism. Once you experience that....nothing else will ever look as good again.

However no Unity or positive Gain White is ever going to "improve" color saturation (...just maintain it at best...). The Blacks will only be as good as all the other aspects of the viewing situation will allow.

Of the Three......................I'd cast my vote for the Flexi-Grey, because you can recoup enough White performance to see a difference, all the while achieving just enough ALR(resistance) performance to make a difference over Flexi-White . AND.....considering the very real fact that someday you will upgrade that 'ol Panny, and any newer PJ of at least it's original ilk is chosen, the Flexi-Grey won't disappoint.

Now of course.....one huge advantage you now have and should avail yourself of is trying to bone up on how to at least basically do some simple calibration, because you have before you all three screen examples. Calibrate to the Flexi-Grey first, allow it's image to compare to the others, and if it satisfies.....run with it.

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post #7 of 24 Old 08-04-2019, 05:11 PM - Thread Starter
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Really appreciate all the feedback @miss isspssiMan ! Also good to know I was on the right track with interpreting image quality... I'll definitely play around with calibrating to the gray to see how good I can make it look, but that won't be a part of this particular video. I'm pretty excited to get a screen going, the image quality and brightness is amazing compared to my darker gray wall lol
Edit: And I will be looking to upgrade projectors here in the next 1-2 years. I'll have a healthy budget when that time comes, probably up to $5-6k, so I'm sure I'll have a much brighter PJ to work with then as well. I think the gray will work well in my setting.

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post #8 of 24 Old 08-05-2019, 09:37 AM
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Originally Posted by blister64 View Post
… Quick initial impressions:
Flexiwhite- great color, seems the most accurate representation. Blacks are ok, but left me wanting darker scenes to seem, well, darker... Any amount of light degrades image quickly
Flexigray- colors muted slightly, most whites are dulled down, never seems like a true bright white. Blacks are pretty nice. Very noticeably darker. Almost no degradation of picture with the small amount if light we usually use. Just doesn't have the pop of bright color seen in the others. ...
These observations are in line with the difference between neutral density 1.0 gain matte (Lambertian) white and neutral density <1.0 gain matte (Lambertian) grey screens that has been discussed at length on this forum over the years as @bud16415 can confirm. What you saw is a perfectly logical result of what happens when you project the same image on both screens with a projector on the same settings.

The rest of the story is that in order for the whites and colors to look the same on the grey screen as the white one the projector must be adjusted to produce the same screen fL on the grey screen as the white one. For example, with the same projector settings a 0.8 gain matte grey screen will measure 80% of the fL of a 1.0 gain matte white screen.

If you were using two identical projectors to project on those two screens and the lumens produced by the projector for the 0.8 gain matte grey screen were increased to compensate for the 20% loss in fL from the 1.0 gain matte white screen the whites and colors would be equally bright on both screens. On the same projector settings the grey screen simply trades away brighter whites and colors in return for darker blacks.

With appropriately different projector settings for each screen the advantage of the matte grey screen over the matte white screen is in reducing the image washout effect of room cross-reflections -- screen image light reflected onto light-colored room surfaces where the light is reflected back onto the screen. The 1.0 gain matte white screen will reflect 100% of room cross-reflections while the 0.8 gain matte grey screen will reflect only 80% of room cross-reflections. This can at least slightly reduce image washout. But if the projector isn't adjusted to throw more lumens onto the grey screen to match the brightness of the white screen it becomes an apples-oranges comparison.
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post #9 of 24 Old 08-05-2019, 01:21 PM - Thread Starter
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@Dave_In_Green Yep, that's pretty much what I was seeing and thinking. I tried to explain that a bit in the video as well. I really appreciate your input! I've learned quite a bit through this process and looking forward to tweaking the projector settings to see what sort of image I can get on the Flexigray material.



Video is done, I'll leave a link in the original post above. It was pretty hard to capture exactly what I was seeing (you'll see the difference in using overhead lights vs outside light source) but I feel I accomplished what I set out to do. Hopefully it is helpful to see these images on a large scale. Thanks guys!

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post #10 of 24 Old 08-05-2019, 01:50 PM
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Originally Posted by Dave in Green View Post
These observations are in line with the difference between neutral density 1.0 gain matte (Lambertian) white and neutral density <1.0 gain matte (Lambertian) grey screens that has been discussed at length on this forum over the years as @bud16415 can confirm. What you saw is a perfectly logical result of what happens when you project the same image on both screens with a projector on the same settings.

The rest of the story is that in order for the whites and colors to look the same on the grey screen as the white one the projector must be adjusted to produce the same screen fL on the grey screen as the white one. For example, with the same projector settings a 0.8 gain matte grey screen will measure 80% of the fL of a 1.0 gain matte white screen.

If you were using two identical projectors to project on those two screens and the lumens produced by the projector for the 0.8 gain matte grey screen were increased to compensate for the 20% loss in fL from the 1.0 gain matte white screen the whites and colors would be equally bright on both screens. On the same projector settings the grey screen simply trades away brighter whites and colors in return for darker blacks.

With appropriately different projector settings for each screen the advantage of the matte grey screen over the matte white screen is in reducing the image washout effect of room cross-reflections -- screen image light reflected onto light-colored room surfaces where the light is reflected back onto the screen. The 1.0 gain matte white screen will reflect 100% of room cross-reflections while the 0.8 gain matte grey screen will reflect only 80% of room cross-reflections. This can at least slightly reduce image washout. But if the projector isn't adjusted to throw more lumens onto the grey screen to match the brightness of the white screen it becomes an apples-oranges comparison.
I read this thread the other day and wanted to reply but didn’t because of being down that same road so many times and knowing the non scientific rationale that is always expounded by a few individuals.

I do think it is great Carl was willing to make a great test screen like that for a member to investigate, but on the other hand the fact that they made it makes me wonder if Carl is really into the science behind screens himself. Although all the companies send out samples and give no explanation as to what to do with them.

You did a great job explaining things for the OP.

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@blister64 , the most important thing in any of our efforts to help others by sharing data is to try to follow a version of the physicians' Hippocratic Oath: First, do no harm. In this case doing no harm is trying not to confuse or mislead others with incomplete data. It can take a lot of effort to describe in fine detail all the little nuances, so we all try to work together to fill in the blanks in a collaborative effort. Some of the neutral matte grey screen data that @bud16415 and I have often discussed on the forum comes directly from @Don Stewart , chief technology officer at Stewart Filmscreen, who has been generous in sharing his company's experience with this type of screen material on this forum.
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@blister64 , the most important thing in any of our efforts to help others by sharing data is to try to follow a version of the physicians' Hippocratic Oath: First, do no harm. In this case doing no harm is trying not to confuse or mislead others with incomplete data. It can take a lot of effort to describe in fine detail all the little nuances, so we all try to work together to fill in the blanks in a collaborative effort. Some of the neutral matte grey screen data that @bud16415 and I have often discussed on the forum comes directly from @Don Stewart , chief technology officer at Stewart Filmscreen, who has been generous in sharing his company's experience with this type of screen material on this forum.
I'll definitely look up some of his/your posts on the matter. And not too sure which side of the line you are thinking I'm on with the do no harm, but like I said, it was educational for me and I tried to pass along what I learned in the video. I am no where near an "expert" in any of my videos, I just try to share my experiences to hopefully help others if they have an interest. I point out in the video that this is not a complete or conclusive testing of any materials and that it should only be used as a tool to better understand the effects of light on the materials and used in conjunction with other research that should be done.

I appreciate all the discussion and will look up more of what you guys have posted about the materials. There's a lot to learn...

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post #13 of 24 Old 08-06-2019, 06:38 AM
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I'll definitely look up some of his/your posts on the matter. And not too sure which side of the line you are thinking I'm on with the do no harm, but like I said, it was educational for me and I tried to pass along what I learned in the video. I am no where near an "expert" in any of my videos, I just try to share my experiences to hopefully help others if they have an interest. I point out in the video that this is not a complete or conclusive testing of any materials and that it should only be used as a tool to better understand the effects of light on the materials and used in conjunction with other research that should be done.

I appreciate all the discussion and will look up more of what you guys have posted about the materials. There's a lot to learn...
You clearly are trying to do no harm. I was just trying to explain in general why others will jump into the conversation to help fill an any blanks they might see. That's what I meant by saying these discussions tend to become collaborative. Everyone should appreciate your efforts and all comments from others should be constructive. If anyone gets overly critical of your efforts others will surely come to your defense.

I'll quote a good post for you to read from Don Stewart (directed to Bud) from a few years ago describing how Stewart Filmscreen in 1979 developed the first commercial use of low gain, neutral density, Lambertian grey front projection screens for Disney. In fact the whole thread is worth reading so I'll also include a link to the thread:

avsforum.com/forum/23-screens/2376026-white-screens-vs-gray-screens-color-pop-whites.html

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Originally Posted by Don Stewart View Post
Bud, you may appreciate this story because you are a proponent of low gain Lambertion gray screens. We at Stewart have had the honer to design, engineer and manufacture all of the Disney 360 Circle Vision theater screens and framing systems which are located at the Disney theme parks throughout the World. (See photo below) When we built the first system, we assembled it on a sound stage at the Disney Studios in Burbank. This nine segmented screen system was to be used for post production and sound editing only. Anyway, the screens that Disney specified and ordered for the mock up theater were Snomatte 100 lamberlion white diffusion screens. Well... you can guess what happened when they fired up the nine projectors for the first time. The theater looked like the inside of your refrigerator when you open its door. The 360 degree screen vista washed out the adjacent screens and cross reflected to the opposing screens on the other side of the theater. It was a mess and the studio brass were not to happy as a lot of money had already been spent on shooting the raw film footage. After some head scratching by both the Disney and Stewart teams the idea came up to engineer and produce a front projection ND gray screen. What initiated the ideal was Stewart and other screen manufactures had been producing dark gray contrast enhancing ND rear projection screens for decades. Why not do the same for front projection? So after a few weeks of intense R&D Disney approved a very dark gray, 0.4 gain FP screen surface. Since the 0.4 gain screens were not as efficient as the 1.0 Snowmatte 100 screens, Disney had to increase the lamp output by 250%. But they did not care as the project's success was riding on the gray screens. In fact, Disney engineers have a saying called the bigger hammer theory. " If the hammer in hand does work, then break out a bigger hammer" or something like that. In this case they broke out the sledge hammer. Also, the nine gray screens had to be lambertion with no gain coatings because with 200 or so viewers in the theater, each of the nine screens had to distribute the exact same luminance to each viewer no matter where they were positioned in the theater. To the best of my knowledge, these were the vary first commercial gray screens. It was around 1979 and I was a very young man at the time.
OP, sorry if I derailed your thread but thought this was worth sharing. Carry on.
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post #14 of 24 Old 08-11-2019, 02:21 PM
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If you were using two identical projectors to project on those two screens and the lumens produced by the projector for the 0.8 gain matte grey screen were increased to compensate for the 20% loss in fL from the 1.0 gain matte white screen the whites and colors would be equally bright on both screens. On the same projector settings the grey screen simply trades away brighter whites and colors in return for darker blacks.
What happens to the black floor of the grey screen when the projector outputs 20% more light (than with the white screen)? Will both screens look the same, with the only difference being the grey screen will reflect 80% of the ambient light?

At one point I had an Elite CInegrey (matte) 1.0 gain to compare with the Cinegrey 3D (1.2). PJ Benq W2000(HT3050) on SmartEco, 700h lamp, x1.5 throw range, 106" screen. White walls.
The colors on the matte screen were very washed out, definitely not the way as they're presented in the video above, which is very similar to the ALR portion of the screen. Watched a few things, The Dark Knight was ok, but nature documentaries had the colors striped. The blacks were deeper on the matte screen.
I've seen pictures of grey screens looking fine, even with projectors that are not bright, such as @bud16415 's setup, which has a similar projector.
Was it because of the lack of lumens, was the projector too far away?
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post #15 of 24 Old 08-11-2019, 05:09 PM
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@noob00224 , think of a <1.0 gain neutral density matte grey screen as just a darker neutral density matte white screen. Reducing gain has the same effect as reducing projector lumens. Nothing else about the image should change. This of course is in a hypothetical all black room where no screen image light is reflected from the room surfaces back onto the screen as I described the effect of cross reflections in one of my previous posts. Each individual case such as the ones you and @bud16415 experienced would need to have all the fine details considered in order to do any analysis of why you saw what you saw as there can be variables beyond the gain difference of neutral density matte grey and white screens in different environments that would keep it from being a direct apples to apples comparison.

EDIT: Forgot to mention that the two screens you compared both had directional gain. By definition a matte screen is Lambertian and reflects light equally in all directions that can't exceed 1.0 gain. A grey screen can't be matte if it has 1.0 gain or higher because it's darker than a matte white screen. With matte (Lambertian) screens only a white one can have 1.0 gain and any screen with >1.0 gain has to have directional gain to achieve greater brightness at the viewing position than the image light the projector is throwing on the screen. By directing >1.0 gain at one viewing position a directional screen is going to deliver <1.0 gain at other viewing positions. So lots of variables in your comparison beyond the straightforward comparison of matte white and matte grey screens.
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post #16 of 24 Old 08-12-2019, 07:05 AM
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With matte (Lambertian) screens only a white one can have 1.0 gain and any screen with >1.0 gain has to have directional gain to achieve greater brightness at the viewing position than the image light the projector is throwing on the screen. By directing >1.0 gain at one viewing position a directional screen is going to deliver <1.0 gain at other viewing positions. So lots of variables in your comparison beyond the straightforward comparison of matte white and matte grey screens.
The above is not a universally applied stipulation. There are exceptions that vary from what many seem to consider a steadfast and immutable rule.

Introducing an application where reflective elements are suspended within a translucent medium be it Grey or White...and arrayed at various angles, can help to both retain or even slightly increase gain while also diffusing and distributing light within said translucent medium....resulting in light being distributed in a more diverse and disperse orientation.

Such will result in a higher than Lambertian Gain on Axis, but not as severe a case of off-Axis Gain loss with Retro or Angular surfaces. This is seen in a few Mfg & DIY screen apps with +>Gain whose 1/2 Gain points are either close to 80 degrees or nonexistent (...never reach down as low as 1/2 Gain...). That is not to say there is no loss, just not nearly as severe.

Obviously, of the three examples, the ALR Screen is the only one that exhibits any degree of Angular Reflective properties, so it alone represents a deviance from the reflective properties of the other examples. Yet the OP did a sufficient job addressing and describing those differences.

In any case, over complicating the descriptive results of what is a plainly simple visual comparison study, one meant to derive the visual difference inherent between 3 distinctly different surfaces receiving the exact same content while "side-to-side" ignores the OP's original intent. Any specific calibration or adjustments made to favor either of the non-White surfaces would have created skewered results that were not included in the original intent. His intent was to see how each screen reacted to the same projected content, with each "side-to-side" example subjected to the same exact conditions. Any other more complicated attempt would require a set-up the OP was neither provided nor himself expected to present.

As such, wandering away from the stated observations of the OP tends to distract others from really understanding the OP's end results and observations, and almost discounts his posted results as being both inconclusive and erroneous.

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post #17 of 24 Old 08-12-2019, 08:42 AM
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Focusing on the science, a true Lambertian (matte) screen adheres to a universally accepted scientific principle known as Lambert's cosine law (aka Lambert's emission law or cosine emission law) that dates back to 1760. Wikipedia has a simple explanation of how it works for any surface (including projection screens):

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A surface which obeys Lambert's law is said to be Lambertian, and exhibits Lambertian reflectance. Such a surface has the same radiance when viewed from any angle. This means, for example, that to the human eye it has the same apparent brightness (or luminance).
Any surface or screen that doesn't obey Lambert's law would therefore by definition be non-Lambertian. A non-Lambertian surface by definition must have directional reflectance, i.e. a different radiance when viewed from different angles. To the human eye directional reflectance has different apparent brightness (or luminance) when viewed from different angles.

Marketing claims for any screen material producing >1.0 gain when viewed from any angle so that to the human eye it has the same apparent brightness (or luminance) would be in contradiction of Lambert's law and not supported by credible independent scientific sources.
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post #18 of 24 Old 08-12-2019, 09:43 AM
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.......and yet the differences have been observed and documented by many who are wholly independent of the Mfg genre.


You also allaying that all such stated claims fall within the narrow confines of your stated depiction. They do not...and not being such absolves them of being held to such a restrictive overview.



Blindly accepting any such narrow description is myopic or worse, willingly blind to any potential advances. A Trieste authored in 1760 cannot be effectively applied to methods and materials that were not in existence at the time. It represents an accepted benchmark...a proven scientific guideline, but does not and cannot exclude possible advances / changes not addressed 259 years ago. And no currently published White Paper that does not address every possible alternative can be construed as being absolutely definitive.


As I stated...it seems that the basis for argument is simply that any Screen not adhering to the exact attributes attributed to a Lambertian surface isn't "Lambertian". Can anything be more obvious? Or unnecessarily stated? Stating such obvious points never seems to stop individuals using such narrow overviews to bolster what amounts to being moot points. And not surprisingly....no one else on this Thread stated otherwise, only that there are ways and methods to help counteract (not eliminate) the deficiencies inherent in positive gain surfaces....so why is it hard to comprehend or accept that a surface with a on axis 1.3 gain that has the ability to also direct light to the side cannot follow a similar curve downward toward <1.0 gain yet not reach down so far as to bottom out at 1/2 Gain at 80 degrees or less off center? It should not be dismissed outright as being impossible.....it is indeed possible...but almost always there are a few who instead choose to ignore such things and instead dance around those possibilities while waxing effusive on "old school" and even ancient dictates that are supposedly ironclad.



Let those items be brought even remotely into question and what follows are claims that the person so noted as relating such is ignoring "science" because their statements vary from accepted norms. Much the same occurred regularly when mention was made that on-screen contrast was improved with certain applications, alluding that what was actually being said was that the PJ's own contrast was being improved. Silly and misleading arguments made simply for the sake of being argumentative.



But ya know all that isn't even OT for the example illustrated on this Thread. No....such confining comments that really are not applicable are instead made as "talking points" that distract from the real purpose intended. To show the difference between three disparate surfaces receiving identical content under identical conditions.


Of course the OP might take all that and decide to produce a Yeoman's effort to include each and every working point and variable for each separate screen. But somehow I think that such an effort itself would be picked apart down to the bones by those with little or no real interest except for being dismissive and argumentative.

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post #19 of 24 Old 08-13-2019, 01:20 PM
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The above is not a universally applied stipulation. There are exceptions that vary from what many seem to consider a steadfast and immutable rule.
This is why they need to take that darn S out AVS forum. Without science all things are possible. Science has always been holding back progress. We have all these problems in the world because we keep telling the guys building perpetual motion engines it can’t be done.

Don’t get me started on engines that run on water or making gold from lead because those things can be done if we get rid of science.

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post #20 of 24 Old 08-13-2019, 01:28 PM
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Those who refuse to or cannot envision that accepted Science cannot be rethought. and that the Future holds surprises undreamed of are condemned to live a very dull and mundane existence.

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post #21 of 24 Old 08-13-2019, 02:07 PM
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Light is energy and if you can increase the light on axis and not decrease light off axis then you have created energy out of nothing. That would be the greatest invention of all time and could be scaled up to solve every problem man faces ahead.

No one has said people don’t need to be inventive or creative and there is much left to be discovered and even more useful combinations of existing science, but people need to know there are fundamental principals of science that are cast in stone in the real world. No amount of colorful language will explain away simple science.
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post #22 of 24 Old 08-14-2019, 08:31 AM
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For all our speculation about the future, no one really knows all the changes it might bring. Focusing on today's reality, anyone who contends that the universally accepted scientific principle known as Lambert's law has been disproven would need to present scientific data to back up the claim in order to be considered credible.

Hint: "They say" is not considered scientific data.
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post #23 of 24 Old 08-14-2019, 09:34 PM
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Originally Posted by blister64 View Post
Hey guys, I reached out to Carl from Carl's Place to do some testing on the three different "flexi" materials he offers for DIY screens. He was cool with the idea and sent me a pretty sweet 120" screen with the Flexiwhite, Flexigray, and Ambient Light Rejecting (ALR) flexi materials welded together to make up each 1/3 of the screen.


I'm wanting to get some good pictures/patterns for comparing the colors and thought I would see if there were any you all could suggest. I already have a few in mind and will also be doing stills from some movies as well. Going to try to get some video footage of how it looks in action, but not sure how the colors will look through my camera.



The setup being used will be:

  • 120" ALR/Gray/White screen
  • PS4 or computer for movie stills or images
  • Panasonic AE-8000U projector (all settings will be zero'd and picture set to normal)
Room is fairly light controlled during the day (blackout curtains do a great job). Wall and ceiling is Software Gray from SW. I will be testing how the image looks in different lighting conditions and angles. I'll have daylight directly behind seating area during the day when the blackout shades are open and have dimmer lights throughout the basement. Complete darkness images will be taken at night to be sure no light is leaking in. Pictures/video will be taken with a Panasonic G80 with stock lens.



I'm no expert in this area, but wanted to get some good images on a large scale to help both myself and others decide on which color is right for their situation. So.... any test images you'd like seen?


Thanks!
thanks for sharing. I found this quite interesting. It's always really tough comparing a white and grey screen at the same time(since they really need two different settings on the projector), but I found myself focusing on the difference between the grey and ALR sections. It was fascinating how in some situations the grey looked better, and in others the ALR looked better. I haven't really seen a side by side demo that clearly showed under what conditions each was superior, so that was pretty cool.
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post #24 of 24 Old 08-16-2019, 08:45 AM - Thread Starter
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Originally Posted by fierce_gt View Post
thanks for sharing. I found this quite interesting. It's always really tough comparing a white and grey screen at the same time(since they really need two different settings on the projector), but I found myself focusing on the difference between the grey and ALR sections. It was fascinating how in some situations the grey looked better, and in others the ALR looked better. I haven't really seen a side by side demo that clearly showed under what conditions each was superior, so that was pretty cool.
Yea it was very interesting to see in person. Glad it was helpful for you! I agree, depending on the image and light source, one looked better than the other. I will say though, I just got the flexigray screen made up and did an initial calibration on it. Watched about an hour worth of material and it looks fantastic! Obviously all of the screens could have benefited from calibration for each. Very happy with the results though. I'll have another video on it on my channel soon.
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