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assessing screen surface samples and black / white level


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Hi all, 

 

I have some vividstorm ALR screen samples coming and had a generic question I thought was best asked here. 

 

When you are comparing the performance of a screen sample against your current screen surface it seems perfectly valid to simply attach the sample to the current projection surface and compare it with some dark and bright content. 

 

However I've seen people do this on the avsforum and then complain about how such and such a sample is too dark with their projector or contrast isn't as good vs their current surface so they won't be buying etc. 

 

To me at least, the step that people seem to miss is, if you were looking to buy a full screen version of that sample, wouldn't it be a good idea to position the sample right over bars 16 and 17 of a black level test pattern and set the brightness and then bars 235 and 236 of a while level test pattern and set the contrast? 

 

To those that have dabbled in calibration out there Is that thinking valid? Or is this not a valid test to assess how that sample might perform on its own as a full screen surface with respect to its overall brightness and contrast? 

 

I note that I've done a fair bit of self educating online and at home with a version a i1 display pro, avs709 test patterns, hcfr, I've got a current version of Chromapure (for which I've read most of the manual) and read a lot of posts on the avsforum/curt palme forum on calibration. I haven't got very good delta e results trying to calibrate a white screen in a living room environment though (understandable) 

 

So essentially I've got some basic knowledge that I've built up, probably not a complete idiot on the subject. Just enough to be semi dangerous :)

 

Would appreciate any thoughts. 

 

Cheers

 

Steve

 

 

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What are you trying to achieve with screen fabric samples? I can't see the point of it. The reputable screen manufacturers know which of their products best suit particular projectors in various environments. You don't need to mess with fabric samples. Just rely on the advice of the screen manufacturer.

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16 minutes ago, brodricj said:

What are you trying to achieve with screen fabric samples? I can't see the point of it. The reputable screen manufacturers know which of their products best suit particular projectors in various environments. You don't need to mess with fabric samples. Just rely on the advice of the screen manufacturer.

Well validate manufacturers cliams to an extent, some of which are vague - recommended throw for example. My projector fits within the specs they (vividstorm) suggested were required in terms of lumens for their ALR materials, but I guess I want to test that at my desired throw. If this were a straight out white screen in a dark coloured light controlled room, then I wouldn't bother, i'd just order it. but it isn't. I may well colour treat the room in the not too distant future, but the windows will continue to be there. Hence at least taking a look at the potential of ALR. 

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7 hours ago, usethe4c said:

To me at least, the step that people seem to miss is, if you were looking to buy a full screen version of that sample, wouldn't it be a good idea to position the sample right over bars 16 and 17 of a black level test pattern and set the brightness and then bars 235 and 236 of a while level test pattern and set the contrast? 

That sounds logical as far as it goes.

 

(Room ANSI test pattern black level deteriorates with increased screen reflectivity. I would note that a small sample that is more reflective than the existing screen will increase the overall level of reflected light in the viewing room (e.g. for the  ceiling and walls, and viewers' clothing) by only a very small percentage. It may well give more visible contrast for the new sample when being tested, but replacing the whole of the screen might not give as good a result, because of a deterioration in the room ANSI black level.)

Edited by MLXXX
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25 minutes ago, MLXXX said:

That sounds logical as far as it goes.

 

(Room ANSI test pattern black level deteriorates with increased screen reflectivity. I would note that a small sample that is more reflective than the existing screen will increase the overall level of reflected light in the viewing room (e.g. for the  ceiling and walls, and viewers' clothing) by only a very small percentage. It may well give more visible contrast for the new sample when being tested, but replacing the whole of the screen might not give as good a result, because of a deterioration in the room ANSI black level.)

Yes, that makes sense. Thanks for the comment. My existing main screen is just a basic 90“ dinon, supposedly 1.2 gain, which I've always doubted as another epson 80" branded screen I have is 1.0 gain, but quite a lot brighter to the eye. Obv size is a factor for the FL but this is the case even when the projector is zoomed to 90" and projecting on both Materials at the same time. 

 

For the samples there are two ALR samples at 0.8 gain (one of those acoustically transparent) , and 1 at 1.2 gain (designed for 3d). Along with a white non ALR at 1.0. Then there are the properties of the room itself, creme walls, white ceiling. Matte paint

 

It also occurred to me that depending on where the black level and white levels need to be set for the samples that will alter the underlying screen view as well, so I'll have to ignore the comparison aspect for that test. 

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6 hours ago, usethe4c said:

Well validate manufacturers cliams to an extent, some of which are vague

Sounds to me you're trying to needlessly complicate things. If manufacturer claims are vague, look elsewhere. The reputable manufacturers will recommend the appropriate screen for your application. Just leave it at that. I use Stewart screens, have done so for as long as I can remember. For sure they will know the perfect screen from their range for your application.

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On 07/11/2021 at 7:30 AM, usethe4c said:

probably not a complete idiot on the subject.

 

👍

 

There's a fair bit of merit in what you said.   You are interested in the performance of the material after calibration.... not if you like the differences between difference materials under a single setup.

 

As long as the screen gain, and color tone suit your intended setup.... then you should be fine, and as you say some types of contrived testing could be confusing.

 

IMO probbaly the bigger thing to be "auditioning" is the pattern in the material.... which might not be clear on a small sample.

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  • 2 weeks later...
On 07/11/2021 at 7:30 AM, usethe4c said:

When you are comparing the performance of a screen sample against your current screen surface it seems perfectly valid to simply attach the sample to the current projection surface and compare it with some dark and bright content. 

 

the main problem is your projector isnt really calibrated to the multiple of samples you are checking out ? if its calibrated to your main screen but not to the swatches ? its not really a great comparison ? ie not a valid comparison ?

 

On 07/11/2021 at 7:30 AM, usethe4c said:

However I've seen people do this on the avsforum and then complain about how such and such a sample is too dark with their projector or contrast isn't as good vs their current surface so they won't be buying etc

the main problem with ALR screens are very narrow viewing angles... and yeah gain can be quite low... and yes can look quite odd compared to a plain white screen ? i for one cant stand ALR screens... and have easily ruled out their use in my setup given the variations of these have seen and what can be achieved even in your typical lounge room doing best can with what have...and whats possible.

 

On 07/11/2021 at 7:30 AM, usethe4c said:

note that I've done a fair bit of self educating online and at home with a version a i1 display pro, avs709 test patterns, hcfr, I've got a current version of Chromapure (for which I've read most of the manual) and read a lot of posts on the avsforum/curt palme forum on calibration. I haven't got very good delta e results trying to calibrate a white screen in a living room environment though (understandable) 

 

there is a fair learning curve with calibrating projectors... i have myself given it a fair shot in past and now days am just leaving it to the professional... :) you can actually achieving quite good results in a "white room" it jsut depends what else is in the room ? carpet, soft furnishings or highly reflective ? how far away from reflective surfaces  - ceiling ? floor ? even couches ? the folks that pursue the absolute go for what are "black hole" light sucking theatres... ie all and everything covered in black velvet ... this goes above and beyond any ambient light entering the theatre.. there is even jokes of watching with wearing black velvet suits :D 

 

ofcourse no matter the projector all this matters ... but there are compromises in every setup so do what best can do with the room first and be surmised what can achieve with even a conventional screen :) ...fi the draw backs of ALR screens is all too much ...

Edited by betty boop
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