The Ultimate 3D projection system: A Practical Discussion Thread - Page 79 - AVS Forum | Home Theater Discussions And Reviews
Baselworld is only a few weeks away. Getting the latest news is easy, Click Here for info on how to join the Watchuseek.com newsletter list. Follow our team for updates featuring event coverage, new product unveilings, watch industry news & more!


Forum Jump: 
 5Likes
Reply
 
Thread Tools
post #2341 of 2362 Old 07-21-2015, 01:29 AM
Member
 
zorg43x's Avatar
 
Join Date: Jan 2013
Posts: 73
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 10

We love you, BlackShark!!! Keep us reported of the prototype

Last edited by zorg43x; 07-21-2015 at 01:51 AM.
zorg43x is offline  
Sponsored Links
Advertisement
 
post #2342 of 2362 Old 07-21-2015, 04:20 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
Xtremscreen Daylight review part 2 : a visit to Xtremscreen's HQ in Strasbourg, France.


(images from Wikipedia)

Strasbourg, it's historic city center with narrow streets, old medieval houses, sweet winstubs (traditional food & wine restaurants), and it's towering Gothic cathedral in it's center,... such a great place to hang out, where we're not going today.

Xtremscreen's HQ is located in an industrial lot in the small town of Souffelweyersheim, just off the A4 highway at the outskirts of Strasbourg.

Laurent Fernandez and Franck Lapp, co-founders of Xtremscreen welcomed me, and helped me unload all my hardware.

The main focus of their showroom is a ceiling mounted rollable Daylight 0.9. Coupled with a beautiful Sony 4K laser projector, and they extended the screen far outside of the picture in order to create an optical illusion to prevent the brain from seeing the border of the screen : since the brain can no longer see the frame or the wall to contrast against the picture. It makes the picture pop so much more it's gorgeous....


ok I have to stop looking at this, it's completely outside of my price range let's go back to work.
We started working using one of their Daylight Reference 1.1 screens with a surprisingly thin but nice looking zero-edge frame.


As I said in the previous post, the Xtremscreen Daylight material keeps most of the polarization as the light bounces off the screen surface.
This doesn't matter at all for 2D use (our eyes cannot distinguish the difference between the different types of light polarization).
For active 3D use keeping polarization is interesting because it allows you to leverage more light out of LCD and LCoS projectors (LCD shutter glasses have a polarizing filter in them), but you'll have to use the manufacturer's glasses, because every manufacturer uses a different internal polarization for their projectors and glasses, and if you use the wrong combination, you'll get a completely black picture.
But for passive polarized 3D, you need more : you need the screen to maintain the polarization perfectly (more than 99% preservation). Every fraction of a percent of depolarized light will cause more and more crosstalk. And this is where the Daylight Reference 1.1 falls short. The screen is very usable, but there are lots of scenes where you can see crosstalk.
The Daylight 0.9 offers better light uniformity (I can't see any hotspot) it looks really great even though it's slightly dimmer, but it does slightly worse than the Daylight Reference 1.1 in terms of polarisation retention.

Fortunately Franck and Laurent brought samples of prototype screen material they made when they developed their screen materials. Some were mounted on a full-size screen, some were just 30x30cm samples.
One of them, a Daylight Reference 1.1 material with slightly modified formula stood out.

WOW ! The crosstalk is less than the 5% grey on the scale. This is an amazing result.
The screen behind the sample is the standard Daylight Reference 1.1, and it shows how dramatic of a difference it makes.
When I saw this, I instantly wanted to buy a screen made with this material. If you compare the whites, the greys and the black, the material looks extremely close to the Daylight Reference 1.1 in all other aspects (same gain, same clean picture).
This is significantly better than my Harkness Spectral 240 in every possible way.

Just out of curiosity we also tested samples from competitors.
Xtremscreens' main market is the high end, ambient-light resistant screen, with low hotspot and gains close to 1. The usage domain is mainly for traditional 2D and active 3D projectors which 99.9% of people use. So they do not test against silverscreens or super high gain screens.

This is Screen Innovations BlackDiamond 0.8 (and 1.4 in the little corner). These are not rated for passive 3D. SI does make a BlackDiamond material for passive 3D but it's 2.7 gain is considered too high by Xtremscreens to compete against. So it was no tested.

It was known for a while, the SI BD 0.8 and 1.4 are not suitable for polarized 3D. Again, we are not testing the SI BD 2.7 (which they claim works for passive 3D)

Here is an other competitor : DNP Supernova ambient-light resistant screen, which I believe is called the 08-85.

It's plain and simple : DNP supernova does not maintain polarization at all. (they do not claim anything regarding passive 3D, so no surprise here, just a confirmation)

So where does this leaves us :
Xtremscreen's prototype material is a winner. I want it on my screen ASAP ! Can I buy it ?
The answer is yes : I can buy it but with small restrictions.
First, I have to wait a little. The prototype material is slightly different from the official Daylight material, and it doesn't cope well with the stretchy PVC plastic support material all the other screens are made of.
The prototype material was applied to a rigid plate, they do have a full-size example screen using a similar material, and it is a nightmare to transport and mount. So after a lot of testing on how to transport such screens to customers, they finally decided not to sell screens on rigid plates : the screen has to be rollable.

Fortunately, in the last few months, Xtremscreens have been hard at work to be able to use a different, much more rigid but still flexible material for a different project based on PET plastic. They believe the prototype 3D material should work with this prototype support material but they want to test it first before selling one.
If it works, the material will be made available for everyone.
However : the prototype 3D material will only be made in limited quantity.

The material does not have an official name but because it looks so much like the Daylight Reference 1.1, I decided to call it : "Daylight 1.1, special polarized 3D edition". So if you contact them, you can use this name and they'll know which screen material you are talking about.

You also need to know that the "special polarized 3D edition" has some small differences when compared against the regular Daylight Reference 1.1 material.
The Daylight 1.1 special polarized 3D material has a slightly smaller view angle than the regular material (a little bit more hotspot), but as a result it should resist ambien light slightly better (but it's a very small difference).
The Reference 1.1 material produces so little hotspot, I'm not worried about a small increase. It should be fine.
It has a little bit more shimmering than the regular material. I couldn't see any from across the table, but if I walk up to the sample, then yes shimmering appears on the prototype sample, whereas it's very hard to see on the regular material even at close range.
It won't be a problem for me though, because at 3m, I can't see any. And even if I missed it, it would be very small, and the leap in crosstalk would be sooo much worth it.

Xtremscreen will stick to their current material for the broad Reference 1.1 screens, because it offers slightly better performance for 2D and active 3D users. They probably won't advertise this product in their showroom, or in any other showroom. So if you are interested by this product : you have to contact Xtremscreen directly (email on their website). It's a niche product, specially for "in the know" polarized 3D users.
If you are just a regular 2D projector user or use active 3D and found this thread, then you can stick with the regular Daylight line of screens (0.9 and 1.1 Reference). The "Daylight 1.1 special polarised 3D edition" is not for you.

I reserved the very first screen, I am eagerly waiting for the green light from the screen support material test. I can't wait !

If you are also interested by this screen material. Send them an email.
Pricing is not fixed, and since it probably won't be advertised : you have to send them an email to get an estimate.
If you are unsure, or if you just want more information on this screen material, do not hesitate to send them a mail anyway.
At the moment there is only a very limited production because it's such a niche product but if there is enough interest in this screen material, maybe they'll launch it into full production.

I would like to thank Laurent Fernandez and Franck Lapp from Xtremscreen for their hospitality, for their professionalism and for making such an amazing product.
(I'm the guy in the middle on the picture, the true heroes are on the left and right)

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 07-21-2015 at 05:02 AM.
BlackShark is offline  
post #2343 of 2362 Old 07-22-2015, 12:12 AM
Member
 
zorg43x's Avatar
 
Join Date: Jan 2013
Posts: 73
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 10
Excellent report, Blackshark!

I am very surprised, that the improved 1.1 gain sreen keeps polarization better than the HS 240 with more than twice that gain. And less than 5% crosstalk is an excellent result even for silver sreens I guess!



Damn, now I recall that I should have sent you a 1x1m sample of a cinema silver sreen from MW (gain >2), that we can have a reference point on polarization retention. I'll PM you later...
zorg43x is offline  
post #2344 of 2362 Old 07-22-2015, 02:59 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
If you have a polarized dual-projector setup, you can download the test pattern and test it directly yourself without having to send screen samples across the world.
The only thing yout have to be careful about is that I use linear polarization, that's all.
Quote:
Originally Posted by BlackShark View Post
Download : PNG FullSBS (3840x1080)
Download : MPO FullHD (thanks RBTO)

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 07-27-2015 at 11:42 PM.
BlackShark is offline  
post #2345 of 2362 Old 07-22-2015, 11:38 PM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
Quote:
Originally Posted by zorg43x View Post
I am very surprised, that the improved 1.1 gain sreen keeps polarization better than the HS 240 with more than twice that gain. And less than 5% crosstalk is an excellent result even for silver sreens I guess!
5% grey crosstalk for such a test is an extremely good value. According to the various pictures of other screens I've seen on the internet, silverscreens top at about 10% grey.

Notice that's a "grey" value (visual measurement) not a measurement by a light-meter. If you wanted to translate this into absolute crosstalk, there are a few operations you need to take into account : there is the gamma curve (50% grey is not 50% light) then there is the software gamma correction of the projectors which I have not measured, and then you have to take into account that the greyscale in the chart is shown in both eyes. So the calculation would be a bit messy.

If you were to measure the crosstalk with a light-meter, silverscreens and this prototype would be within the final 1% of crosstalk, and I guess the regular Xtremscreen Daylight Reference 1.1 would be somewhere between 2~5% crosstalk.
Indeed, a few fractions of a percent crosstalk make that much difference on screen.

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)

BlackShark is offline  
post #2346 of 2362 Old 07-26-2015, 02:20 PM
Member
 
RBTO's Avatar
 
Join Date: Jan 2008
Location: Idaho
Posts: 152
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 11
Here's the MPO version of Blackshark's updated test image. The MPO file is a jpeg type file with both left & right images in a single file. If loaded onto a thumbdrive or SD card, it can be used in many newer TVs to show the 3D image on screen. Some BD players also have the capability to take a thumbdrive or SD card with MPO files and generate the full HD 3D HDMI signal from it. Credits to Blackshark of course for the pattern. L&R alignment isn't applicable since TVs achieve (at least they should achieve) pixel perfect alignment between the images.
While active 3D sets should get theoretically better crosstalk figures than passive sets, crosstalk can exist due to imperfections in the glasses and timing between the set and the shutter glasses, so Blackshark's test pattern is valuable for checking both types (if you're interested in doing that).

Note: Since MPO files aren't listed in the acceptable uploadable file types, I don't think I can post it as such, but here's the workaround. I changed the file extension to jpg which will upload. If you download this file, just change the extension back to mpo and it should work. Actually the mpo will open as a jpeg with some viewers and show just the left image, but the mpo has both images and on the proper devices will produce a 3D image.
Attached Thumbnails
Click image for larger version

Name:	BlackShark_alignment_FullHD.jpg
Views:	18
Size:	818.5 KB
ID:	852482  

Last edited by RBTO; 07-26-2015 at 02:55 PM.
RBTO is offline  
post #2347 of 2362 Old 07-27-2015, 12:22 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
Actually, passive TVs have a 1 pixel offset and only half the lines. The pattern will probably still be interesting to analyse how well the resolution interpolation filter works inside the TV.
I tested it with my passive Zalman 22" monitor (same technology as LG's FPR), I get about 10% grey crosstalk if I'm exactly at the right spot (but the spot is super narrow)

I noticed you used the previous version of the pattern for the mpo file. Can you do it again with the latest (hopefully final) version ?

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 07-27-2015 at 12:35 AM.
BlackShark is offline  
post #2348 of 2362 Old 07-27-2015, 06:03 PM
Member
 
RBTO's Avatar
 
Join Date: Jan 2008
Location: Idaho
Posts: 152
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 11
Quote:
Originally Posted by BlackShark View Post
Actually, passive TVs have a 1 pixel offset and only half the lines...........

I noticed you used the previous version of the pattern for the mpo file. Can you do it again with the latest (hopefully final) version ?

You're quite right Blackshark and I probably should have said "near" pixel perfect alignment. Interestingly, when you see the images your eyes adjust to that slight vertical misalignment and you see an aligned image with dark raster lines between the active lines (one of the failings of passive 3D sets). Of course, the viewed image on passive sets is only half the vertical resolution because it makes use of only 540 lines per image (L&R). I have noticed some aliasing on my 3D set in the fine details so there are some (minor) errors introduced when the full HD image is separated into the corresponding 540 line images. Some of this might be attributed to bright image details bleeding through which would show up on the alternate lines which otherwise should appear black to a given eye (crosstalk nonetheless).

Sorry, I grabbed the wrong file when I attached it. Here's the mpo using your latest test image. Again, it's attached with a jpg extension - change that back to mpo after you've saved it.
Attached Thumbnails
Click image for larger version

Name:	BlackShark_alignment_SBSFull.jpg
Views:	16
Size:	626.7 KB
ID:	855042  

Last edited by RBTO; 07-28-2015 at 07:38 AM.
RBTO is offline  
post #2349 of 2362 Old 07-27-2015, 11:42 PM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
Done !
I uploaded the mpo file to my server and added the download links. Thanks

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)

BlackShark is offline  
post #2350 of 2362 Old 07-28-2015, 07:57 AM
Member
 
RBTO's Avatar
 
Join Date: Jan 2008
Location: Idaho
Posts: 152
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 11
Quote:
Originally Posted by BlackShark View Post
Done !
I uploaded the mpo file to my server and added the download links. Thanks
Great! In meantime I submitted a suggestion to the webmaster to add mpo to the list of acceptable uploads since mpo files are a good way of sharing still 3D content (a lot can be found on the web). I use my 3D system and TV from time-to-time as a 3D slide show and the content is drawn from mpo files on a thumbdrive (I happen to have a digital 3D still camera which I use to shoot those shots - you can get some amazing still 3D content which works well on a 3D projection system for some jaw dropping 3D).

Thanks Blackshark for all your excellent input to this forum!
RBTO is offline  
post #2351 of 2362 Old 08-24-2015, 10:05 PM
Newbie
 
Join Date: Aug 2015
Posts: 5
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 0
Reading so many conversations about ambient-light resistant screens for passive 3D, I'm thoroughly confused! I plan to build a home theater in a basement with no windows. It could be pitch black, or we can have lights on dimmer switches too. I do want eye-popping, depth-defining 3D, so I probably still want a silver screen, right? Recommendations?
Ted Miller is offline  
post #2352 of 2362 Old 08-25-2015, 04:03 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
If you use a dedicated dark cinema room, you won't be bothered by Omega's high reflectivity filters, so you have the choice : you can use polarised fitlers or Omega filters
Check the Omega Optical thread Official Omega 3D passive projection system thread (Motorman45 is en employee from Omega Optical)

Omega is cheaper (no need for special screens, you can use any screen you want), is simper to set up and is crosstalk free (you get amazing 3D).
The problem is that colour accuracy is hit and miss. It depends on the inner workings of the projectors, stuff that is never advertized so you have to buy it and try to know.
It either provides good colour or it doesn't and there is absolutely nothing you can do to fix it.

Polarized is more consistent but is more expensive, there are more parts that can cause issues, crosstalk is always present and you have to get the right parts to make sure you keep crosstalk to a low enough level. (and choosing the right screen is a big part of that)

Since you are worried about silverscreens, it means you are heading for polarized.
Until a few weeks ago, high quality cinema-grade silverscreens was pretty much the only option if you want low crosstalk with polarized 3D.
But silverscreens have defining characteristics which are often considered as really bad : silverscreens are high gain and highy directive. So they have a very narrow view angle : they have a strong hotspot. (the on-axis center of the screen looks extremely bright, but the edges look dark).
You can use a curved screen to try and reduce the issue. But there is no magic bullet. Curved screens are even more expensive and come with their own issues especially in a home environment.
Silverscreens also tend to be designed for large theaters where the audience sits at least 10 metres away from the screen (and the best seats are much farther). When you use such a screen at close range in your home, there will be visible structure and shimmering effects.

Because of these issues, silverscreens are considered really bad for 2D, and having owned and use one for over 4 years, I have to agree : my white wall provides a cleaner picture than my Harkness Spectral 240 silverscreen.
In the last few years, screen manufacturers have introduced intermediate compromise screens that attempt to provide a better balance between 2D and 3D usage, but they are far from ideal : if the visible structure and shimmering has been reduced, they will never compete with 2D screens and these screens are still high gain and have a narrow view angle (they hotspot).

The new ambient light resistant screens is just a lucky find. These manufacturers weren't really looking for this characteristic, it just happens that it was a side effect of the ambient light resistance technique they use.
The goal of these screens is to provide the most even reflectivity as possible while covering the typical view angle where people sit (get a good picture for the couch), and then cutoff the reflectivity as sharply as possible for higher angles so that the screen rejects the most harmful light coming from the ceiling and the walls close to the screen.

Not all ambient light resistant screens offer good polarized performance. To my knowledge there are only 2 that are suitable for polarized 3D :
-Screen Innovations BlackDiamond 2.7 (it's very high gain) I have not tested it but Rdjam has one. He did not publish pictures but has reported in an other thread that it works well.
-Xtrem Screen Daylight 1.1 (standard "reference" model works but has barely acceptable polarized characteristics, the "special edition" protoype has the most amazing ability to maintain polarization I have ever seen, I am really looking forward to test the full scale screen)

For the Xtrem Screen Daylight 1.1 special edition for polarized 3D, I am still waiting for Xtrem Screen's lab tests.

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 08-25-2015 at 04:07 AM.
BlackShark is offline  
post #2353 of 2362 Old 08-25-2015, 11:37 AM
Member
 
wanderer's Avatar
 
Join Date: Jun 2001
Location: Pacific Northwest
Posts: 89
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Blackshark - thanks for posting your excellent test and alignment pattern. I've used the .mpo version on my passive setup and I really like how we can now subjectively evaluate the polarization retention of both left and right, basically at the same time. The L and R markers for alignment are also great - I found my bottom right corner was out big a pixel or so which was hard to spot using a normal crosshatch pattern. Thanks too to RBTO for making it into an mpo file!

I have the Stewart 5D and it's below the 5% level for sure for linear passive. I've had a largish sample of the BD 2.7 and that too would be below the 5% marker as well as the 5D and BD 2.7 are very close to each other in performance. I put some thoughts on these in the 3D screens thread here on AVS a while ago.

What this test pattern really showed me though was that one of my linear polarizers at the projector might be going bad. The right eye filter is easily below 5%, but the left eye filter looks like it's at about the 7% or so mark. Might be time to order some new polarizers as the ones I've got are coming up on 2 years of age.
wanderer is online now  
post #2354 of 2362 Old 08-27-2015, 11:48 PM
Newbie
 
Join Date: Aug 2015
Posts: 5
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 0
I appreciate the detailed reply, Blackshark. I'll research the BlackDiamond and probably read your report from Strasbourg 3 times now. Do you think using an LED projector would make any difference in the quality with ambient light-resistant or silver screens, for better or worse?

I was completely sold on the Omega system -- probably read every mention on AVS Forum -- but contacted Omega Optical and learned it's not compatible with LED projectors because they lack full-spectrum color balance. We want to buy a pair of LG PF1500. I was strongly considering the BenQ W1070 over some Optomas before the PF1500 came out with a longer lamp life, TV tuner and other features we never expected under $1,000. Since we don't have the means to upgrade our technology often, setting up this theater is our mid-life crisis shebang! I'm still planning on a Geobox 501 (or a lingering Airflex 5D) but now looking into RealD-compatible circular polarization filters with the ubiquitous glasses. Maybe I can charge the neighborhood kids admission to pay for an upgrade (hope the FBI didn't see that).
Ted Miller is offline  
post #2355 of 2362 Old 08-28-2015, 05:56 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
Quote:
Originally Posted by wanderer View Post
I have the Stewart 5D and it's below the 5% level for sure for linear passive. I've had a largish sample of the BD 2.7 and that too would be below the 5% marker as well as the 5D and BD 2.7 are very close to each other in performance. I put some thoughts on these in the 3D screens thread here on AVS a while ago.

What this test pattern really showed me though was that one of my linear polarizers at the projector might be going bad. The right eye filter is easily below 5%, but the left eye filter looks like it's at about the 7% or so mark. Might be time to order some new polarizers as the ones I've got are coming up on 2 years of age.
5% grey crosstalk is an amazing result for silverscreens. I remember reading the polarized extinction ratios of Stewart screens (back when they published it on their old website) the figures they were mentioning didn't point to such a drastic performance difference with the Harkness Spectral 240.
I am surprised they improved so much. I expected the Stewart screens to achieve about 10% grey (slightly better than then Harkness)
Unless the Stewart materials have a preferred direction and perform better following one angle rather than the other one ?

7% mark ? Do you mean somewhere between 5 and 10 % or did you mistake the 5% steps for 2.5% steps ?

Quote:
Originally Posted by Ted Miller View Post
I appreciate the detailed reply, Blackshark. I'll research the BlackDiamond and probably read your report from Strasbourg 3 times now. Do you think using an LED projector would make any difference in the quality with ambient light-resistant or silver screens, for better or worse?

I was completely sold on the Omega system -- probably read every mention on AVS Forum -- but contacted Omega Optical and learned it's not compatible with LED projectors because they lack full-spectrum color balance. We want to buy a pair of LG PF1500. I was strongly considering the BenQ W1070 over some Optomas before the PF1500 came out with a longer lamp life, TV tuner and other features we never expected under $1,000. Since we don't have the means to upgrade our technology often, setting up this theater is our mid-life crisis shebang! I'm still planning on a Geobox 501 (or a lingering Airflex 5D) but now looking into RealD-compatible circular polarization filters with the ubiquitous glasses. Maybe I can charge the neighborhood kids admission to pay for an upgrade (hope the FBI didn't see that).
LED or bulbs shouldn't make much of a difference regardless of the screen technology you choose. However these LED projectors tend to provide only limited amounts of light. LG is pushing hard for higher and higher lumen output though.
For a 100" screen or higher I strongly recommend projectors with 2000 lumen : remember you will be throwing away half of the light when you put polarising filters in the beam. I'm not sure LG's affordable LED projectors are up to the task yet.

Let there be no doubt : Omega is simpler and much cheaper : remember no silverscreen needed, you can go with much cheaper screens, even a white wall). And if you choose DLP projectors you should get better colour accuracy than with LCDs.

If you go with polarized, then I recommend going with linear polarization. You'll get lower crosstalk. The glasses are not compatible with RealD but I found a local (French) retailer that uses exactly the same shape of glasses as RealD but with linear filters for 3€ per unit. I bought a pack of 10 they work well (you can see them spread everywhere on the pictures from my trip to Xtrem Screen). You should have no problem finding the glasses you need with linear filters. Just make sure you double-check the polarisation angles used : some glasses use the most common 45/135° "through the nose" configuration, some use the IMAX 0°/90° configuration.

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 08-28-2015 at 06:00 AM.
BlackShark is offline  
post #2356 of 2362 Old 08-28-2015, 04:00 PM
Member
 
wanderer's Avatar
 
Join Date: Jun 2001
Location: Pacific Northwest
Posts: 89
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Blackshark - I took a photo today to demonstrate the 5D displaying your test image. The camera is an old one and pretty terrible at low light levels, and capturing a ~5% image behind glasses isn't that easy either . The normal orientated glasses image just shows the normal L and R glass eye images. The rotated glasses image shows the same L\R filters at the projector, but now in a "left" eye view and to me the ~5% performance looks the same. That also tells me it's probably the L side projector filter that's the issue as it's levels are a bit higher. I'll know for sure once I get some new projector filters - the ones I have now are plastic linear filters. They've just performed so well I never felt the need to upgrade.
Attached Thumbnails
Click image for larger version

Name:	003.jpg
Views:	20
Size:	187.5 KB
ID:	912794   Click image for larger version

Name:	006.jpg
Views:	22
Size:	201.6 KB
ID:	912802  
wanderer is online now  
post #2357 of 2362 Old 08-28-2015, 10:25 PM
Newbie
 
Join Date: Aug 2015
Posts: 5
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 0
Quote:
Originally Posted by wanderer View Post
Blackshark - I took a photo today to demonstrate the 5D displaying your test image. The camera is an old one and pretty terrible at low light levels, and capturing a ~5% image behind glasses isn't that easy either . The normal orientated glasses image just shows the normal L and R glass eye images. The rotated glasses image shows the same L\R filters at the projector, but now in a "left" eye view and to me the ~5% performance looks the same. That also tells me it's probably the L side projector filter that's the issue as it's levels are a bit higher. I'll know for sure once I get some new projector filters - the ones I have now are plastic linear filters. They've just performed so well I never felt the need to upgrade.
Wanderer, by 5D do you mean the Airflex 5D? Wondering how you like it and if you can still get (or need) firmware upgrades for it. I understand it's a relabeled Geobox 501?
Ted Miller is offline  
post #2358 of 2362 Old 08-29-2015, 01:31 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
@Ted Miller
He means Stewart 5D (a silverscreen)
I own a Geobox 501, it's a nice demultiplexer and I like how easily I can convert many formats for dual projectors.
But it's expensive. I had to buy mine direct from VNS taiwan and pay the import taxes which made it even more expensive. It ended up costing me almost 1000€.
I could have bought a much less expensive demultiplexer if I only wanted simple hdmi1.4 resolutions though, the true reason why I bought was to ensure I had the bandwidth to do stereo 1080p60 for PC gaming with the DisplayPort input.

@wanderer
Your picture looks really clean, indeed.
I agree taking a crosstalk picture with a crappy camera is hard. On my phone I can't even see a proper preview because it requires the use of long exposure night mode, so I have to shoot blind and I never manage to get the crosstalk to look exactly like what I see, because I never know if I'm holing the glasses at their perfect angle. The picture always show about 5% more grey than the best I can see with my eyes.

I use glass reinforced filters so they have a much longer lifespan. Their heat resistance is rated for 5000 Lumen projectors, so I'm not worrying about my 1800 Lumen (advertized) projectors.
The one thing that stands out on your picture is the colour accuracy is much better than on mine. I believe the colour accuracy issues I encounter are because my 3LCD projectors have crossed internal polarisation between the primary colours.
Can you remind me what type of projectors you are using ?

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; 08-29-2015 at 01:50 AM.
BlackShark is offline  
post #2359 of 2362 Old 08-29-2015, 03:04 PM
Member
 
wanderer's Avatar
 
Join Date: Jun 2001
Location: Pacific Northwest
Posts: 89
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Quote:
Originally Posted by Ted Miller View Post
Wanderer, by 5D do you mean the Airflex 5D? Wondering how you like it and if you can still get (or need) firmware upgrades for it. I understand it's a relabeled Geobox 501?
Hi Ted, as BlackShark mentioned it's the Stewart 5D screen that I was referencing. I did however have the Omega LCD system previously, and also have a no longer used Geobox 201. In my case the projectors I use have great lens adjustment for up\down\left\right, so I was able to stack them and get near perfect alignment and didn't need a 501 as a result.

How big do you want your screen size to be? Getting an acceptable level of brightness really depends on a) screen size, b) gain factor of screen, c) type of filters used (light loss) and d) your projector placement distance and its light output. Getting acceptable color balance is a different question again. How picky are you about color?

Some good 3D screen reading can also be found here on AVS: Discussion - Screens for 3D Projection. My contribution in there is post 315.

Last edited by wanderer; 08-29-2015 at 09:21 PM.
wanderer is online now  
post #2360 of 2362 Old 08-29-2015, 03:41 PM
Member
 
wanderer's Avatar
 
Join Date: Jun 2001
Location: Pacific Northwest
Posts: 89
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
Quote:
Originally Posted by BlackShark View Post
@wanderer
Your picture looks really clean, indeed.
I agree taking a crosstalk picture with a crappy camera is hard. On my phone I can't even see a proper preview because it requires the use of long exposure night mode, so I have to shoot blind and I never manage to get the crosstalk to look exactly like what I see, because I never know if I'm holing the glasses at their perfect angle. The picture always show about 5% more grey than the best I can see with my eyes.

I use glass reinforced filters so they have a much longer lifespan. Their heat resistance is rated for 5000 Lumen projectors, so I'm not worrying about my 1800 Lumen (advertized) projectors.
The one thing that stands out on your picture is the colour accuracy is much better than on mine. I believe the colour accuracy issues I encounter are because my 3LCD projectors have crossed internal polarisation between the primary colours.
Can you remind me what type of projectors you are using ?
I think my photos too came out a bit higher % wise than what I see on the screen. It's definitely not easy taking good photos!

Thanks for noticing the color accuracy - each projector has a unique 3D lut calibrated to REC.709. My setup is 3D source > HDMI 1x2 splitter > Lumagen Radiance Mini 3D (one for left, one for right) > Panasonic AE4000 projectors > Stewart 5D. The Panasonic projectors have a Cinema mode that far exceeds the REC.709 triangle, Calman and a C6 meter bring that back to REC.709 with a 3D lut applied in the Radiance Mini for each projector. Each 3D lut is measured with the projector filter in place and lens of the glasses in front of the C6 sensor, so each eye has a 'calibrated' output. The projectors are also light balanced as well as part of the calibration so the light levels are the same across both of your eyes. The original light output from the Panasonic projectors is completely unpolarized, I believe due to the smoothscreen technology in use.

I now have 3 different types of 3D linear glasses and they all measure differently with Calman in regards to what they do to the light and color balance (reduce R,G or B) as well as how they perform relative to polarization retention and ghosting. I've been thinking about posting these findings for a while but wanted to test out a few more pairs first. I'm now thinking that the projector linear filters will be a similar story - some manufacturers will have a good design and won't mess with the R\G\B output too much, others will mess with it much more.

If you decide to create some more test images in the future, a 0-20% level test pattern image with 1% stepping blocks would be great at measuring what the actual polarization retention is. This could be used as a visual measuring tool for the combinations or filters, glasses and screen materials.
wanderer is online now  
post #2361 of 2362 Old Yesterday, 10:33 AM
Advanced Member
 
BlackShark's Avatar
 
Join Date: Jun 2010
Location: Montpellier, France
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 18
I just read this article from projection central about ambient light rejecting screens http://www.projectorcentral.com/ambi...sion-PolarStar.
It claims the Elite Prime Vision Polarstar retains 92% light polarisation and thus is compatible with passive polarized 3D.
This sounds low to me. I have a hunch it will have crosstak similar to my XtremScreen Référence.

I am trying to find the relationships between polarisation retention figures, extinction ratios, and the visual grey equivalent crosstalk from the crosstalk chart I made.

I have heard for a long time about gamma curves and that the relationship between the grey scale and the light intensity not being a linear one.
But the problem is : when searching on the internet about what this relationship between input and output light intensity was, I keep reading "Gamma curves are for correcting the non-linearity in CRTs, LCD work differently". And how LCDs relationship between input and output light intensity is never explained.
But then I see that the computer industry uses sRGB standard which includes a systematic gamma correction factor of 2.2 because it's the average of how CRT monitors used to behave when the standard was set. I have to deduce that any newer display technologies since must artificially introduce a gamma curve of 2.2 to reproduce the behaviour of CRTs, because they're fed inputs designed for CRTs.
And if I look at my Epson's gamma correction settings : it appears to match this because the default gamma value is 2.2.

So if I understood correctly, all computer images are pre-corrected with a gamma correction factor of 2.2.
When I take a picture with a digital camera, when the camera creates a JPEG file, it will apply a correction factor of 2.2 so that the picture looks good on a standard sRGB CRT monitor.

However when I use my computer paint tool and draw something with 50% grey (128R 128G 128B), I am not taking the gamma correction factor into account, so I am not painting 50% intensity on my screen but I am actually painting 0.50 ^ 2.2 = 21.7 % light intensity.

Let's try and do some math.
My current ambient light resistant screen : Xtrem Screen Reference 1.1 has a visual crosstalk of 30% grey on my chart.
0.30 ^ 2.2 = 0.07 light intensity.
The greyscale also needs to be taken into account, since it is visible in both eyes, it's intensity is actually increased by it's own crosstalk coming from the other eye.
We'll assume both projectors have the same light intensity.
Crosstalk = scaleIntensity + scaleIntensity*Crosstalk
so,
Crosstalk = scaleIntensity/(1-scaleIntensity)
So the crosstalk measured visually is actually : 0.075 = 7.5 %.
The Extinction ratio is 92.5/7.5 = 12.3:1 Ok this number shows how bad it actually is since most actual silverscreens are above 100:1 (typically 100:1 to 150:1)

Result of the camera measurement (visually it's about 5% grey darker) :
XtremScreen Reference 1.1 (standard model, not the special 3D one)
Visual camera Xtalk : 30% grey => 92% polarisation retention, 12:1 Extinction ratio
The polarisation retention is 92.5%, ok so my XtremScreen Reference 1.1 has the same amount of crosstalk (with the camera bias) as the claimed (ideal) Elite Prime Vision Polarstar.

Harkness screens Spectal 240

Visual camera Xtalk : 15% grey => 98.5% polarisation retention, 66:1 Extinction ratioOk that's shockingly lower than what is claimed (130:1 peak)

Let's do the reverse calculation with my Spectral 240 (peak extinction is rated at 130:1), and see where we end up with the visual crosstalk.
Extinction = (1 - Crosstalk) / (Crosstalk)
so
Crosstalk = 1 / (1 + Extinction) = 0.0076 (99.24% polarisation retention)

Apply the scale intensity crosstalk :
scaleIntensity = Crosstalk / (1+Crosstalk) = 0.007575
let"s apply the gamma compensation : 0.007575 ^ (1/2.2) = 0.1086 (11% grey at peak).

Considering how every time I try tro take a picture , I end up measuring about 5% higher grey than what I can see with my eyes. It's actually quite close to what I am getting.
These calculations actually show how fast the figures change just to try and gain a few percents of visual crosstalk.

As a comparison : a 5% grey visual crosstalk actually means : 0.14% crosstalk (99.86% polarisation retention), or 713:1 Extinction ratio.
I have yet to find a screen manufacturer that claims such crazy high values even under ideal conditions. These values are close to the extinction ratios of polarizing filters. In theory, it wouldn't be possible to do any better since you'd be hitting the max performance of glasses. However, I remember seeing extinction ratios ">1000:1" on filters and glasses. So maybe it's just that it becomes hard to measure precisely super low light intensities even with professional light-meters.

I am puzzled.
When calculating the visual crosstalk from the theoretical best case extinction ratio, I obtain something believable.
When calculating the extinction ratio from the visual crosstalk, I obtain huge differences

EDIT:
Just had a look at the Extintion ratio curve published by Harkness.
I just noticed how sharply the extinction ratio drops with angle.
The locaiton of the crosstalk test is actually quite far down from the ideal light bounce on the screen : it would explain in large part the huge difference between what I measured visually and the theoretical maximum extinction ratio.

Passive 3D, forever !
My Full-HD dual-projector passive polarised 3D setup. (really out of date ! I need to update it some day...)


Last edited by BlackShark; Yesterday at 10:53 AM.
BlackShark is offline  
post #2362 of 2362 Old Today, 10:18 AM
Member
 
wanderer's Avatar
 
Join Date: Jun 2001
Location: Pacific Northwest
Posts: 89
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 12
BlackShark - I think the digital camera image captures might be running into a polarization issue within the camera. That is, what our eyes see on the screen isn't captured that well with the digital image at those % image points.

On the screen polarization retention ratios, what you are seeing isn't surprising to me. Manufacturers can claim whatever % ratio they like, but in reality it might be a very different story. For the Harkness 240 - isn't that also real cinema material? If so, the black level in the theater isn't as low as what you'd get at home, which means the black level might have been higher (~10% level on your chart) when they made their measurements and calculations. I'm attaching a Stewart 5D whitepaper pdf which talks about the differences they found in cinema vs home, as well as their claim of 140:1 extinction ratio. With many screen materials the manufacturer just rates it as being '3D passive compatible' with no further explanation. With the Elite Cinegrey 5D material they claim that it retains 88% polarization and is suited for passive 3D - I don't think you'd agree with that!

I just trust my eyes at this point. I want near zero levels of ghosting and I think we've found a few screens now where that's a reality.
Attached Files
File Type: pdf Silver5D_WP.pdf (91.6 KB, 1 views)
wanderer is online now  
Sponsored Links
Advertisement
 
Reply Digital Hi-End Projectors - $3,000+ USD MSRP

Tags
Sony Vpl Hw50es 3d Projector



Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off