Dual projectors, choosing screen and polarisers.

[BlackShark]

That's it ! I've finally decided ! i'm buying my dual projector system next week.

I am planning to use two EPSON EH-TW3500 LCD projectors (european version of the Epson Home-cinema 8100)
I have chosen to go first with a very cheap silverscreen material (probably a Peroni superscreen) so that I don't loose much money when a screw it up (which will happen, it's my first projection system ever), and then I'll upgrade for a higher grade and more expensive screen a few weeks/month later once I'm used to manipulating a silverscreen safely.


I now need to find my filters to use with these projectors and I'm aiming for high quality and durable polarisers.

I do not know what to choose. I have read that LCD projectors can use special "stereopol" filters that keep much more light than traditional polarised filters but I do not know where to buy them.
Which manufacturers do you know ? do you recommend ?

I would be using Linear polarisation at first because there is less ghosting, however If I were to buy a super high quality screen later (from Harkness for example) I would like to know about a possible upgrade. Can stereopol linear filters be transformed into circular polarisers by adding a simple 1/4 wave retarding filter or do you absolutely need a circular filter (I think they are very expensive).

[Likay]

It's a well thought decision!
I don't know if i can add some info you don't already know by now though..
However i can give some info about later revisions of stereopol filters. The ones i have are from former silverfabric and have a throughput of 74% and 75% (according to the enclosed paper). Another user of those had more than 80 (85%?, i just recall it was significantly higher than mines) of light throughput. However i've heard rumourwise from one guy who followed my recommendations to get stereopol filters that the filters from advisol aren't too good (low lightthroughput ~65% and lots of airbubbles in the filters...). I've planned to make more tries the diy route making my own stereopol filters (know more today than then) but lacks time and always has other things to do. I'll post results if/when i have any.
The stereobrightfilters are cracked though (they are simple quartewaveplates aligned at 45° and 135°!!! ) gives in pure version circular polarization and works directly with real-d glasses. Support for stereobright and gamedrivers is poor though but stereoscopic player plays it excellently. The solution ghosts worse than even circular polarization but somehow is quite decent anyway because of the insane light throughput (no lightlosses or very minor at all what i could see...) and the insanely cheap filters (qw-retarders for projectors and real-d glasses).
Comparison between linear and circular: If using high quality filters for both circular and linear polarization you'll always see ghosting in high contrast situations using circular while you really need to look for it when using linear.

Can stereopol linear filters be transformed into circular polarisers by adding a simple 1/4 wave retarding filter or do you absolutely need a circular filter (I think they are very expensive).

It works (tried myself). However you'll get slight reflectionissues that will cut away a small amount of light. It's no big issue and if quarterwaveplates could be found with adhesive layers this would be minimized as well. Generally circular filters are a tad more expensive than linear but not too much in the pricerange of stereopol filters. If you try both kind of filters during your "burn in" i have a feeling you'll finally settle for linear anyway.

A recent similar thread at iz3d with some more lines: http://forum.iz3d.com/viewtopic.php?p=21763" onclick="window.open(this.href);return false;

I'm sorry i don't know where to get quality stereopol filters yet though.

[BlackShark]

What do you mean with "former silverfabric" ? are they no more ?

The Silverfabric website still advertises 70% transmission on the SPAR filters, however Advisol lists silverfabric as an Advisol filter reseller. I'm lost.

Is Advisol making the filter or do they only own the patents and then Silverfabric makes the filter ?

Also about prices... all the websites have removed any mention on the filter prices (shame) I'll have to write mails to know their prices.

[Likay]

I'm lost as well.
About silverfabric: That's a new one! I checked and silverfabric indeed exists (in the former well recognized shape as well, think the url-name changed though). I had the impression they once gone/changed name to awater3d (Monica Awater was my contact at Silverfabric when i got my rig to confuse even more...). I guess the only thing is to contact them.
The pricerange of a pair of spar-filters is close to getting one extra projector....

[BlackShark]

Alright I'll write these e-mails to every one of them tomorrow. I'll also have to write to Peroni and Harkness for the screen.
I'll keep this thread updated as a proceed with my purchases.

[BlackShark]

Silverfabric sent me their prices. well I was expecting the SPARs to be expensive but wow I mean they are REALLY expensive, and they don't do the 75% anymore, only 65% so I think they're not workth it anymore. I'll fall back to much cheaper more conventional filters. I'll still take the Silverfabric reinforced filters so that I know I get a durable high quality product though.

[tritosine5G]

...well, my shutter rig might become the brighter anyway.
http://readalert.atw.hu/THE_ULTRA_HIGH_GAIN_SCREEN.pdf

I'll either put a static iris inside, or something better, but 50% of lumens will be traded for better contrast.

Also there will be a white screen in front of the silver for 2d use, so I can use non eco mode 1100 lumen ~ 3000 contrast, thats ~ 800 in eco mode, just ideal for movies.

~ thats pretty decent dual purpose imho. Also crash27 over iz3d forums said something like he wont need his dual pj rig anymore now that iz3d works with 120hz dlp.

[Likay]

Parabolic screens have their caveats as well. Only one user will have the chance of being in the screens hotspot (those screens works more or less as a mirror in a telescope).
Myself i'm curious for a slightly curved screen but in my case the curvature is just going to be enough to get rid of the small amount of hotspotting i have. Which means a very little bend.
On the other hand you'll fry your eyes and gets a real sunburn using a dual pj rig with such screen as above! (this line is not to be taken seriously. )

[tritosine5G]

... you are right about the limited sweetspot, but with shutters you dont have many glasses to pass around either.

Also I always forget about something. Some months ago I read a paper by an LCD engineer guy, he was asked about this motionplus 240hz stuff (the interpolation deal) , why its necessary and so on.
It was about the usual LCD motion blur , but he had a very interesting remark: inserting a black frame inbetween the frames is actually _GOOD_ for your eyes!! ( ... how reminescent of shutterglasses hm hm )

I dont recommend this screen for DLP link tho, that white frame once a while sounds scary.