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Discussion Starter · #1 ·
Hi, Folks!


With a Qualia on the way, I'm considering the possibility of adding an ISCO 3 lens and going 2.35:1. Knowing that the ISCO 3 pincushions without using a curved screen, I'm wondering what degree of screen curvature would be necessary to eliminate the pincushioning. The huge downside of my place is that I don't have a dedicated theater, so less curvature will be a lot less objectionable in my living room/home theater. Can anyone suggest some numbers for proper screen curvature to eliminate pincushion distortion with the ISCO 3?


Thank you very much!

MarkF
 

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Mark


The pincushion on the Isco 3 totals 1 to 1.5" at most.

Split even top/bottom you are talking .5"

You will never notice this unless displaying a test pattern and this will be masked

by the screens black boarder.


I dont recommend a curved screen in your situation. It adds complication.

Most of us using a curved screen have no more then a few inches of total curve. I think I am at 9" while others are at 6" or less. I think the proper term used by the screen manufactures is cord depth.

My pincushion is perfect on the top but because my curve is rather deep ( I think Im over corrected ) I have a little PC on the bottom.


I think Dennis Erskine may be able to add further information. I think he has installed several of these systems in different situations giving him the most experience.
 

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Discussion Starter · #4 ·
Hi, Folks!


Alan: Thank you very much for the feedback, and also for the specific results! I've been admiring the screenshots you've posted of your setup, and I'm very impressed - great job! I do wish that I could ignore the pincushioning, but the problem is that I'm an HTPC fan, and every time I bring up the desktop, I find the geometry distortion issues to be objectionable (from prior experience with the ISCO 2 and two generations of the Panamorph). I guess that we've all got our personal problems! ;)


Dennis: As Alan said, I know that you're the man when it comes to high-end home theater design! I'm not sure what sorts of parameters you would need on the lens. For what it's worth, I'll be using the long throw version of the Qualia's lens. The projector's mount location requires the use of vertical lens shift, but that hopefuly won't be a factor.


The range of screens that the Qualia should be able to support with the ISCO 3, based on my projector throw distance, is anywhere from about 50x117" to 66x155". With my current G15, I'm using a 16:9 screen size of 66x117" at a viewing distance of ~1.2 screen widths. If specific technical information on the lens is required from Sony to be able to quantify the curvature, please let me know, and I'll try to dig it up. Thanks very much for your response!


Cheers!

MarkF
 

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Discussion Starter · #6 ·
Hi, Dennis!


The throw distance will be 310" (to the front of the Qualia's lens, not the ISCO). For now, let's assume a screen that's roughly equivalent in area to my current 16:9 screen (compensating a bit for the light loss from the ISCO) - perhaps 55"x129". I'm still trying to decide what the actual screen size should be, but that should provide a useful starting basis for the calculations that will get me in the right ballpark. I'm assuming that the curvature will have a roughly linear relationship with the screen width, given a fixed throw distance, so knowing this starting point, I should be able to compute the actual "rise" for whatever screen I actually choose.


Thank you again!

MarkF
 

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Discussion Starter · #8 ·
Hi, Dennis!


I'll be using the VPLL-ZP550 long throw "1.4" lens, with a focal length that varies from 44-61mm. Thanks again!


Cheers!

MarkF
 

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Discussion Starter · #10 ·
Hi, Dennis!


Just to make sure that I understand the consequences of these numbers, does this represent the forward displacement of the right and left edges of the screen that's necessary to yield no pincushioning, or does this represent the amount of pincushioning that would be visible on a flat screen (i.e. 1.8" of pincushioning on the top and the bottom of the screen)?


I really appreciate your taking the time to compute these numbers, and in helping me to understand all this! Thank you very much!!!


Best Regards!

MarkF
 

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Discussion Starter · #11 ·
Hi, Gang!


For anyone else who might be following this, the reason that I ask is that the consequences are pretty significant. If we assume an exit image height at the Qualia's lens of about 1", then 310" of throw yields a 55" resulting image, or a "magnification" of 1:5.74 ((55-1)/310). If the rise is the actual pincushioning on a flat screen, then the screen edges would have to come forward 1.8 * 5.74, or 10.3", which would be a bit difficult to integrate into my living room!


Cheers!

MarkF
 

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The "rise" would be the front to back displacement of the screen surface at the center. IOW, the center would be that many inches inset from the l/r edges of the screen. Or the distance from the center of the chord to the center of the screen. This would be a 48'-3.5" radius.
 

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Hi MarkF:


I know that I am off topic in the sense that I am not being able to address your desire for a curved screen. I just completed my change to the CIH system with the same set up- Qualia, Isco 3 and a 2.35 flat screen. And I love it. There is hardly any noticeable pincushion, as Alan says. I was guided meticulously by Alan as I set it up.


Thease are my configurations:


Room size: 16ftW x 23ftL

Screen size: 58x136. It replaced my 65x116 HDTV screen.

Qualia lens: Mid Throw 1.4

Distance from Isco 3 lens to screen-16ft approx.

Seating- only one row 17 ft from the screen.

I do not see any loss of light after the Isco 3 was installed.


Just thought I would share this with you.
 

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Discussion Starter · #14 ·
Hi, Folks!


Dennis: Terrific! 3.6" isn't bad at all - the masking curtains themselves would have to be at least that thick against the wall, anyway. Excellent news, indeed! Based on that rise figure, it's also worth keeping in mind that the visual pincushioning with a plain flat screen should only be about 3.6/5.47 = ~2/3" at the top and bottom of the screen. Hmmm... I guess that long throw distances really do help with anamorphic lenses! Thank you again!


BillS2K: Very interesting - thank you for the information! It's encouraging to also know that I might be able to increase the screen size a bit more. Are you happy with the screen brightness in the IRIS2 position, or do you normally run it at IRIS1 or Open?


I'm also curious about what you use for HDTV. Do you retract the ISCO so that you can use all the screen pixels for HD content? I understand that ISCO offers a motorized version of this, but it costs almost as much as the lens itself! As always, I hate compromising, and I'd love to find a workable, esthetic way of fully utilizing the projector's resolution for both 2.35:1 and 16:9 content.


Have Fun!

MarkF
 

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Hi MarkF:


I know what you are talking about with regards to compromise. However, since I have a dedicated HT room I do not perceive any loss of light. I still have the Qualia on Iris 2 setting.


I know that the cost of the motorized version of the Isco 3 is the same, if not more than the lens itself. I have my Isco 3 permanently installed very close to the Qualia lens. Pursuant to Alan's advise I have decided to leave the lens there permanently.


With regards to HD material I have the option to continue watching it on 2.35 or switch to 16.9 with masking on the sides. My masking system is coming from Don at HTIQ. I hardly notice any loss of resolution but that is where the issue of "compromise" comes in.


My old HDTV screen was a DaLite High Power (1.8 gain) screen. Since I liked the PQ so much with the old screen I went ahead and ordered the same screen in the 2.35 configuration. I hope this helps.
 

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Discussion Starter · #16 ·
Hi, Bill!


Thanks again for sharing your configuration! I'm continuing to think about what I might do, and I may just have to wait until I can actually test the Qualia once it's here. The actual projected resolution for 16:9 use would be ~1452x1080 with a fixed lens, which is pretty close to the 1365x1024 that I'm already running.


Hmmm. A long time ago, I came pretty close to motorizing my hushbox (open/close), and even bought some gears, a stepper motor, and an RF remote control towards that end. In the process of building the hushbox itself, I found some heavy duty drawer slides that have essentially no slop, and they'd make a perfect mechanism for top-mounting the ISCO. A couple of limit switches, a motor controller, and a linear jackscrew motor should do the trick, along with that RF remote. Maybe I'll have to think some more about this.


One thing about this setup would be quite nice. With the lens shifted out of the optical path, I'd still have "perfect" image geometry for HDTV and HTPC, so I wouldn't need a curved screen - a bit of overscan only for 2.35:1 movies wouldn't bother me in the least. That would also make it possible to use a standard masking system like the HTIQ. By the way, what do you think of your HTIQ system?


Maybe I'll yet find a no-compromises solution...


Cheers!

MarkF


EDIT: This approach would also prevent the need for an HD scaler immediately, which would make this a lot more affordable. I may just have to get serious about this!
 
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