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Discussion Starter · #1 ·
Does anyone have any pictures of a FIXED ISCO III anamorphic lens set-up? All I ever see are with one of the slides. I'd also like to hear from these folks how they deal with 16:9 material and what projector they are using it with.


Thanks!
 

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Vern Dias does... He's the guy to chat with..
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by Vern Dias /forum/post/15468363


Isco Cinema DLP lens (1.5X) http://mysite.verizon.net/tvdias/LensMount.jpg


HTPC -> Theatertek for DVD Arcsoft TMT = YXY for BD & HD DVD

Using 10 preset AR's


Qualia 004 Projector http://mysite.verizon.net/tvdias/Qualia01.jpg


5' X 13'6" curved screen.


Vern

Hi Vern,


Thank you for the picture, and the info. I'm trying to determine if a fixed ISCO III is viable for a 720p 3-chip DLP and the aspect ratio control it offers. Any advice there?
 

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Quote:
Originally Posted by Scott Wallace /forum/post/15468493


Hi Vern,


Thank you for the picture, and the info. I'm trying to determine if a fixed ISCO III is viable for a 720p 3-chip DLP and the aspect ratio control it offers. Any advice there?

It can work quite well, but the reason Vern suggests using a scaler or HTPC is for all the "odd ball" ARs that came out before the SMPTE settled on 2.39:1 for CinemaScope. The differences can be small like the difference between 1.85:1 and HDTV's 16:9 which is just 4%, but in a true CIH system, the 1.85:1 image will be wider than the 1.78:1 image. Scaling with the projector will require you to apply a small amount of zoom to the image to make this happen. It is not a huge ask, but can be a bit of a PITA if done on a regular basis. The presets allow this to be a one button step and no zoom required.


The ISCO is also 1.33x so you will be limited to 2.37:1 where Vern has the option to go wider because of his 1.5x lens. The difference is that Vern only uses his full panel width for "classic" films as no modern cinema films are wider than 2.40:1. This is in no way a problem as the image will always use the full vertical rez of the projector.


I have gone back to leaving the lens in place all the time because it makes set up and AR changing much more user friendly...


Mark
 

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Obsessives who strive for perfection down to the last 1/2", please don't read, as you will go mad...

Little-realised problem with fixed systems:

Because all anamorphics stretch less in the center than at the edges (it's optics: even though the final edge-to-edge ratio with true 'scope material may be 1.33x), a fixed system projecting exact == 4:3 with the aim of resulting in exact == 16:9 will probably not quite make it, more like 15.5:9 (unless you can tweak your scaler to deliver a slightly wider "4:3" picture, something like 4.4:3).


Just sayin'.
 

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I was using an ISCO II with my last (720 Optoma H78) pj and that was a fixed system:






Like Vern I was using HTPC.


I did have a Prismasonic H1000 lens with pass through mode, but found I was using pass through less and less, so when I upgraded to the ISCO I had no intention of moving it out of the light path.


Gary
 

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I have a fixed ISCO III setup with a Panny AE-2000 and a Stewart ST130 fixed 2.35:1 screen with a wide border. I'm on my third projector with the same lens and screen and have been happy with the results.
 

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Is everyone's ISCO perpendicular to the primary on their projector? I have to tilt my ISCO III down to get a proper image. The only issue is that unless I defocus slightly, I get an artifact that I think is called chroma aberration??? I have searched the threads anyway and I think that is what I am experiencing. It is not noticeable unless there is a bright image on the screen like sky or snow. Not a dealkiller for me but I would like to NOT have the issue. I also have optical glass because I have a separate projection booth. So the light passes through the primary, then the ISCO III and then the optical glass.
 

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Mine had a slight tilt to follow the beam angle, though it's hard to tell from the image.


What does the artifact look like exactly?


Gary
 

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It's really hard to describe. I guess I should take a picture of it. It is rounded lines. I suspect that anyone with an ISCO could reproduce the artifact by putting on a white screen and changing the focus on your projector. If my projector is in perfect focus, I can make the artifact disappear by defocusing. I will snap a pic in the next couple days and post it here.
 

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Please do as I don't think anyone else has reported this problem before...


Mark
 

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Discussion Starter · #13 ·

Quote:
Originally Posted by CAVX /forum/post/15501378


Please do as I don't think anyone else has reported this problem before...


Mark

I guess my main question is, how do you view 16:9 material in a 16:9 aspect ratio on a 2:35 screen with a fixed ISCO? Or do you?
 

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Quote:
I get an artifact that I think is called chroma aberration???

Chromatic abberation is basically color fringing at the borders of objects in the image.


CA is common in some projectors and any HE anamorphic lens will make it more apparent in the horizontal direction.


I assume you have adjusted the Isco's astigmatism adjustment properly.


Vern
 

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Quote:
Originally Posted by Scott Wallace /forum/post/15502032


I guess my main question is, how do you view 16:9 material in a 16:9 aspect ratio on a 2:35 screen with a fixed ISCO? Or do you?

Scaling pending, you can preset your scaler/HTPC or use the 4 x 3 mode of your projector. Basically, a HDTV image is squeezed from 1.78:1 back to 1.33:1 (which will now look tall and thin with the lens removed) will be optically expanded by the lens to produce a geometry correct 1.78:1 image...


Mark
 

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Quote:
Originally Posted by Vern Dias /forum/post/15502064


Chromatic abberation is basically color fringing at the borders of objects in the image.


CA is common in some projectors and any HE anamorphic lens will make it more apparent in the horizontal direction.


I assume you have adjusted the Isco's astigmatism adjustment properly.


Vern


Thanks Vern. If that't the definition then what I am seeing is NOT chroma abberation. I have adjusted the astigmatism to death! I really believe that I need to spend some more time with the lens adjustments. For example, and I know this thread is for FIXED setups, but when I move the lens out of place for 16:9 material, the image is not perfectly centered on the screen. It is not off center by a lot but it off nevertheless. I have been living with my adjustments and the defocussed image because of the challenge of adjusting my lens. My projector and lens is in a booth and I only have a porthole for the light path. I didn't think to install a second porthole to allow me to see the screen!! That is probably what I really need to do but the thought of cutting in another hole isn't very appealing. Sorry for being longwinded. I will post pics of my setup and the artifact tomorrow or Saturday.
 

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Ouch on no second porthole!


It is best to get the image precisely centered, positioned, and focused without the anamorphic lens. Then add the anamorphic lens and position it so that the centering is correct. Then, adjust the astigmatism. If you need help adjusting the astigmatism, what you are looking for is that both vertical and horizontal lines focus at the same time. Use a crosshatch pattern with single pixel wide lines. To check the asigmatism, "rock" the projectors focus back and forth and verify that both vertical and horizontal lines focus perfectly at the same time.


Vern
 

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Yeah, I redid EVERYTHING today, getting the 16:9 image perfectly centered first, perfectly focused, then activating the lens slide and redoing the adjustments for that. I am able to aget perfect focus, or at least REALLY close to perfect but I have those annoying optical anomalies. I have to slightly defocus to make them go away. In addition to focus, shifting the lens and zooming also changes the artifact. I am determined to get a good picture of the screen tomorrow with a 100% white field so everyone can see what I am talking about. Since I haven't run across any mention of this in other threads, I am assuming that people don't have this issue. I don't know if it is that my projector is not perfectly perpendicular to the screen, although I think it is, or if it has something to do with my long throw of 32 feet or the 16 foot wide scope screen size. Thanks for the advice and I will be reporting back to you. I think I will start a new thread so that I can stop hijacking this one.


My sincere appologies to the original poster
 

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16' wide screen? What PJ are you using? Microperf? Gain?


Thanks!
 

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Quote:
Originally Posted by thebland /forum/post/15515578


16' wide screen? What PJ are you using? Microperf? Gain?


Thanks!

The projector is a DPI HD-250 3 Chip

The screen is a Harkness Hall miniperferated with a gain of 1.5


Thanks
 
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