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Quote:
Originally Posted by TRI-MONITOR /forum/post/0


According to widescreen museum it is 2.35:1.

Yet true CinemaScope is supposed to be 2.39:1...


For standard "video" Scope projection, the AR is actually 2.37:1 (1.78 x 1.33 = 2.3674 or 2.37 when rounded), but member Vern Dias believes that the screen should be wider (his screen is 2.66:1) to allow CIH playback of all ARs...


Mark
 

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Lens will get it to 2.37 anything over would need to be zoomed or scanned to get to fit.


Nate
 

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Discussion Starter · #5 ·
If you look at WSR they actually measure the AR of scope films presented on disc, many exceed 2.35:1. My understanding is that Stewart makes their masking systems and screens at 2.40:1.


This would seem to take into consideration the fact that so many films end up wider and would have black bars top and bottom (albeit small ones) otherwise.


Art
 

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I was planning on 2.40 figuring on having curtains to mask the sides. I like the simplicity of 5'X12'. Other than that I know squat....except what I read here.
 

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If you do the math, you get a bot of rude shock here.


The anamorphic lenses stretch for video apps is based on 33%.


Therefore the amount of vertical stretch has to be 33% to or the lenses would over stretch the image.


Yet the black bars of most CinemaScope films occupy about 25%. 33 - 25 = 8 / 2 = 4% top and bottom variance that you won't see when using the full 1.78:1 panel and an anamorphic lens in CIH.


If my math is right (based on the above) I should not see any letter boxing on my screen until the image AR reached 2.55:1.


At this stage, I am also not using an external scaler, but relying on the 16:9 enhanced function of the source (being DVD) and the 4 x 3 zoom of the projector. The prisms in the lens are set based on the 2.37:1 AR of the screen found simply by 1.78 x 1.33 = 2.3674 (rounded is 2.37).


There are ways around this, but then you end up not using the full panel width to do so, I guess you need to work out what is more important, Full Panel Use or Original Aspect Ratio...


Mark
 

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Quote:
but member Vern Dias believes that the screen should be wider (his screen is 2.66:1) to allow CIH playback of all ARs...

But, remember that my anamorphic lens provides a 1.5X expansion, not the normal 1.33X expansion. 1.77:1 x 1.5 = 2.655:1. This means I rarely use the full 1920 horizontal pixels, even for 2.40:1. However, it also means that I can display films like "Mutiny On The Bounty, "Ben Hur", and "Battle of the Bulge" with no letterbox bars visible at very close to the full negative AR of the MGM Camera 65 / Ultra Panavision frame.


In addition, I can also display the early CinemaScope films at their full 2.55:1 AR without visible letterbox bars.


Vern
 

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Quote:
Originally Posted by Vern Dias /forum/post/0


But, remember that my anamorphic lens provides a 1.5X expansion, not the normal 1.33X expansion.

So Vern, do you have to apply some horizontal squeeze as well as vertical stretch to get the desired electrical compression before optical expansion?


The description (and some photos I've seen) make your system the ultimate in CIH...


Mark
 

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Quote:
you have to apply some horizontal squeeze as well as vertical stretch to get the desired electrical compression before optical expansion?

Yes. My primary feeds are from an HTPC using Theatertek for SD and PowerDVD with YXY AR control for HD. I also use a CII scaler for FIOS. The anamorphic lens is an ISCO Cinema DLP. Almost 1.5x the size and weight of an ISCO III.


Vern
 

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Quote:
Originally Posted by Art Sonneborn /forum/post/0


I'm trying to get some ducks in a row for my theater. I'm wondering, since the actual measured AR of scope films is often 2.40:1 and not 2.35:1 is that the screen ratio that is best also ?


Art

After debating this topic and finally going with and using a 2.37 screen, I don't think it really matters whether your screen is 2.35 or 2.40 or something in between. I just simply adjust the stretch of my Prismasonic lens so I get a little overscan onto my black velvet screen borders. Then I call it good, and enjoy the movie. I'm sure I often don't have the EXACT right original AR of the movie presented on my screen, but the difference is so slight that I can't tell.
 

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The only point to consider with adjustable prisms (and you might note that Prismasonic's website now lists "Scope" screens as 2.37:1, not 2.35:1 - who would have thought that 0.02 would make such a difference) is getting the correct amount of stretch so that a circle is actually round. The globe on the MCA Universal leads is a good example to use to base whether or not you have true geometry...


Mark
 

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Quote:
Originally Posted by CAVX /forum/post/0


The only point to consider with adjustable prisms (and you might note that Prismasonic's website now lists "Scope" screens as 2.37:1, not 2.35:1 - who would have thought that 0.02 would make such a difference) is getting the correct amount of stretch so that a circle is actually round. The globe on the MCA Universal leads is a good example to use to base whether or not you have true geometry...


Mark

Mark,


Yes, I went with a 2.37 screen because that's what my Prismasonic lens does, and I believe 2.37 seems to be a good compromise between 2.35 and 2.40.


As far as the correct geometry, I think you are missing my point. While I am a big believer in OAR, and making reasonable attempts to get correct geometry, stretching a 2.35 movie to 2.37 doesn't bother me at all. On my 126" diagonal screen you are only talking about one inch difference in screen width when you do this. While the circles might not be perfectly round, it is very difficult to see.


BTW, Mark, I've never had a chance to thank you and others here at the CIH forum for the help in getting my CIH setup going. Your website is very good and helpful. FYI, I am using a Prismasonic H-1400FE lens, Pansonic 900 projector, and a DIY accoustically transparent 2.37 screen using the SeymourAV (Phifer 4500) screen material. This is a sweet setup, and my total cost of the fore mentioned equipment was right at $3,000. My family sure likes it, and the only problem is it makes my 64" HDTV seem small!
 

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Put my screen together Saturday, and I had ordered it with a 2.37:1 ratio. After putting it up I centered the projector on it then played 1.85 and 2.35 material.


With the picture zoomed so the top and bottom were as close as I could get it to the top and bottom borders of the screen without showing any voids, the picture width for wide 2.35 put the borders width wise just about perfectly aligned with the left and right borders of the screen, maybe a hair wider than the screen. A perfect fit. This was with several movies, including Tombstone (recorded off HDnet I think), and Lord of War from last night. I put in Battle of the bulge, and it fit width wise, but had small black bars top and bottom due to it's extra width.


All in all I would recommend the 2.37 aspect ratio for the screen, seems to be perfect for me.


Allen
 

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Quote:
Originally Posted by mlbrand /forum/post/0


BTW, Mark, I've never had a chance to thank you and others here at the CIH forum for the help in getting my CIH setup going. Your website is very good and helpful. FYI, I am using a Prismasonic H-1400FE lens, Pansonic 900 projector, and a DIY accoustically transparent 2.37 screen using the SeymourAV (Phifer 4500) screen material. This is a sweet setup, and my total cost of the fore mentioned equipment was right at $3,000. My family sure likes it, and the only problem is it makes my 64" HDTV seem small!

Thank you for your comments and I'm glad this is working for you. Have you sent Alan any pictures yet?


Mark
 

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Quote:
Originally Posted by Allen /forum/post/0


Put my screen together Saturday, and I had ordered it with a 2.37:1 ratio. After putting it up I centered the projector on it then played 1.85 and 2.35 material.


With the picture zoomed so the top and bottom were as close as I could get it to the top and bottom borders of the screen without showing any voids, the picture width for wide 2.35 put the borders width wise just about perfectly aligned with the left and right borders of the screen, maybe a hair wider than the screen. A perfect fit. This was with several movies, including Tombstone (recorded off HDnet I think), and Lord of War from last night. I put in Battle of the bulge, and it fit width wise, but had small black bars top and bottom due to it's extra width.


All in all I would recommend the 2.37 aspect ratio for the screen, seems to be perfect for me.


Allen

I agonized over this for weeks and finally pulled the trigger last Friday, ordering a 2.35:1 screen, having got advice that with a bit of overscan, it wouldn't matter.
 

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I think you will be happy with that, with my screen the difference between 2.35 and 2.37 is only 1 inch, or less than 1%.


Allen
 

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Quote:
Originally Posted by CAVX /forum/post/0


Thank you for your comments and I'm glad this is working for you. Have you sent Alan any pictures yet?


Mark

No I haven't posted any pictures yet, and I should. What's the best way to post pics on this forum? I've never done that here before.


Mike
 

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Art -


IMHO, the best approach to designing and implementing any screen which you want to be able to handle multiple CH AR's is to do what many (most?) commercial theaters do. Put up a screen that is larger than you know you'll ever need, then use your masks to frame that material as you need to.


If you do that, it won't matter whether you're dealing with 2.35, 2.37, 2.40 ... whatever.


My actual reflective screen area is about 100" X 36". When I put that in place, I knew I'd never use more than about 33" of height and that I'd probably go out to about 86" max width. In fact now, I never go out beyond 85" for Camera 65 ... and when I do, I drop the top mask down about an inch and a half.


Any decent screen design will allow you to adjust your stops for the left/right masks so you can handle all these contingencies.


And Mark - Yes, the black bars in consumer letterboxed scope content do represent about 25% of the screen area. And so a 33% HE lens does the trick. That's because 25% is 33% of the other 75%. Many people find that difficult to understand ... but the fact is that when 25% of your 1.78 screen is black bars and the other 75% is the scope image, then a 33% HE lens is exactly what you need to take you out to about 2.37.
 
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