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Discussion Starter · #1 ·
Does anyone know of a lens that will stretch 4:3 to 2.35:1? I guess the old Superpanatar will do it but I also guess that it won't work for smaller home cinema screens. I saw that Schneider optics also made one for cinema use. Any input on this?
 

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Any of the fixed theatrical lenses will stretch a 4:3 image to 2.66:1, not 2.35:1.


That's because the actual AR of a scope image on the print is 1.2:1, not 1.33:1.


Vern
 

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Under what conditions in the home would you ever want to stretch 4:3 to 2.35:1?
 

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Quote:
Under what conditions in the home would you ever want to stretch 4:3 to 2.35:1?
Maybe he has a 4x3 projector and wanted to go to 2.35.
 

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Discussion Starter · #5 ·
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Originally Posted by Josh Z
Under what conditions in the home would you ever want to stretch 4:3 to 2.35:1?
Hm. I'm building a dedicated home theater room and was thinking of using the Canon sx50 for the picture. Since it is 4:3 and most movies are 2.35:1 i would use the whole panel of that projector. As simple as that.


If I were to use for exaple a Prismasonic lens (H-600), which they say does a stretch 1.5x, I could do 18:9 ratio. Is it possible to modify the prisms or are they too small? The stretch needs to be 1.75x.
 

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Danny the Who is absolutely correct. I have read through many threads on the same topic and all agrred that it was impossible to achieve and therefore, I went with the Isco 3.
 

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Quote:
Originally Posted by Anders Carlsson
Hm. I'm building a dedicated home theater room and was thinking of using the Canon sx50 for the picture. Since it is 4:3 and most movies are 2.35:1 i would use the whole panel of that projector. As simple as that.
I see. I assume then that you're also using a scaler that can stretch the movie image to fill the 4:3 pixel panel?
 

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You can achieve a "Scope" setup with a 35mm 2x projection lens and a 4:3 projector... as long as the Scope lens is big enough or short enough in length as to not produce any objectionable vignetting. I get good results stetching 4:3 to Scope proportions (or thereabouts) by using a French made 35mm Hypergonar H. Chretien HI-FI-2 lens ... two of which I acquired on Ebay several years back.


After taking the lens apart on one and adjusting the elements in a little closer by cutting the internal aluminum barrel (that houses the front element) shorter with a hacksaw!... but not cut too short as to cause the elements to sit too closely together and lose focus (that's important!)... I've also removed the plastic zoom and focus rings on the X1, to bring the Anamorphic closer to the projector's actual lens... add to that the distance to the screen (about 10 ft)... I'm assuming my horizontal squeeze is more like 1.9x.


I send the upconverted 1080i Scope image from my Zenith 318 player to my X1 vertically stretched to 1.78:1 (using the Zenith's handy vertical zoom, I push the black letterboxing beyond the top and bottom of the image). The X1 is set to 4:3 mode, so it further squeezes the Zenith's 1.78:1 image into that... the Zenith has some pixel cropping on the left and right, so the X1 is really displaying about a 1.30:1 anamorphic image. I also have adjusted the tracking option in the X1's menu to "0", so there's a further horizontal squeeze from the right at work, though very tiny. It gets me to about a 1.29:1 anamorphic image.


When all is said and done, I figure I'm getting somewhere between 2.44:1 - 2.47:1 on most modern scope movies, so that's what... 3% to 7% more horizontal stretch than I need, depending on the movie? You can't really see any difference... it looks correct enough to my eyes and pretty good with my 2.35:1 masking. Usually there's about 2.5 to 3 inches more picture area on the left and right on my curtains.

http://home.earthlink.net/~particlew...ector-lens.jpg


You can view some screenshots here ... and here (a bit higher res).
 

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Discussion Starter · #10 ·
Quote:
Originally Posted by Josh Z
I see. I assume then that you're also using a scaler that can stretch the movie image to fill the 4:3 pixel panel?
I'll be using HTPC only.


Nice work with the lens there Maxwell. Have you noticed any flaws with this setup. Any loss in resolution or CA?
 

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Anders,


I'm contemplating the same setup.


If you're using a scaler, you can use a 2:1 like Vern is talking about to get to 2.66 and then squeeze horizontally with the scaler to bring it to 2.35.


You'd have very slight black bars on the sides, but they would be off your screen.


A lot fewer unused pixels than showing 2.35 within 1.78.


Kind of a hassle to have two adapters for 1.78 and 2.35.


BTW, I have a Super Panatar and it is totally unsuitable. It's only good enough to whet your appetite for a continuously variable stretch lens :)



Ken
 

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Quote:
Originally Posted by Anders Carlsson
Nice work with the lens there Maxwell. Have you noticed any flaws with this setup. Any loss in resolution or CA?
Thanks. There is a slight loss in resolution and very minor (virtually invisible at 10 feet back) chromatic abberation. But the slight loss in resolution due to some inactive columns of micromirrors (775 X 600) is a pittance compared to sacrificing 45% of the micromirrors without the Anamorphic. There is some slight softening of the image that the Anamorphic adds, but it's actually pleasing and diminishes the screen-door effect.


I cooked up two images in Photoshop to illustrate almost exactly what I'm seeing at home. These are recreations only, not real photos (though pretty darn accurate). The first shows the active micromirrors that my X1 displays, the second demonstrates the exact pincushion effect and stretched pixels that my anamorphic lens imparts, as well as my 2.35:1 screen area:

Without Scope Lens (755 KB)
With Scope Lens (1433 KB)
 

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Quote:
Originally Posted by Maxwell Everett
You can achieve a "Scope" setup with a 35mm 2x projection lens and a 4:3 projector... as long as the Scope lens is big enough or short enough in length as to not produce any objectionable vignetting. I get good results stetching 4:3 to Scope proportions (or thereabouts) by using a French made 35mm Hypergonar H. Chretien HI-FI-2 lens ... two of which I acquired on Ebay several years back.


After taking the lens apart on one and adjusting the elements in a little closer by cutting the internal aluminum barrel (that houses the front element) shorter with a hacksaw!... but not cut too short as to cause the elements to sit too closely together and lose focus (that's important!)... I've also removed the plastic zoom and focus rings on the X1, to bring the Anamorphic closer to the projector's actual lens... add to that the distance to the screen (about 10 ft)... I'm assuming my horizontal squeeze is more like 1.9x.


I send the upconverted 1080i Scope image from my Zenith 318 player to my X1 vertically stretched to 1.78:1 (using the Zenith's handy vertical zoom, I push the black letterboxing beyond the top and bottom of the image). The X1 is set to 4:3 mode, so it further squeezes the Zenith's 1.78:1 image into that... the Zenith has some pixel cropping on the left and right, so the X1 is really displaying about a 1.30:1 anamorphic image. I also have adjusted the tracking option in the X1's menu to "0", so there's a further horizontal squeeze from the right at work, though very tiny. It gets me to about a 1.29:1 anamorphic image.


When all is said and done, I figure I'm getting somewhere between 2.44:1 - 2.47:1 on most modern scope movies, so that's what... 3% to 7% more horizontal stretch than I need, depending on the movie? You can't really see any difference... it looks correct enough to my eyes and pretty good with my 2.35:1 masking. Usually there's about 2.5 to 3 inches more picture area on the left and right on my curtains.

http://home.earthlink.net/~particlew...ector-lens.jpg


You can view some screenshots here ... and here (a bit higher res).
Amazing! But I definitely don't have the technical capability to take apart lenses! But I do want something that stretches 4:3 to 2.35:1. Anybody knows of a real, commercially available solution please post.


D
 

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Discussion Starter · #14 ·
So i take it there is no simple solution to this. The Hypergonar way works. I saw one at E-bay two days ago. I googled around and found this:


To few posts!!
 

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Anders


I had a serious look at this just a couple of months ago. Eventually I spoke to the guys at Isco in Germany (one of the 3 generally accepted makers of HT anamorphic lenses - Isco, Panamorph and Prismasonic).


They told me that the relatively short throw of most HT projectors is the problem. In a movie theater you have generally a 100 feet plus throw, in a HT maybe 15 to 20. That, I'm told, is the problem with lenses.


Now I'm no expert on lens design - if anybody knows diffrtrnt please post!


D
 

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Isco knows this subject inside and out. A short throw in a movie theater is maybe 60 or 70 feet. Thats why you would have to resort to what Maxwell did with his lens and I have done with the B&L anamophics on my 35mm projectors. Shortening the barrel is required to get the astimatism correctly adjusted at the relatively short 20 to 25 foot throw.


Vern
 

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I use a 1.75x MAGNARAMA anamorphic made in the U.K. and was primarily designed for super 8 filming and projection. It actually gives you around 2.33 :1 from a 1.33:1 frame.

By using THEATERTEK and a HTPC, I ''vertically stretch'' a 2.35:1 DVD within the 1.33 :1 frame until a circle appears round with the anamorphic in place. I still end up with some thin black bars top and bottom, but they are not detrimental to the image as far as I can tell.

The extra useage of panel area on my DLP projector with the anamorphic results in a very ''FILM LIKE'' image.
 

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Hey ziggyr


Would you mind sending me an email re lens and set up proceedure. I am located in Perth West Australia as well. Feel left alone here.

[email protected]

or

Tradewinds Hotel

9339 8188


Thanks
 
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