# Larger Screen



## vinny0128 (May 7, 2010)

I have a Barco DP30 that will project a image 30 feet in height by 30 feet in width. Is it possible to make a anamorphic lens that will stretch the 30 feet in width to 60 feet. I'm trying to use the projector for a Drive-Inn movie screen that is 30 feet in height by 60 feet in width. Any help would be greatly appreciated.


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## Prof. (Oct 20, 2006)

Hi vinny and welcome to the Shack..

That's a commercial DLP Cinema projector and a bit different than your average home projector! :bigsmile:

Firstly, a prismatic lens is designed to stretch the image horizontally by 2.37 times the height..
To obtain a 60' wide image, you could only have an image height of approx.25'..
If you want to maintain the 30' height, then the screen would need to be 71' wide.!

Secondly, the projector would need to have the facility to electronically stretch the image vertically..
This is usually facilitated by using the LBX setting on a projector..
Failing that, the other alternative would be to use a scaling device..

And thirdly, I think the biggest problem might be the diam.of the lens used on that projector..
The biggest prisms available for an anamorphic lens are only 5" x7"..
If the lens on the projector is any more than 3" in diam.,then I think you will have a problem with vignetting..Even then it might be doubtful whether the prisms would be big enough..

From the look of the photo I saw, it looks like you would be able to get the A lens right up against the projector lens, which will help..if all the other parameters are suitable..


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## vinny0128 (May 7, 2010)

I did some measurements on the Barco DP30 Projector Lens. The lens is 3" in diameter. The lens is only 1/8" from the end of the lens housing. I actually could get the prisms about 3/16" from the lens. And also the projector does horizontal and vertical stretch. I just cant get it to stretch horizontal 60'. 40' is the biggest it will go. Is it still possible to use the prisms to get this picture size? What would the picture out of the projector have to be for size? Kind of new at this. I thank you very much for your help with that reply. Also, how would I build a anamorphic lens for this? Thanks, Vinny


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## Prof. (Oct 20, 2006)

With the projector having a vertical stretch facility, there shouldn't be any problem to get a scope image using an anamorphic lens..

If the screen is 30' high, then once the lens is set up and placed in front of the projector lens, you will have an image 71' wide!

To do this, you first of all set the AR on the projector to 16:9.and play a 16:9 DVD or Blu-ray..
Position the image so it centered on the screen, and extends to the full height of the screen..
This is best done by using min. zoom and moving the projector back (if that's possible) to fill the screen..

Then play a 2.35:1 movie and select LBX or whatever setting is available on the projector to give you vertical stretch..
That will then stretch the 2.35 image vertically to the full height of the screen..
Then when the AL is placed in front of the lens, the image will be stretched horizontally to fill the full width of the screen..

What I would suggest is that you just buy a couple of 5"x7" prisms, and sit them in front of the lens temporarily and adjust the angles to get the image to fill the full width of the screen..
If this should work OK and you don't get any image cut off, then you can make a case for them later..

To give you an idea of the angles required and how to set up the prisms, this article explains it clearly..
http://www.zuggsoft.com/theater/prism.htm


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## Prof. (Oct 20, 2006)

Hey Vinny..Did you ever get the anamorphic lens set up working with the Barco DLP projector?


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## Mark Techer (Jan 17, 2008)

You'd be wanting something better than a DIY prism pair on that projector.


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