Panamorph increased horizontal picture? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 07-06-2019, 12:36 PM - Thread Starter
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Panamorph increased horizontal picture?

Hi I have the panamorph u480, I just wanted to ask if its normal that this lens increases horizontal picture length by 4,6% compared to a fixed frame screen of the same vertical height.

I measured the length of the projected picture on the wall with no screen. a store bought screen measures 250 x 106 centimeters and my projected picture theough the lens measures 261 x 106 cm.

Anyone here with the u480 that has experienced this too?
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post #2 of 8 Old 07-06-2019, 11:39 PM
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Originally Posted by Challe77 View Post
Hi I have the panamorph u480, I just wanted to ask if its normal that this lens increases horizontal picture length by 4,6% compared to a fixed frame screen of the same vertical height.

I measured the length of the projected picture on the wall with no screen. a store bought screen measures 250 x 106 centimeters and my projected picture theough the lens measures 261 x 106 cm.

Anyone here with the u480 that has experienced this too?
It should stretch it 33% as that is the designed performance, but there may be some range to it. I know my ISCO will over/under stretch depending on the focus(astigmatism).

Are you using a curved screen now? What was the aspect ratio of the source material? There are lots of reasons things don't line up. Your screen is 2.35:1 and your lens projects a minimum of 2.37:1 and the actual ratio of most scope films in the last 50 years is 2.39:1 or 2.40:1. Your measure of 2.46:1 seems off, though.
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post #3 of 8 Old 07-07-2019, 05:25 AM - Thread Starter
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Like I said I measured the projected picture on the wall because I think I will build a new flat screen, the movie used was Caprain marvel I think.

The projected image On the curved screen the length is not as long, I havent measured exactly but 10 cm shorter so more in the line with the correct width.

The curved scrren is ugly, I want a more streamlined look
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post #4 of 8 Old 07-07-2019, 05:27 AM - Thread Starter
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my last budget lens also was the same length on the wall, so I dont know if it has something to do with the projectors vertical stretch function??
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post #5 of 8 Old 07-08-2019, 03:34 AM - Thread Starter
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ok, I got an answer from panamorph, I am a little behind the minimum throw distance so that can cause the picture width to be slightly longer than normal. I guess that means that a circle projected is not 100% round, but the picture looks fine to me 🙂
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post #6 of 8 Old 07-08-2019, 09:51 AM
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Originally Posted by Challe77 View Post
ok, I got an answer from panamorph, I am a little behind the minimum throw distance so that can cause the picture width to be slightly longer than normal. I guess that means that a circle projected is not 100% round, but the picture looks fine to me 🙂
Not sure that the min throw would change width, usually changes distortion in form of pincushion and vignette. Also, the curved width should be narrower than the flat width as the edges come in toward the middle as you curve the screen and catch the light before it expands to the full width of the flat screen. Chord vs arc length.

Do you have another device that can do vertical stretch correctly for comparison?
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post #7 of 8 Old 07-08-2019, 11:09 PM - Thread Starter
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well that is the reply I got back, I think Shawn at panamorph should know. And like I said the picture projected at my curved screen is narrower, but I will switch to a flat frame and then it will be 10 cm longer, I dont have any more vertical stretching device.
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post #8 of 8 Old 07-22-2019, 04:21 PM
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Quote:
Originally Posted by ScottAvery View Post
It should stretch it 33% as that is the designed performance, but there may be some range to it. I know my ISCO will over/under stretch depending on the focus(astigmatism).



Are you using a curved screen now? What was the aspect ratio of the source material? There are lots of reasons things don't line up. Your screen is 2.35:1 and your lens projects a minimum of 2.37:1 and the actual ratio of most scope films in the last 50 years is 2.39:1 or 2.40:1. Your measure of 2.46:1 seems off, though.
It is called grid distortion and it gets worse, the shorter the throw. All anamorphic adapter that are HE have this issue. The difference cylindrical lens and the prisms is that correction can be ground into the cylindrical lenses. Prisms have flat faces so not much you can get for this short of curving the screen.

Project a grid, measure a square in the centre. The measure other squares along the same Horizontal line. You will notice the squares are not square, rather rectangles that are wider on x axis.

Sent from my CPH1701 using Tapatalk

Mark Techer

I love my Constant Image Height system!
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