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Discussion Starter · #1 ·
Has anyone compared these two? I perfer the verticle compression of the Panamorph over the horizontal expansion of the ISCO II for ease of setup reasons. For those with existing setups of a XGA projector on a 16:9 screen, it seems like the Panamorph would just fit right in with no keystoning or zooming issues. Of course the biggest advantage of the ISCO II is the likelihood of actually recieving one.


But are there differences in image quality, such as distortion, loss of light, etc.?
 

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Just a guess (I haven't seen a panamorph yet):


The panamorph seems to be some kind of "home-built" device with oil-filled prims. The oil-filled prisms are taken because of the price, the same idea had a guy here in germany who experiments with a home-built anamorphotic lens.


ISCO is a company which provides lenses to cinemas. The ISCO II is a highly professional and AVAILABLE anamorphic solution. They use high quality optical media and coating. Zou just have to see this lens in reality and you don't doubt that this is a good thing.


Compare the prices: 2.5K(now for a panamorph that doesn't seem to exist) vs 1K(ISCO powerbuy ACTUAL!!).


I know how I would decide.
 

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The whole reason the Panamorph project got started is because the vertical compression of the Isco, which affects throw ratio, is harder or impossible to apply with many projectors. The Panamorph was specifically designed as a horizontal compression lens so that it would not affect throw ratio.


Also, as I understand it, the horizonal prism approach might introduce less distortion than the vertical round lens approach.


The problem is that, aside from the Selecos and a few others, many projectors have relatively short throw ratios and the Isco would make that shorter still. That's why I can't use the Isco, otherwise I'd have one in a heartbeat.


Dan
 

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Dan,


There was a review of the Panamorph back in December of 2000 in which the Panamorph was compared to an ISCO II. If you search the forum archives it should show up.


One minor point aobut the differences between the lenses.


Panamorph compresses the image along the vertical axis. This has the effect of increasing the throw.


The ISCO I and ISCO II both expand the image along the horizontal axis, which tends to shorten the throw.


The deal with throw is that usually it's the vertical dimension of a room that controls the absolute screen height. Since the Panamoprh compresses in the vertical is allow the projector to be moved farther from the screen to achieve the same vertical size.
 

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Does whether or not the panamorph changes the throw depend on whether you are using a 16:9 or 4:3 screen? Seems if you are using a 16:9 screen it would compress the entire 4:3 panel into the same area that was previously being filled by only the middle portion of a 4:3 panel projector. If you are using a 4:3 screen you would have to move the pj back to fill the screen.
 

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If you are using a constant-height, variable-width setup (ie. 16x9 screen), then the ISCO seems ideal.


If you are using a constant width, variable height setup (ie. 4x3 screen) then the Panamorph seems ideal.


This of course is only when you want to remove/install the lens to switch between 16x9 and 4x3. If you want to electronically scale to get the 4x3, then it really doesnt matter.


Andy K.
 

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Joe,


The Panamorph compresses vertically and the throw ratio is based on throw distance to screen WIDTH.


Therefore, the Panamorph leaves the throw ratio UNCHANGED.


If you could project a full width letterboxed image from your projector onto a 16:9 screen without

a Panamorph - then you can add the Panamorph with NO physical change to the setup. [ Just rescale

the image to use more pixels.


You are correct - that since the ISCO expands the image horizontally - it decreases the throw.


So it is not that the ISCO decreases throw and the Panamorph increases throw - but rather ISCO decreases

throw while Panamorph leaves throw unchanged.


Greg
 

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Quote:
Originally posted by Morbius
Joe,


The Panamorph compresses vertically and the throw ratio is based on throw distance to screen WIDTH.


Therefore, the Panamorph leaves the throw ratio UNCHANGED.


If you could project a full width letterboxed image from your projector onto a 16:9 screen without

a Panamorph - then you can add the Panamorph with NO physical change to the setup. [ Just rescale

the image to use more pixels.


You are correct - that since the ISCO expands the image horizontally - it decreases the throw.


So it is not that the ISCO decreases throw and the Panamorph increases throw - but rather ISCO decreases

throw while Panamorph leaves throw unchanged.


Greg
If you base the throw ratio of the ISCO to screen HEIGHT, one could argue that the throw ratio remains unchanged too.


Consider this setup: You fit the picture of your 4:3 panels on to a 16:9 screen, while aligning the picture vertically top-to-bottom for 4:3 material and while zooming the picture to fill the entire screen for 16:9 material. In this setup you could add an ISCO II with NO physical change to the setup, very similar to what you said about the panamorph.


One lens enlarges the image (ISCO), hence decreasing the throw ratio. One lens compresses the image (panamorph), hence increasing the throw ratio.


The important thing is IMHO that whether or not a physical change to the setup is required entirely depends on what screen ratio is being used and on how much headroom for zooming is left to compensate the effect of the lens.


Cheers

Mike
 

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Mike,


You are making a symmetry argument - but the situation is NOT symmetric.


First, throw ratio is defined with respect to

width - not height. Of course, one could define

it based on height.


However, there is a substantiative difference.


If you do not have either lens and show a 16:9 movie as letterboxed - then you have setup the

projector so that it projects the proper width image. Assuming a 16:9 screen, the "dark" pixels

are targeted above and below the active area of the screen. With the addition of the Panamorph

and vertical compression - you don't have to change the setup. It's OK horizontally, and the

Panamorph merely redirects the previously unused pixels that were firing high and low onto the

active screen.


With the addition of an ISCO, and its horizontal expansion - if you did nothing else, you would have

an 16:9 image that was both too wide [ due to the ISCO's horizontal expansion ], and too tall -

because you already have the "dark" pixels overscanning the screen vertically anyway.


You must then zoom down this oversized image with either a zoom lens or repositioning the projector

so that the image properly fills the 16:9 screen.


Unlike the ISCO, the Panamorph does not require a change in zoom or projector position - which is

why it is so coveted.


The situation is NOT symmetric - because when you do not have a lens and project a letterboxed image

you are overscanning the 4:3 image vertically but not horizontally. That's why ISCO requires a change

in throw, but Panamorph doesn't.


Greg
 

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This is a great axplanation but it seems that the majority of people using a 4x3 projector also uses a 16.9 screen therefore letting the image speil on top and button of the screen so the panamorph would be a better option. To me I would go with ISCOII for being a German manufacture.
 

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Discussion Starter · #11 ·
Quote:
Originally posted by dynamike2000



If you base the throw ratio of the ISCO to screen HEIGHT, one could argue that the throw ratio remains unchanged too.


Consider this setup: You fit the picture of your 4:3 panels on to a 16:9 screen, while aligning the picture vertically top-to-bottom for 4:3 material and while zooming the picture to fill the entire screen for 16:9 material. In this setup you could add an ISCO II with NO physical change to the setup, very similar to what you said about the panamorph.


Cheers

Mike
The problem with that is the way projectors zoom. The top of the image stays at approximately the same position (assuming a ceiling mount setup). To get the 4:3 image to fit inside the 16:9 screen you need to tilt the projector and then you then get keystoning. Another problem is many projectors have only 1.3 zoom factor and you need at least 1.33 zoom to accomplish that if you set it up perfectly.
 

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Basically, it comes down to the following.


If you already have a projector that is setup to project a widescreen image on a 16:9 screen by using

only a portion of the 4:3 panel - then you know you can use a Panamorph. You just put the Pannie

in front of the PJ and rescale vertically.


If you have an existing setup, and want to add an ISCO - then you are limited by the need to alter

the zoom on the PJ. You may not have enough freedom in zoom - and may have to reposition the

projector - alter the throw - which may or may not be possible based on your current setup.


With an ISCO, your effective throw range is altered.


For example, if you have a JVC D-ILA, and a 10 foot wide screen, then the zoom on the JVC can handle

throw distances of 21 feet to 31 feet.


If you put a Panamorph in front of the JVC, the permitted throw distances are still in the range

from 21 feet to 31 feet.


If you put an ISCO in front of the JVC, then the range of throw distances becomes 15.75 feet to

23.25 feet.



Greg
 

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Quote:
Originally posted by Morbius
Mike,


You are making a symmetry argument - but the situation is NOT symmetric.


[...]


The situation is NOT symmetric - because when you do not have a lens and project a letterboxed image

you are overscanning the 4:3 image vertically but not horizontally. That's why ISCO requires a change

in throw, but Panamorph doesn't.


Greg
Greg,


from a practical point of view and for the scenario you described you are, of course, 100% correct. I also believe (not sure though) that the majority of HT enthusiasts mostly watch widescreen material. Thus the scenario applies for most people.


My point was (besides being devil's advocate ;)), that from a theoretical standpoint JoeFloyd is correct: A "stretching" lens decreases throw distance, while a "squeezing" lens increases it.


If you only look at the constant axis, of course, the throw distance remains unchanged with either lens. However, the constant axis may not *always* be the horizontal one.


Since both lenses use a different axis here (hence your non-symmetry argument, which I like a lot), we could probably discuss this until eternity. :)


Cheers

Mike
 

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Mike,


Joe's argument that ISCO decreases and Panamorph increases throw doesn't hold in either the constant

height or constant width cases. There are 2 cases:


Constant Width: ISCO decreases throw, Panamorph throw is unchanged.


Constant Height: Panamorph increases throw, ISCO throw is unchanged.


One or the other lens will leave the throw UNCHANGED depending on which case.


Additionally, the two cases are not of equal weight - the constant width is preferred - because

of what you do if you setup the PJ without a lens, and add the anamorphic lens later - that's where you

"break the symmetry".


It's natural for a physicist to make such an argument.


Dr. Gregory Greenman

Physicist
 

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Two sides of the same coin really. Depending on your masking system, current screen aspect ratio, projector mounting, zoom settings, etc... either lens may work better in a given situation. However, if the projector is already mounted the Panamorph will tend to be the easier to install.


If like many you start with a 4:3 screen and then try an anamorphic lens, you find that the 16:9 aspect ratio of the image has freed up some real estate along the vertical dimension of your mounting location. This is usually because rooms are rectangles and not squares. At which point, you may think to convert your screen to 16:9. Converting to 16:9 will almost certainly result in a wider screen than your 4:3. At which point if you're using the Panamoprh you would want to zoom your projector or mount it farther back.


Then main difference with the ISCO is that if you start with a 4:3 screen you have to either remount the projector closer to the screen or zoom it in to start. Zoom setting do affect the contrast, brightness and image uniformity. Generally speaking, a neutral zoom setting is the preferred setting.


The result is the same, but how you get there is a little different.


There are a lot of possibilities here, and the end user is left to ponder the approach that will work best in their particular situation.
 

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Just trying to follow along here...


So if you start with a 2.35:1 screen and have mattes that will convert the screen to 16:9 and 4:3 with a constant height and using a 16:9 fixed position projector the ISCO would be the best option? Am I close?
 

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Joe,


Yes - if you are talking about a new installation - and one hasn't chosen a lens or a projector...

then you have freed up some additional degrees of freedom. Without the constraint of having a PJ

with a given zoom range - then you could chose an alternate projector, or alternate mounting to make

either lens work.


What is a "neutral zoom"? For any given setting of the zoom lens, I can achieve the same effective

zoom by introducing an additional optic and adjusting the zoomable lens. So what is special

about any given zoom factor that makes it "neutral"?


Greg
 

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I believe that you have fleshed out the differences with regard to the expansion/compression issue fairly well, but the big difference is the need for the panamorph lens light entry to be mounted several inches (3-4"min)below the projectors lens in a ceiling installation. This is required so that you can manipulate the rotation of the lens about the x-axis. Without this ability it is very difficult to dial in the image and maintain the proper AR. Since there was little distance between the bottom of my hushbox and the bottom of the projector, this was impossible without construction modifications to the box (drop the box or construct a new one).


With a D-ILA projector if you mount your projector at approximately 1.9 screen widths you can use either lens.

Just watch the vertical height issue.
 

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Are you guys going to make me Krazy?:confused:


I have a panamorph here and I know exactly what happen when I put it in front of my projector. Now is there someone with an Isco II an with a 16:screen that can tell me what happen when he is looking a projected picture 3:4 on that screen and put an Isco lens in front of the projector, without changing anything else?:rolleyes:


Federico
 

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Wow, so much geometrical talk regarding the difference between them........Ok, guys, all you lucky Panny owners, what are the Image difference? Enough about the 4:3 stretch/compress/throw distance etc., etc., all which has been covered many time and can be reviewed by doing a search........what about the actual image fidelity difference??


Damn, I wish I had my Panny as I also have an ISCO-1 and would be reporting my subjective views. So, lets hear the image fidelity comparisons.


thanx, Jaime
 
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