Why do i need a Panamorph lens? - AVS Forum
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post #1 of 3 Old 05-31-2001, 01:39 PM - Thread Starter
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If I were to buy a JVC G15, run it with a HTPC with Diluard, YXY and all other needed software, is a Panamorph lens still needed. I understand the difference between 1.78:1 and 2.35:1. Could the picture be manipulated using any of the above programs? Which format ie. 1.78 or 2.35:1 is the most popular format for dvd's. Is there a new DILA projector that is coming out that would not need a lens and could always display in the correct ratio without black bars. I made mattes for my RPTV to block out the black bars. What a difference. Is this what the Panamorph does -get rid of the black bars? Which Panamorph lens is more important - the one for 1.78 or the new Panamorph II for 2.35:1. If it's that important, I want to get in the the low pre-release price.

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post #2 of 3 Old 05-31-2001, 11:44 PM
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The overall resolution of the display is always a constant. How the information in the video image is mapped onto the display is a variable. The different lenses that you are considering change the aspect ratio of the display, but not the resolution. Basically, the aspect ratio is changed by changing the shape of the individual pixels, and how the image is mapped on the physical display if modified to account for the lens. This sounds more complicated than it really is, but it does take some effort to understand the difference between source aspect ratio and display aspect ratio.

There are some really informative threads that go into great detail about the positive and negative aspect of each lens. The current ISCO vs. Panamorph thread is one such thread.

When it come to aspect ratio there are basically a couple things to keep in mind. 16:9 is the aspect ratio of HDTV, it you plan on watching lots of HDTV with a 4:3 projector, it makes sense to get the Panamorph I or the ISCO II. If you watch alot of DVD movies, its a more difficult situation.

The aspect ratio of movies can vary all over the place. Action and big budget movies tend to go for the wider 2.35 aspect ratio, while smaller or more plot driven movies tend to favor 1.78. There is no hard and fast rule here, but that's something I've noticed. So, either the ISCO II, Panamorph I or the Panamorph II could be useful for DVD. Your prefrence for movie style may make the decision for you.

It's also worth noting the the Panamoroh I and ISCO II can be used with upcoming 16:9 projectors to produce a 2.35 aspect ratio. There is some question as to how the internal scalers of the newer 16:9 projectors will operate. If they duplicate the behavior of the Sony 10HT, that will make them less useful with an anamorphic lens. But, if the internal scaler can be bypassed for computer based inputs, these new projectors can be easily used with the Panamorph I.

The choice between ISCO and Panamorph is one between constant height or constant width. The ISCO lens is a constant height lens and is similar to how commercial theaters change aspect ratio. The Panamorph is a constant width system and is similar to how TV letter boxing is done. You'll have to read the other threads to get a full understanding of what that difference means in practical terms and how it will affect the set up in your particular home theater.

The major difference is that the ISCO shortens the throw needed to achieve a given screen width, while the Panamorph leaves the throw unchanged. This is of course a width base view of the world. If the height is to be held constant then the ISCO does not affect the throw while the Panamorph will lengthen it. For most home theaters using a wide aspect ratio screen, the width is the limiting factor to the theater design and that's the reason the ISCO is often said to shorten the throw.

[This message has been edited by JoeFloyd (edited 06-01-2001).]
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post #3 of 3 Old 06-01-2001, 01:37 PM
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Ken,

Joe just gave a very comprehensive discussion on the
use of the anamorphic lenses. I would just add, that
although you can use an HTPC to map a widescreen format
onto the G15's native 4:3 aspect ratio - you do that by
turning off some of the G15's pixels - those that would
correspond to the black bars above and below the picture
as seen on a 4:3 direct view set.

If you have an anamorphic lens, the HTPC can stretch the
image to fill the 4:3 D-ILA panel. Therefore, the full
light output of the projector is available - no "off"
pixels. The lens then restores the image to its proper
aspect ratio.

The Panamorph does get rid of the black bars in the sense
that the projector is not "projecting black" All of the
pixels are mapped to the active image by the Panamorph with
16:9 material. If the material is 2.35, then there are
black bars with the Panamorph I - although less than if
you mapped a 2.35 onto a 4:3 panel without a Pannie.

Note that the Panamorph I can map a native 16:9 panel,
like that in a 10HT to 2.35 directly.

The ability to dispense with the black bars for 2.35
aspect ratio material for projectors with native 4:3
aspect ratio is what the Panamorph II is all about.

Greg

Dr. Gregory Greenman
Physicist
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