Constant Height Screen Explained - And a free Excel calculation Sheet!

[WriteSimply]

After having seen a constant height screen myself on a very high end system (close to US$29k for the screen, the projector, the anamorphic lens), I am convinced that it is the best home theater option. Thanks to Deci, he (she?) convinced me that I could avoid all of the mess with anamorphic lens by zooming in the video to fill in the 2.39 screen.

I just can't figure out how to make the zooming in work with most 1080p projectors out there. Like does the zoom has a numbered zoom) as in like from 0 to 100) or is it all trial by error? An auto function would be best.

Anyways, here is a simulated 100" image from a 1080p projector/HDTV - Surf's Up. SPHE release. BD only.




And here is a simulated 100" image from a 1080p projector/HDTV - Die Hard 4.0. Fox release. BD only.




Notice the black bars at the top and bottom that some newbies always complain about. Seriously, we need to educate those newbies.

Owners of RPTVs, plasmas and LCDs have no way of changing the size of their screens. But owners of projectors can - by zooming in on the picture so that only the movie and not the black bars are presented.

A 100" image from a 1080p projector is counted diagonally. So that means for a 100" 16:9 image, the width is 87.2" and the height is 49". A Constant Height Screen is just that: using any aspect ratio, 16:9 or 2.39:1, the height is constant.

Here is a simulated image from a 1080p projector of a constant height setup with a height of 49".



As you can see, the picture is wider but the height stays constant. The width is now 127".

Here is a simulated composite image of Surf's Up and Die Hard 4.0 from a 1080p projector of a constant height setup with a height of 49".



As you can see, that's how a constant height screen is supposed to work.

Anyway, I became obsessed in trying to figure out a way to easily calculate the dimensions needed for the screen given any width, height or diagonal criteria. It took me a while but finally my subconscious math mind figured out the problem. So I created an Excel sheet and it works pretty well. If you don't have Excel, well...

Remember. Rename the file extension to .XLS once you've downloaded the .TXT file. The sheet is protected from accidental cell erasure. You can only enter the values of width, height and diagonal that you need to calculate. If you need to change the cells for whatever reason, you must UNPROTECT the sheet - Tools -> Protection -> Unprotect Sheet.


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[WriteSimply]

Fresh from Cedia, here's one D-ILA projector that can be used with an anamorphic lens for that perfect constant height screen. From AnandTech



30,000 contrast ratio without iris control. Sweet!

Originally Posted by AnandTech.com

Both projector feature a native contrast ratio of 30,000:1 without the use of a dynamic iris. Improvements in the D-ILA chips themselves, lens improvements and digital processing enhancements all contribute to the higher native contrast ratio compared to older JVC models.
...
Both projectors are 3-chip 1920 x 1080p D-ILA displays, and both support vertical stretch for 2.35:1 constant image height scaling applications. The DLA-RS1 required the use of an external video processor to do the same.
...The DLA-HD100 will be sold by JVC America, sold with limited production, no internet sales will be allowed - under $8K, shipments in November.

The DLA-RS2 will be sold by JVC Professional Products, MSRP at under $8K with shipments beginning in November. Like the HD100, the DLA-RS2 will be available through distributors and custom installer resellers, no internet sales will be permitted.

The two new projectors are identical, the only difference being which division of JVC sells it. Compared to their predecessors, we know that they are using new D-ILA chips but we're unsure as to whether or not the processors and optics are any different.

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[HDJK]

Interesting, thanks for that. Does that mean once you have set it up with a projector like those JVCs, that you don't have to adjust the lense if you want to watch Surfs up after watching Die Hard? Like having a 2.39 TV with a 'No stretch' option?

[WriteSimply]

Pretty much, yeah. JVC + anamorphic lens = constant height screen.

The JVC like other higher end projectors, like the Marantz I saw, can stretch 2.40 material vertically thereby using the entire D-ILA chip. The anamorphic lens then squeeze the video but on a wider screen and at the same height as your 1.78 screen.

A certain projectionist (hint, hint) told me that you don't necessarily need to use the technique above to achieve constant height. You can just zoom in the 2.40 picture to the same height and you got your own CHS setup. However, you then need to undo the zoom you did for 1.78 (16:9) material.

Regardless CHS is really something to behold for movies with AR above 1.78. POTC is just amazing!


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[HDJK]

Originally Posted by WriteSimply

A certain projectionist (hint, hint) told me that you don't necessarily need to use the technique above to achieve constant height. You can just zoom in the 2.40 picture to the same height and you got your own CHS setup. However, you then need to undo the zoom you did for 1.78 (16:9) material.

I remember Dezi writing about this a while ago, that's why I assumed you have to re-adjust something to go from 1.78 to 2.40. Would be nice if there were motorized zoom lenses with different memory points so you can just push a button once you have it set up

Originally Posted by WriteSimply

The JVC like other higher end projectors, like the Marantz I saw, can stretch 2.40 material vertically thereby using the entire D-ILA chip. The anamorphic lens then squeeze the video but on a wider screen and at the same height as your 1.78 screen.

This I don't quite understand. If that's what happens to 2.40 material, what happens to 1.78 movies? The lens is physically anamorph, isn't it?

Originally Posted by WriteSimply

Regardless CHS is really something to behold for movies with AR above 1.78. POTC is just amazing!

I bet it is

[Deciazulado]

Originally Posted by HDJK

This I don't quite understand. If that's what happens to 2.40 material, what happens to 1.78 movies? The lens is physically anamorph, isn't it?

You'd have to swing the anamorphic lens out of the way for 1.78 and smaller, or the 1080 x 1920 pixels can be squeezed onto 1080 x 1440 and you don't have to swing out the anamorph, but you lose quality on the 1.78 or lower programs.

[HDJK]

^^ I see, the anamorphic lens is an add-on. Now it makes sense. Thanks for the info

[WriteSimply]

And this is how an anamorphic lens add-on setup looks like with PJ.

From AnandTech.com. This is using Sony's latest VPL-WV60.

Note that this is an automated add-on.


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