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Discussion Starter · #1 ·
We are about to purchase a new home and I am planning to build a Dennis Erskine designed theater in the basement. I discussed screens with him briefly and he really got me thinking about putting in a 2.35:1 screen in a constant-height scenario. In other words, 2.35:1 movies will fill the entire screen and lesser aspect ratios (1.78 and 1.33 primarily) will fill the height of the screen and be masked appropriately on the sides using motorized drapes - just like a real commercial movie theater!


Actually implementing a constant-height 2.35:1 screen is pretty difficult for a fixed panel digital projector, and to make matters worse I had some very important constraints that had to be satisfied:


1) Switching between aspect ratios MUST be possible with the touch of a button on a remote.

2) I would like to use as much of the resolution of the projector as possible in each mode.

3) Zooming/refocusing the projector is not an option. DILARD does provide some mechanism for automating these features but I just don't think it is accurate enough for my purposes.


I was browsing the AVSForum boards and found a really interesting idea that William came up with. This is to use an ISCO II lens *only* for 2.35:1 movies and to "slide" it out of the way for all other aspect ratios. Let me summarize what this means below:


1) Set up the projector to use the middle 768 pixels of the panel (1365x768) and calibrate it to fill the center 16x9 area of the screen (filling the height, but not the width). The image must be centered horizontally in the middle of the screen.


2) Use the excellent aspect ratio capability of the TheaterTek DVD player to set up aspect ratios for 4x3, anamorphic 16x9 and letterboxed 16x9. These will all be projected as-is without the ISCO II lens in place.


3) Now, mount the ISCO II lens on some sort of an assembly that can be slid out of the way of the projector. I don't actually have an "automated" solution for moving the lens yet, but I'm sure this is doable. I hope Dennis will have some ideas on this.


4) With the ISCO II lens in front, the projected image is now stretched horizontally to fill the screen. Set up another two aspect ratios in the TheaterTek DVD player for dealing with letterboxed 2.35:1 and anamorphic 2.35:1 DVDs.


This completely solves my DVD problem. I'm only ever using 1365x768 pixels on my panel, but I'm willing to sacrifice that for the relative ease of achieving what I have described.


By the way, everything I desribed above was William's idea and I'm not taking credit for any of it.


Ahh, but what about for HDTV? I would ideally like to do the exact same thing for input from my DTC100, HiPix, or JVC HM-DH30000U VCR. The problem is that I don't have the flexible aspect ratio control that I do with TheaterTek, so I need to make the projector do the work for me.


At first I was thinking that I would need to come up with a way of having two 1080i memories for each of the HD inputs (Computer 2 and Component). I don't believe there is any way to do this (I tried playing around with "overloading" the 720p input but that had strange consequences).


Then I realized that there was a *simple* solution to my problem already built in to the projector. It was so simple that I almost overlooked it entirely. It doesn't involve any projector mods whatsoever. Here it is:


1) For standard 16x9 HDTV, put the 1080i input on the projector in 16x9 mode. Keep the ISCO II lens out of the way (just as with DVDs). This projects a 16x9 HD image in the center of the screen filling the height.


2) For 2.35:1 HD movies, put the 1080i input on the projector in 4x3 mode (which stretches the black bars on the top and bottom of the image off the visible screen - which is the middle 768 pixels of the array). Also, slide the ISCO II lens in place which stretches the image out horizontally and fills the entire 2.35:1 screen - NO BLACK BARS!


That's it! If I can come up with some sort of motorized way of moving the ISCO II in and out of place I'll be set and have very little configuration to do.


I also thought of a really cool idea but I don't know if it would be possible or not. It would be great if you could have a script on the HTPC do the following when a DVD is inserted:


1) Look up the DVD on DVD Profiler (using the same mechanism DVD Profiler does) and read the aspect ratio of the movie from the database.

2) Use Girder to automate setting up the aspect ratio with no user intervention. It could make sure the projector/amp/preamp are on, move the drapes, slide the ISCO II lens into place if needed, and switch the aspect ratio inside TheaterTek.


Ah well, it sounds cool to me and would definitely improve the WAF of the new theater. It could be as simple as pop in a DVD and everything comes on and sets itself up properly.


Any comments/suggestions on the scheme above are welcome!



-Dave
 

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All good ideas, Dave.


I'm looking at creating a very similar setup, so I am very interested in working out the ideal scenario.


The only issue I see is that you desire to use the middle (vertically) portion of the panel. As I understand it, the center of the DILA's lens is exactly even with the bottom of the projected image. This means that as you zoom, the bottom of the image stays at a constant height and the top changes. I'm guessing you are looking at a celing mount setup, so the opposite is true. Meaning, the top of your picture will be constant and the bottom will change as you zoom.


Because of this, mounting both your pj and and screen can be greatly simplified if you use the top (or bottom, depending on how you mount) of the panel instead of the middle. This can be easily setup using Dilard.



I've already begun some brainstorming on ways to automate moving the ISCO. It should be quite simple. I do automation for a living and have some small controllers with inputs and outputs on them and a RS232 port. Using a tri-state (open/off/close) actuator and a little bit of code running in a PC, this can be done. Just need to find a track with rollers or bearing that would mate with the rail on the lens. But, I'm trying to think of a better, simpler solution. If one was willing to live with a wall switch to change lens position, this would be a piece of cake. Automatic selection based on inserted disc requires the PC and makes things a bit tougher.


-jp
 

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Discussion Starter · #3 ·
You are absolutely correct, and I had thought about that but forgot to mention it in my post. First of all, the reason I chose the center portion of the panel is that my solution for HD on 2.35:1 screens will require using the 16x9 HD mode built into the projector. This centers the image in the middle of the screen. It is possible there is some way to modify the 1080i input to reposition it in both 4x3 and 16x9 modes (I'd need to shift it up 128 pixels in both modes). If that were true then I could go with a top-aligned image.


However, my solution in my current proposal is to make sure the center of my projector lens is 1/6th of the screen height higher than the top of the image. If I go with a 5 foot high screen I would have to have the projector 10 inches higher than the top of the screen. This should be doable.


If anyone can suggest a way that I can keep the image aligned with the top of the panel instead of the middle I'd appreciate it.


I look forward to hearing how you end up automating moving the ISCO. My theater won't be done for 3-4 months so I still have plenty of time to do research.


Thanks for the reply.


-Dave
 

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I just bought a Runco VX1000C DLP (which doesn't have the flexibility of the JVC D-ILA units) and was wondering how I could set up a constant height/variable width 2:40:1 "scope" screen, too. But I have given up on the idea and will simply go with an electric screen that horizontally masks to 2.35:1 and I will optimize my seating positions for 2.35:1 presentations (really 2.40:1 in most cases, I'm told by posters on the screen forum).


1.85:1 and 1.78 DVDs will be too big at that seating distance, admittedly, but 16:9 HDTV should be OK (if still just a bit too large) because of the greater resolution and better colors. Of course, if I had a back row, I could just move there when not watching "scope" movies!
 

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I originally designed a 2.35 aspect constant height with Dennis.


It is a great set up.


Having to do anything manually (e.g. sliding an ISCO lens) was out of the question for me. The ISCO cuts the throw distance some 25%. I didn't want the PJ anywhere near the viewing area. Hushboxes work well and can be esthetically pleasing but in the middle of a tray ceiling...............no!


Thus, I went with the Panamorph (no change in throw distance). The PJ is mounted in the equipment room immediately behind the theater (for loudness and esthetic reasons).


I recently went back to the drawing board and decided to mate a JVC G-15 with a Panamorph on a 16:9 screen and using a Stewart Horizontal Masking system.


The reason?


What botherred me about the constant height is when you move to the 1.78 and 1.85 aspect ratios from the 2.35, you lose 20% to 25% of the screen width and a sizeable amount of vertical height - in other words, the picture shrinks considerably.


It is all about picture size to me. The Stewart masking allows me to switch between aspects whilst maintaining the same width with perfect masking for any widescreen aspect ratio (up to Ben Hur and 2.76 if I want). Changing the masking is done via IR (I'll grant you it is a manual stroke of the button to accomplish the mask movement).


In addition, my screen is perfed. If all three speakers were behind it, the drapes moving inward to mask the 1.78 or 1.85 pictures would mask the L and R speakers, too (note: I actually moved the speakers forward and to the sides of the screen behind acoustically transparent false walls anyway).


Since I'll be using a scaler (as yet undetermined) and the Panamorph, there is no need to manually do anything except change masking (via remote).


As for the little to be used 4:3 aspect picture, the motorized drapes will close in to properly mask the vertical portion of that picture.


Just some thoughts.


Jeff
 

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Quote:
What botherred me about the constant height is when you move to the 1.78 and 1.85 aspect ratios from the 2.35, you lose 20% to 25% of the screen width and a sizeable amount of vertical height
If you are losing any height, than by definition, you don't really have a "Constant Height" setup, do you? :rolleyes:


I'm not sure whay kind of setup you have, but I know for sure it's not "Constant Height" because on a real "Constant Height" setup the height is "Constant". :(


Also, the whole idea of a "Constant Height" setup is to preserve the cinematographers intention of a 2.40:1 movie being wider than a 1.85:1 movie, not shorter.


Vern Dias
 

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Vern,


If you read more carefully, my set-up is a constant width.


Masking moves up and down in the vertical plane.


The width of my screen is at a constant of 118". Vertically, the screen will mask to any aspect with the 118" width.


Jeff
 

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Here is the first line in your post:


"I originally designed a 2.35 aspect constant height with Dennis."


You never explicitly stated that you abandoned that design, but the fact you chose a Panamorph should have been a flag to me.


Sorry....


BTW, this is still an incorrect staement:


"What botherred me about the constant height is when you move to the 1.78 and 1.85 aspect ratios from the 2.35, you lose 20% to 25% of the screen width and a sizeable amount of vertical height - in other words, the picture shrinks considerably."


The height does not change.


Vern Dias
 

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Vern,


You are right, my errror, the height does not change.


Jeff
 

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Quote:
Originally posted by thebland
....What botherred me about the constant height is when you move to the 1.78 and 1.85 aspect ratios from the 2.35, you lose 20% to 25% of the screen width and a sizeable amount of vertical height - in other words, the picture shrinks considerably....
As I stated before in a your previous thread Is it possible to eliminate black bars on all aspects from 4:3 to 2.35? You have it backwards. You will lose 33% picture size by using constant width. If you have a 118" screen your 1.78 picture size will be 118"x66". With a 2.35 picture your picture size will shrink to 118"x50" which is 33% smaller. So the technically larger (33% wider) 2.35 picture will in fact be smaller (33% shorter) than the technically smaller (narrower by 33%) 1.78 picture. Remember 2.35 IS wider than 1.78 and in a perfect world you should lose picture size (width only) when switching from 2.35 to 1.78. Not the other way around. I guess you will not understand this until after you have your screen in place.
 

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William,


I think we are miscommunicating.


You are relerring to absolute picture size being lost. In that you are correct.


I am referring to relative picture size - meaning that in a constant width set up my picture width (hence, relative size) will not decrease between the widescreen aspect ratios because the screen width doesn't change). Each aspect will be 118" wide in my case though vertically shrunken at the 2.35 aspect.


In a constant height, the overall picture size (width) will shrink moving from 2.35 to 1.78.


Yes I will lose some vertical picture height moving from 1.78 to 2.35 but, overall, widescreen pictures will be bigger in this type of set up.


Jeff
 

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I decided on a constant height for one reason, the wide-screen formats will have a greater screen size than the standard 4:3. When I go to 1.78 my screen will grow and for 2.35 it will grow again. I want my movies, and Hd to look better and bigger than just Tv video. I haven't made the mechanicals yet to move the ISCO II, but it will be similar to a garage door opener in switching and use of a screw...
 

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Jeff,

I have to disagree with some of your conclusions about picture sizes vis-a-vis constant height vs constant width. As William said, you might understand better once you have screen in place.


I had a 16:9 constant width (w/masking) screen before switching to a 2.35:1 constant height screen. For me, since I mostly watch DVD's and some HD (HBO/SHO on DISH.), I found that most of the picture I project (95% movies) ARE bigger with the 2.35:1 screen than on the 16:9 screen in which they would have been letterboxed.


I should also mention a more practical reason why a constant height setup is ideal: Most people will find that their HT room is height limited, in my case my basement is about 7'-6" high. If the goal is to get the biggest picture size, then the widest screen possible can be attained with a scope screen of some kind.


Getting back to the topic of the thread...


Dave,

It seems to me that things should work out well based on your more detailed description of what you want to do.

The only issue to look more into is that the DILA does not allow you to control the AR (4:316:9) unless you are using one of the 'Video' sources - i.e HDTV. However this might not be an issue for you.

Lastly, you should be able to use the same input, say Computer2 and two different sources say HDTV1 and HDTV2 for 1080i settings. Use Dilard's image geometry wizard to 'copy' the settings of the 1080i memory to the 720p memory.


Andrew.
 

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Quote:
Originally posted by thebland
William,


I think we are miscommunicating.


You are relerring to absolute picture size being lost. In that you are correct.


I am referring to relative picture size - meaning that in a constant width set up my picture width (hence, relative size) will not decrease between the widescreen aspect ratios because the screen width doesn't change). Each aspect will be 118" wide in my case though vertically shrunken at the 2.35 aspect.


In a constant height, the overall picture size (width) will shrink moving from 2.35 to 1.78.


Yes I will lose some vertical picture height moving from 1.78 to 2.35 but, overall, widescreen pictures will be bigger in this type of set up.


Jeff
Jeff,

Not sure why I keep trying to get you to understand aspect ratios. Maybe I just like the challenge. ;) First you will not have constant width or constant height with your setup but a compromise of the two. 1.33 (88"x66) to 1.78(118x66") will be constant height. 1.78 (118x66") to 2.35 (118"x50") will be constant width. Second 2.35 at 118"x50" is a full 33% smaller than 1.78 at 118"x66". Not the same and not larger but 33%smaller relative or absolute. Your statement that "In a constant height, the overall picture size (width) will shrink moving from 2.35 to 1.78." is 100% correct and moving from 1.78 to 1.33 the (width) will shrink the same amount again (-33%). This is what aspect ratios are about. The lower aspect number will have less width and be smaller.


So for you setup to be technically correct you should have the following picture sizes. 1.33 at 88"x66"(33% smaller and narrower than 1.78) - 1.78 at 118"x66" (33% wider and larger than 1.33 and 33% narrower and smaller than 2.35) - 2.35 at 155"x66" (33% wider and larger than 1.78)
 

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Quote:
Originally posted by dknight


If anyone can suggest a way that I can keep the image aligned with the top of the panel instead of the middle I'd appreciate it.
Dave,


The D-ILA can easily be programed to do the above.


It's "duck soup" for Mark Hunter's [ aka milori ] DILARD program. You can get DILARD projector mods to do just

what you want at:

http://www.dilard.com/dilard/download/mods.asp


Greg
 

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dknight-


I think you are on the right track. I switched from 16:9 to a constant-height 2.35:1 setup, and it was the best change I have made. The appearant size of the image does not seem smaller when I display 16:9, nor does the 2.35:1 image seem bigger. 2.35:1 is WIDER, as it was meant to be.


I know that probably sounds dumb, but I have used my HT both ways, and fully endorse constant height.
 

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Quote:
Originally posted by Jeffrey
dknight-


I think you are on the right track. I switched from 16:9 to a constant-height 2.35:1 setup, and it was the best change I have made. The appearant size of the image does not seem smaller when I display 16:9, nor does the 2.35:1 image seem bigger. 2.35:1 is WIDER, as it was meant to be.


I know that probably sounds dumb, but I have used my HT both ways, and fully endorse constant height.
Some time ago I remember a thread where a person demonstrated a constant area wide-screen display. This seemed to be an alternative to the constant width vs. height question. Anyone else remember this and is it a good alternative or is it too difficult to implement.
 

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Bjoern Roy is our AVS "Constant Area" maven. Do a search on his name for his posts about his magnificent set up and go to his website for pics and more information. But note: he uses an NEC XG135LC CRT projector which makes things quite a bit simpler, I'm gathering.
 

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Discussion Starter · #20 ·
I really didn't want this thread to degenerate into a constant-height vs. constant width/area discussion thread. There are plenty of those already on this board. If you're interested, please try doing a search through the archives for 2.35 or constant height.


Midi-guy: Last night I tried doing what you suggested (creating two 1080i memories on comp2 using HDTV1 and HDTV2 slots). It actually worked, with one minor caveat. You can't directly switch between the two memories or the projector won't resync. You need to first switch away to another input (e.g. comp1) and then back to the new memory and it will work.


So I ended up with the following memories:


HDTV2: 16x9 1080i top aligned that will fill the center (16x9) portion of my 2.35:1 screen.


HDTV1: 4x3 1080i that is shifted up 128 pixels (the exact size of the top black bar on a 2.35:1 HDTV image). When used with an ISCO II lens it will properly stretch the inner portion of a 2.35:1 HD image and be top aligned (no black bars). The top 128 rows of pixels are actually shifted to the bottom of the image, but since they are just black bars it is equivalent to having those pixels turned off.


Thanks for all suggestions, everyone. I'm still interested in whether or not I could automate the aspect ratio selection using DVD Profiler data when a DVD is inserted, but I'll post a separate request on that in the HTPC forum.


-Dave
 
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