Movable curved scope top masking? - AVS Forum
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post #1 of 12 Old 09-04-2014, 12:42 AM - Thread Starter
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Movable curved scope top masking?

Im going to build a curved scope screen but would really like to make at the same curved motorised top masking...
Ive been laying in bed dreaming what way to go, that's clean and simple.


I currently have a scope AT screen with motorised side masking so that's all covered, but I would like the top to move on the new screen.
The width is approx. 135" wide.


Hope someone here has made motorised "curved" top masking. .....

Last edited by Bob Sorel; 09-04-2014 at 11:06 AM.
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post #2 of 12 Old 09-04-2014, 07:56 AM
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Having trouble visualizing what you are asking. A scope screen implies a CIH setup and I can't think of what you would mask the top of the screen for. There will always be information at the top of the screen. Are you seeing distortion on your current flat screen?

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post #3 of 12 Old 09-04-2014, 01:36 PM - Thread Starter
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Originally Posted by jeahrens View Post
Having trouble visualizing what you are asking. A scope screen implies a CIH setup and I can't think of what you would mask the top of the screen for. There will always be information at the top of the screen. Are you seeing distortion on your current flat screen?


Its pretty simple, I want to vary the top height for different ratios and make 16:9 or 4:3 or 1.85 images larger at times. Many of the older 70MM films are not 2.35, they are much higher, when viewing these at CIH you crop the top all the time. Having movable top masking allows one to fix all these things. Just the same as many of the old cinemas with curved screens used to have, movable top masking as well as the sides.


I know how they do it in the cinema as I was a projectionist for 35+ years, just hard to implement in a smaller space. Im trying to find out here if anyone has done it motorised and curved.
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post #4 of 12 Old 09-04-2014, 03:09 PM
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Not to quibble, because you are certainly entitled to do whatever you want to do, but what you're proposing is not Constant Image Height (which by definition requires the image height to remain constant), but Constant Image Width with removable top and bottom masking.

Again, you have every right to set up your screen however you prefer, but this may not be the right forum to ask your question in.

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post #5 of 12 Old 09-04-2014, 03:18 PM - Thread Starter
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Quote:
Originally Posted by Josh Z View Post
Not to quibble, because you are certainly entitled to do whatever you want to do, but what you're proposing is not Constant Image Height (which by definition requires the image height to remain constant), but Constant Image Width with removable top and bottom masking.

Again, you have every right to set up your screen however you prefer, but this may not be the right forum to ask your question in.

Precisely you are dead right it is CIW, but I'm not looking for top and bottom masking to move. As I stated I'm wanting to do it as they did in 70MM cinemas, top and sides moving on a curved screen.


I will move my post to the screen forum.
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post #6 of 12 Old 09-04-2014, 06:42 PM
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How are you planning to make a curved screen work? Projectors are designed to hit a flat surface, if you project on a curved screen you'll be introducing focus and geometry distortions.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #7 of 12 Old 09-04-2014, 08:00 PM - Thread Starter
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Originally Posted by stanger89 View Post
How are you planning to make a curved screen work? Projectors are designed to hit a flat surface, if you project on a curved screen you'll be introducing focus and geometry distortions.


This is not the question....


Ive been using an Isco III for years, they work extremely well with curved screens just as they did in cinemas when Fox introduced the Robe.
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post #8 of 12 Old 09-05-2014, 05:40 AM
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I'm still confused because you won't get a taller than 2.39:1 screen shape with a lens in place. Maybe I'm still just not clear on what you're envisioning.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #9 of 12 Old 09-05-2014, 09:50 AM
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A CIW setup wouldn't really work with an HE lens, so I'm not sure what the thought is here. And as Stranger points out the geometry of the 16:9 panel with the projector in anamorphic mode dictates the picture size the lens will create.

You could put in a scope screen with top/bottom and side masking. For the few wider than 2.35:1 movies you could use the minimal top/bottom masking. And for 1:37/1.85:1 content the side masking. However 2.35:1 would still be the largest content. You would not have 1.37/1.85 content taller. Nor would greater than 2.35:1 films be wider.

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post #10 of 12 Old 09-05-2014, 01:00 PM - Thread Starter
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Quote:
Originally Posted by stanger89 View Post
I'm still confused because you won't get a taller than 2.39:1 screen shape with a lens in place. Maybe I'm still just not clear on what you're envisioning.
If you use the A lens for scope, plus zoom memory on the VW1100 you can create any size ratio you want. In that case you can have a huge 1.85 with movable top masking (if you want), simple.


Anyway I didn't come here to ask these questions, I was asking about making movable curved top masking....
I am in the wrong thread to get this answer and have now asked in a more appropriate thread.


Thread closed!
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post #11 of 12 Old 09-06-2014, 07:33 AM
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Quote:
Originally Posted by RapalloAV View Post
If you use the A lens for scope, plus zoom memory on the VW1100 you can create any size ratio you want. In that case you can have a huge 1.85 with movable top masking (if you want), simple.

Anyway I didn't come here to ask these questions, I was asking about making movable curved top masking....
I am in the wrong thread to get this answer and have now asked in a more appropriate thread.
Well the main problem is I (and I'm guessing everyone else based on the responses) isn't aware of anything like you're asking for. I can't even think of a horizontal masking system that only moves the top masking but I'm sure that's out there.

I understand everything you're trying to do, except why it has to be a curved screen. The only time (nearly) that a curved screen makes sense is in a CIH setup with an anamorphic lens. If you start zooming then the curvature is just a significant problem causer. If you zoom with the lens in place then the curvature will be incorrect for the effective throw introducing distortions. If you remove the lens and zoom without it, again, the curvature introduces distortions.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #12 of 12 Old 09-06-2014, 02:45 PM - Thread Starter
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Quote:
Originally Posted by stanger89 View Post
Well the main problem is I (and I'm guessing everyone else based on the responses) isn't aware of anything like you're asking for. I can't even think of a horizontal masking system that only moves the top masking but I'm sure that's out there.

I understand everything you're trying to do, except why it has to be a curved screen. The only time (nearly) that a curved screen makes sense is in a CIH setup with an anamorphic lens. If you start zooming then the curvature is just a significant problem causer. If you zoom with the lens in place then the curvature will be incorrect for the effective throw introducing distortions. If you remove the lens and zoom without it, again, the curvature introduces distortions.

How do you think all the thousands of cinemas cope to screen 1.85, 1.66, 1.33 on a curved screen?
Do you think they have an A lens in place to stop distortion?


Every cinema that has a curved screen all over the world will display some form of distortion when screening other formats besides scope. Does the audience notice that and complain, no! You see much more distortion in fact even on a curved screen when an A lens is in place, the lens itself creates its own complex distortions, even a curved screen doesn't remove it 100%.


The distortions when screening all the other ratios on a curved screen when the A lens is out of the light path is so minimal. In fact its impossible to see without a test pattern, and we all know that's not the movie we watch.


Even highly racked projectors in places like Radio City produce incredible distortion, the screen can NEVER be angled to match the rake of the projectors. If the screen did match the rake the people in the stalls would never see the screen. I have projected film in many cinemas with a rake that's so steep and the screen only has a minimal tilt backwards, did the audience ever notice the distortion, no.....


The only place where they tried for years to make this work was when Cinerama was over....
They tried to screen 70MM and 35MM onto that DEEPLY curved screen, the distortion was really bad and in the end they abandoned that. I was projecting film in that very last Cinerama theatre in Auckland as we struggled to screen 70MM and 35MM onto that deep curve.


The shallow curve used for scope is so minimal any distortion can only be picked up as I say with test patterns.....


Ive been in this industry a very long time. Ive seem many different screens flat and curved. Im picky and have a real keen eye for top notch film presentation, I know what works and what doesn't.


I don't want to dispute the pros and cons of ratios and curved screens vs flat screens. I came to ask a question, I asked in in the wrong thread, Im trying to get the answer to my question, and that's why I moved that question to another thread.....


Great to see you too have an interest in scope and A lenses.

Last edited by RapalloAV; 09-06-2014 at 02:48 PM.
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