If torus is so good, why was the Novabeam screen so bad? - AVS Forum
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post #1 of 9 Old 06-27-2001, 09:31 AM - Thread Starter
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Years ago I remember seeing turus screens on a Kloss, and much more recently on a Sony (both CRT) and both had HORRIBLE hot spotting...what gives? Has screen material improved that much or what?

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Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

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Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #2 of 9 Old 06-27-2001, 12:54 PM
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*Design* has improved. The principal advantage of a TORUS screen is that it is optimized for each installation, the principals are not different than a Novabeam, but the screen is not general purpose and is optimized for one room. The screens you saw did not have enough curvature for the gain of the screen. They probably tried to go with a very high gain surface because the projector was rather under-powered for the size of screen and the curvature of the screen could not accomodate the high gain.

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post #3 of 9 Old 06-29-2001, 11:06 PM
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Ok Kam,
I will bite.as the gain climbs from 3/4/6/12 how much curvature is required to keep pace?
http://www.avsforum.com/ubb/smile.gifTD is 13-14ft as a starter.

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post #4 of 9 Old 07-02-2001, 10:02 PM
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Jeff,

The Kloss was not a TORUS, it was a section of a sphere (like the Vutec in the other thread), the problem with the Kloss was that the projector was so dim that screen had to do all the work and you got comparatively bad results. Where did you see the Sony CRT? As far as I know there are *very* few TORUS installations in home theatre applications (and I think Peter has probably tied up more than half of them). The screen may have been curved (it may even have been curved in two dimensions), but it may not have been a TORUS. The TORUS CCS name really reflects the design work that went into the screen as well as it's distinctive shape.

Ron,

The answer is: it depends. http://www.avsforum.com/ubb/smile.gif Different types/brands of screen surfaces have different fall-off characteristics and require different curvatures. It also depends on how much light you can afford to lose in the corners, for example if you were willing to accept 10% brightness loss in the corners you might be able to bump the gain up a little for a given curvature. It also depends on the seating positions of your audience, if they are very spread out you will need a larger curvature radius and a smaller gain. There's some justification to the design fee that Sigma charges, a lot of experience is involved. How much light loss in the corners is acceptable, how much will give visible hot spotting? The math required to determine the curvatures is not insurmountable, but I doubt many people have the experience to determine the other factors involved.

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Kam Fung
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post #5 of 9 Old 07-02-2001, 10:46 PM - Thread Starter
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The sony was about 7-8 years ago when I first got into FP. It was a used model in someones house. I dont know the screen brand, but for that time the owner tried to use the same pricipals of light control and sound deadening technology we use today. The screen was probably 100" diagonal or less, and was very washed out with hot spotting.

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Jeff
Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

Thanks,

Jeff

Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #6 of 9 Old 07-03-2001, 09:02 AM
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I don't think the screen was a TORUS then... A properly designed curved screen should not have any visible hotspotting. TORUS screens rarely (never?) go into anything other than a dedicated installation. The TORUS costs $10k+ with the design fee, so I doubt most people using one have a used projector...

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Kam Fung
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post #7 of 9 Old 07-03-2001, 10:49 PM
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Kam,
This is why we need a little(or a lot)of "cut and try."
Curved members please stand up and be counted.We need your measurements and observations.NOW!
http://www.avsforum.com/ubb/smile.gif

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post #8 of 9 Old 07-04-2001, 09:02 AM
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Like anything else....where can I see one in action?

My HT


iRule rules my theater
 

"If she's amazing she won't be easy,if she's easy she won't be amazing"

 

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post #9 of 9 Old 07-05-2001, 10:17 PM
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Art,

As I mentioned in another thread, any AMC theatre with the HITS (High Impact Theatre System) will be a TORUS screen. Enjoy!

Regards,

Kam Fung
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