# Anamorphic projection but NOT curved screen?



## DucatiR

During my reading over the last several months I have somehow come under the impression that anamorphic projection required a curved screen for pincushion projection. In a different thread I learned from Prof. that this may not be the case. I am creating this separate thread for my specific circumstance. Do I need a curved screen?

- BenQ W5000 projector (not purchased yet), ceiling mounted about 15-16' from screen.
- Acoustically transparent screen will be maximum 100" width, 1.2 gain (Seymour's new XD material).
- anamorphic lens

I have presumed a curved screen was required. But in a different thread (link below) Prof. had this to say:



Prof. said:


> The W5000 has a high TR., when set to zero zoom and from the projection distance and image size that you're looking at...
> This means that you will have minimum pin cushion and that you won't need to have a curved screen..
> I would just use a flat screen..


I don't intend to question Prof.,:hide: but I've had this curve requirement in my head so long I feel I need to ask the question again just to make sure before I proceed with construction of the screen wall.

My construction build thread:
http://www.hometheatershack.com/forums/home-theater-design-construction/13639-new-ht-project-construction-questions.html


Bruce Fisher's thread on anamorph & screen
http://www.hometheatershack.com/forums/anamorphic-projection/18774-check-my-numbers-please.html#post168814


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## Prof.

DucatiR,

Have you come to a decision on your screen yet?

I may be able to throw some light!  on your dilemma..

I've recently installed a new projector and made a bigger CIH screen..
I had some concerns with the new set up, as to whether I would need to go to a curved screen or not..
The problem was that the new projector needed to be closer than previous..even with the bigger screen..
This reduced my TR to a shade under 1.7..
Also the new screen is 8" wider, which makes for a very wide angle of projection..and I felt that the pinchusion might be excessive..

I decided to make a flat screen and hope for the best..If it didn't turn out suitable then I would have to make a curved screen..

The end result surprised me..Not only was the pincushion no more noticeable than previous, but the image sharpness right to the very edges was even better..even with that wide projection angle!!
Probably the better quality projector did have something to do with it, but it did show me that I didn't need a curved screen..

There is another disadvantage to using a curved screen that has some gain..
You do get a smaller viewing cone which will drop some light output when viewing on an angle..

But it does come down to personal preference..Some people use curved screens just for the effect, when they don't really need to have one..


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## DucatiR

Prof.,
Thanks much for that additional information. I've been monitoring the thread and concluded today, after 30+ views and no bites, that "Prof. has spoken! Silence = consensus!!" :bigsmile:

I've also seen a grid screen shot of the MK3 from the Australian sales outlet. 
http://www.anamorphiclens.com.au/
See the second thumbnail in the image grid near the bottom of the page - the test pattern. The pincushion effect can be seen in the lower and upper center edge of the screen but barely. Between your feedback, Chris' at Seymour and the sales people at ProjectorScreens.com I have concluded I will go with a flat screen. 

I'm now just waiting for Seymour to release the specs/prices on their new fixed frame products to determine if I go out of the box kit or DIY frame + Seymour fabric.

Thank you again Prof. You've saved me considerable design and construction headaches!:T

DucatiR


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## Prof.

DucatiR said:


> Prof.,
> Thanks much for that additional information. I've been monitoring the thread and concluded today, after 30+ views and no bites, that "Prof. has spoken! Silence = consensus!!" :bigsmile:


:rofl: I'm not the expert..Mark is, but I guess he's very busy filling orders for the new lens..



> Thank you again Prof. You've saved me considerable design and construction headaches!:T
> 
> DucatiR


Happy to help...


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## Bruce Fisher

Sorry - been busy working on my theater and hadn't checked in for a week or so.

I exchanged emails with Mark (Aussiemorphic) about this topic. His response (paraphrased) is "flat screens generally work fine and you shouldn't need a curved screen. However, curved screens look really cool! That said, most people don't see a pincushion effect and it should be fine for you. I'd suggest starting with flat and upgrade to curved later if you really find you need it".


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## getgray

Old thread, but I'm working on my new user post count so here some hopefully useful info:

I spec a lot of scope screens. Kind of my "break" point is a 1.8 TR. If the TR is < 1.8 I like curved screens. If >1.8 flat or curved. Long throw, flat. The curve counteracts pincushion (image bowing) which is an artifact of all anamorphics. 

I have a calculator that can determine the pincushion in a setup, and advise the "perfect" curve. However nless the user is going to be 100% scope viewing, I like a curve radius that is somewhere between flat and the ideal curve. That way, you sort of split the difference on the pincushion error.


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## Prof.

getgray said:


> I have a calculator that can determine the pincushion in a setup, and advise the "perfect" curve. However nless the user is going to be 100% scope viewing, I like a curve radius that is somewhere between flat and the ideal curve. That way, you sort of split the difference on the pincushion error.


Totally agree..I'm using a flat screen with a 1.9TR..There is some slight pincushion but not enough to have a curved screen..
If your screen borders are covered with a good quality black velvet (Fidelio and the like) you're not going to see the pincushion effect anyway..


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## Mark Techer

My decision to use the curved screen was also linked to the fact that I don't move the lens from the light path for the smaller ARs like 1.78:1. Whilst it is true that scaling for CIH throws away H-Rez for HDTV, I prefer to keep the correct geometry (straight horizontal lines) the curved screen gives. Because the curved screen corrects pincushion produced by the lens, removing the lens for HDTV now introduces barreling because the screen is still correcting for a problem that is not present. 

When I first curved my screen I was running an extremely short throw (1.3:1) and therefore the pincushion was unacceptable to me so curving the screen was a requirement, not an option. Now that I run a longer throw (2.1:1), I've had to reduce the curve (increase the radius) because there is still pincushion, though considerably less. 

This is my personal preference and not necessarily the best option for all CIH users.


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## Prof.

Mark Techer said:


> I prefer to keep the correct geometry (straight horizontal lines) the curved screen gives. Because the curved screen corrects pincushion produced by the lens, removing the lens for HDTV now introduces barreling because the screen is still correcting for a problem that is not present.


That's a good point Mark..If you never move the lens, then a curved screen is ideal..But if you prefer to move the lens for 1.78 viewing, then the best choice is a flat screen..
I might have to look into a curved screen!


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## Mark Techer

Prof. said:


> That's a good point Mark..If you never move the lens, then a curved screen is ideal..But if you prefer to move the lens for 1.78 viewing, then the best choice is a flat screen..
> I might have to look into a curved screen!


Again, that would depend on the amount or Scope Vs no Scope program being watched. In my theatre, over 90% is Scope, so even if I was moving the lens for non Scope, I'd still want to have a curved screen.


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## Prof.

Hey Mark,
Are you under any threat from these rising flood waters in Brisbane?
I've just heard that the flood level could be higher than the '74 floods..That's incredibly serious!!
Yesterday we saw the amazing vision of cars floating down the main streets of Toowoomba like corks, crashing into each other and sinking beneath the torrent!!:yikes:


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## Mark Techer

Prof. said:


> Hey Mark,
> Are you under any threat from these rising flood waters in Brisbane?
> I've just heard that the flood level could be higher than the '74 floods..That's incredibly serious!!
> Yesterday we saw the amazing vision of cars floating down the main streets of Toowoomba like corks, crashing into each other and sinking beneath the torrent!!:yikes:


Hi Prof,

Fortunately I live on a hill, so if I get water here, the rest of Brisbane is gone. Yes, this is serious and I could not believe what has happened out at Toowoomba. That water is of course making its way to Brisbane and with high tides preventing the excess water going out to sea, the Brisbane river has no choice but to break its banks. I'm told the worst is yet to come, maybe Thursday. 

Mark


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## Prof.

That's good to hear that your on a hill..
It looks like there's going to be some serious flooding by Thursday and I hear Ipswich is in serious trouble as well and mass evacuations are underway!


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## Mark Techer

It situation in the city and low lying surrounding suburbs is getting bad with the worse still to come. This will certainly change the lives of many and is a dark time for our beautiful city.


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## Prof.

Yes..I've been watching it very closely and the devastation is unbelievable!
To see all that stuff floating down the Brisbane river and being destroyed as it tried to pass under bridges, including the floating restaurant was incredible!!
And then to see how many suburbs have been affected..it's just mind blowing..
Having lived there for 12 years, I know and have been to a lot of those places..


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