I've been thinking more about getting a curved screen as of late. In speaking to Stewart about it, only about 1% of the screens they sell right now are curved. However, they expect to see a huge increase in curved sales, possibly getting as high as 20% of their business within the next year or two.

I also understand that Dennis (HT guru) installs a ton of curved screen in higher end rooms.

As I understand it, curved screens work particulary well with scope set ups (another huge trend) and with higher gain screens but if I'm misguided on this, please let me know.

I'm trying to fully understand the benefits and drawbacks of such a set up and that is what I would like to have this thread discuss. Let me start with some comments and questions. I'd really like to hear from those that have a curved screen or have seen one.

The benefits I see with the curved screen are as follows:
-reduced hot spotting with gain screens
- screen curve avoids cross reflection (all projected light is transmitted to the audience)
- looks "cool"
- improves image uniformity

Drawbacks?
-Added cost
-difficulty in figuring out optimal curve radius
- not sure about impact on viewing cone - expand it from the far side but reduce it from the near side?

Miss anything?

Your benefits are well stated except that, the curve will also resolve any pincushion resulting from the projector and lens combination. There is not a negative impact on the viewing cone in a residential space unless the room is very significantly wider than the screen.
they expect to see a huge increase in curved sales, possibly getting as high as 20%
Durn. I forgot to negotiate a royalty agreement. Nuts. ;)

Have an update. After speaking to a Stewart product expert, he reminded me that this screen will remove pin cushion effect with an anamorphic lens.

He also said that it effectively widens the viewing angle. I was originally concerned about loss of viewing angle on the near side but it's not a factor because the radius is not high enough to offset the adavantage of the viewer being directly in front of that portion of the screen. You do gain on the far side because of the angle of the screen.

EDIT: didn't see Denis's post before I submitted this

In terms of determining the correct radius, it depnds mostly on your anamorphic lens of choice. So in my case, I will contact Prismsonic to get the info that Stewart will need to determine approriate radius.

Other interesting fact is that the non-masked version of the screen is far less expensive than the cine-curve screen so give up hope if you saw that $18k quote. Further, given the structure of the screen, lace and gromut, it will likely be relatively easy to wedge in some masking. BTW, the screen border with this method of fixing the screen to the frame is 6". This screen must look realy cool!

What about Torus screens? I would like to consider a 2.35 or 2.05 screen in my new room but my projector is a CRT and I will be going the torus route. When a scope screen is masked down for 1.78 or 1.85 material doesn't it affect the hotspotting and color shifting?

What about Torus screens? I would like to consider a 2.35 or 2.05 screen in my new room but my projector is a CRT and I will be going the torus route. When a scope screen is masked down for 1.78 or 1.85 material doesn't it affect the hotspotting and color shifting?

Hi GScott, I'm still learning about all of this and I am not familiar with the Torus screen. Who makes it?

I'm not sure about the answer to your second question. Hopefully others will pipe in on it.

The Torus screen is a DIY screen that usually uses 3.1gain material that is around 5$ per square foot. It is best suited for CRT's because of the high gain. The Torus is curved with there being about a 9" depth difference from the center to any corner. The Torus is usually a near air tight curved "box" with a fan sucking air out to stretch the screen, which gets rid of wrinkles. Search "torus" in the CRT projector section or sceen section.

The Torus screen is a DIY screen that usually uses 3.1gain material that is around 5$ per square foot.
...and can have a serious adverse impact on room acoustics.

Dennis,

What makes a torus worse than a standard curved screen? Thanks.

Gary

It becomes an acoustical concentrator due to its shape, pointed pretty much right at the prime viewing location. As such it will pick up room reflections and beam them at the viewers location.

Vern

Imagine you are projecting onto your DirecTV satellite dish and sitting where the LNB is.

Gary:

Vern and Poindexter have it nailed. The effect is very audible and rather ugly.

Other than reducing pin cushion, what is /are the advantages of a curved screen ?

Art

Other than reducing pin cushion, what is /are the advantages of a curved screen ?

Art
Hi Art, added benefits include:

-widens viewing cone - particularly useful for those with a high gain screen

-Reduces/removes hot spotting

-More uniform color

-screen curve avoids cross reflection (all projected light is transmitted to the audience) enhancing perceived contrast especially if screen is close to the wall or walls are light colored

- Looks cool :)

What if the screen is curved only slightly, like in this thread : http://www.avsforum.com/avs-vb/showthread.php?t=541964

Will the sound reflection still be "very audible and rather ugly" -Dennis

Gary:

Vern and Poindexter have it nailed. The effect is very audible and rather ugly.

So needless to say, Torus is an acoustically reflective hard material - yuk. As it is, I don't even like a regular screen between myself and the diffusors at the front of the room because of the slap echo it creates - although it's a very minor issue in the grand scheme of things.

Dennis or others - any disadvantages?

When going from a 16:9 screen to a scope screen, I loved it and would never go back to 16:9. How about you folks out there that have gone to a curved screen - would you ever go back, why or why not?

What if the screen is curved only slightly, like in this thread : http://www.avsforum.com/avs-vb/showthread.php?t=541964

Will the sound reflection still be "very audible and rather ugly" -Dennis

I wouldn't do it because from what I undersatnd, the radius of the curve is important to the implementation of an effective curved screen. If you compromise on that, you may not like it plus you have compromised your audio. In terms of audio, I have a curve at the front of my room but it's the opposite of what the Torus is because you want to diffuse the sound not gather it and beam it at the listener.

Well I don't have a whole lot of pluses to add, as Dennis and your Stewart contacts seem to have them all listed. But as an owner of a Stewart curved, 2.35:1 screen, I thought I'd tell you the reason I went with it.

I have a CRT projector (9pg extra) and wanted a 9' wide screen. Don Stewart, while encouraging me to go a bit smaller, recommended the curved screen and higher gain material if I was set on a screen that large.

I'm glad I went with the curved/higher gain material and the 9' width. I'm sure that HAD I gone smaller the image would probably have looked even better than it does now (which in my opinion is awsome.) But I've never had anyone, who has seen it, say that it was dim. Far from it, in fact. And this is running it with a only average brightness and contrast levels.

And yes the coolness factor of the curved 2.35 screen is incredible.

So, in conclusion, you might want to add something along the lines of: Larger screen widths can be used, because the curve helps eliminate some of the problems that using a high gain screen can cause. Especially with CRT projection.

Ah, I see. The reason I asked is that these seem now ill suited for CRTs and since light output on so many fixed pixel devices didn't seem like an issue I though a flat screen would have done as well. Thanks !

Art

Well I don't have a whole lot of pluses to add, as Dennis and your Stewart contacts seem to have them all listed. But as an owner of a Stewart curved, 2.35:1 screen, I thought I'd tell you the reason I went with it.

I have a CRT projector (9pg extra) and wanted a 9' wide screen. Don Stewart, while encouraging me to go a bit smaller, recommended the curved screen and higher gain material if I was set on a screen that large.

I'm glad I went with the curved/higher gain material and the 9' width. I'm sure that HAD I gone smaller the image would probably have looked even better than it does now (which in my opinion is awsome.) But I've never had anyone, who has seen it, say that it was dim. Far from it, in fact. And this is running it with a only average brightness and contrast levels.

And yes the coolness factor of the curved 2.35 screen is incredible.

So, in conclusion, you might want to add something along the lines of: Larger screen widths can be used, because the curve helps eliminate some of the problems that using a high gain screen can cause. Especially with CRT projection.

Love your theater and the screen does look very impressive! I'm curious, did you have frame options?

The reason I ask is that the Stewart guy I was talking to said that they normally suggest securing screen with lace and gommat which results in a 6 inch border. Your border looks closer to 3 inches.

Thanks for the kind words.

My frame is just a little over 1.5 inches. The back of the frame, and front of the screen material has, for lack of a better term, buttons. They are spaced about ever 4 inches. Very secure and keeps the screen very tight.

Ah, I see. The reason I asked is that these seem now ill suited for CRTs and since light output on so many fixed pixel devices didn't seem like an issue I though a flat screen would have done as well. Thanks !

Art

Art, I have two primary motivations to go curved

First, I want reduce/remove hot spotting. On a 120" wide sope screen, Ruby is not bright enough and I don't want to go with a DLP 720p 3 chipper so I need a 1.5 gain screen. I hate hot spotting so I don't think this high gain screen would be a realistic option for me without the curve.

Second, to have more of the light from the projector come back to viewers and not bounce off of the sidewalls. I don't want to paint my walls black and so I view this as the next best thing to increased perceived contrast.

The pin cushion benefit is only minor because I use a long throw. The other benfits are "icing on the cake".

the biggest disadvantage for some of us is it requires a fixed screen; many of us must use a motorized roll-up

ken

effective curved screen. If you compromise on that, you may not like it plus you have compromised your audio.
I haven't compromised the audio with a curved 2.35:1 screen. Due to the width of the screen and the required subtended speaker angles for a good sound stage, the speakers are behind an acoustically transparent screen. That acoustical transparency doesn't allow the screen to act as a 'lens' nor contribute to slap echo in the room.

Note as well. A torus is like a segment of a sphere. The curved Stewart screens are like a segment of a cylinder.

Does anyone else see the irony in a curved screen....

for years we all screamed for flat screens as all CRT manufacturers could produce was curved (albeit the other way!) screens.

now.. with 2.35:1 in the home the tables have turned and its curve time!

now.. with 2.35:1 in the home the tables have turned and its curve time!
Nah. We went from convex, to flat, to concave.

Here is the reponse I got from Prismsonic regarding the question of appropriate radius using their anamorphic lens:

[I]"This really depends on so many things that it is impossible to say any number. However, I have experience of curved screens. I made one from the painted mdf plate. From that I can say that you don't need to have an exact radius, in order to get a good result."[I]

Hmmm, not exactly the response I was hoping for.

Dennis, I'm assuming that you will disagree with the above statement but please confirm. I would assume that the correct radius is needed to fix pin cushion. Is the correct curve radius also a function of screen gain?

...and can have a serious adverse impact on room acoustics.

I imagine a curved screen could impact acoustics too. I think you need to compensate for either, less so for a curved screen than the torus, however the torus does add a huge improvement in image quality, especially with CRT.

It is always surprising to me that we haven't placed speakers behind a Torus yet. I don't think it'd be that hard to maintain the vaccuum w/ an acoustically transparent screen.

I imagine a curved screen could impact acoustics too.
Nope. I use an acoustically transparent screen. A 2.35:1 will require all the speakers be behind the screen if you have the view angles correct.

Torus cannot have an acoustically transparent screen due to the vacuum required.

I made one from the painted mdf plate.
I would find that disconcerting. If one's business is high quality optics for projection systems, I'd be really nervous when a home made screen is what they are using.

the biggest disadvantage for some of us is it requires a fixed screen; many of us must use a motorized roll-up

ken

It also makes it difficult for masking systems and impossible for 4-way masking systems.

I had to make the choice between curved and masking and I chose masking instead. Since I was running a low gain screen, the hot spotting wasn't an issue, nor was the viewing cone problems, as the .95 gain Screen Research screen was actually brighter at the edges than a flat Stewart 1.3 gain screen.

While I see a few posts from one person that the curved screen "looks cool" I think that the 2.35:1 screens look cool period and don't need a curve to put them in the cool clique.

...but on a 2.35:1 you don't need top/bottom masking..only side masking.

BTW, if you're using a Screen Research screen, take a piece of 1" fiberglass, cut to the outside size of the speaker, cut cutouts for each of the drivers and install on the face of each speaker.

Hi Art, added benefits include:

-widens viewing cone - particularly useful for those with a high gain screen

-Reduces/removes hot spotting

-More uniform color

-screen curve avoids cross reflection (all projected light is transmitted to the audience) enhancing perceived contrast especially if screen is close to the wall or walls are light colored

- Looks cool :)


Bingo!
I could have not said it better myself.
Regards,
Don

I imagine a curved screen could impact acoustics too. I think you need to compensate for either, less so for a curved screen than the torus, however the torus does add a huge improvement in image quality, especially with CRT.

It is always surprising to me that we haven't placed speakers behind a Torus yet. I don't think it'd be that hard to maintain the vaccuum w/ an acoustically transparent screen.

After building over 800 large torus screens for commercial and motion picture exhibitors I would like to make the following comment. Theoretically, you could pull a perforated screen membrane back in a platinum box if you have enough water column vacuum. But here's where the problems start. If you're pulling air through the screen surface then dust and other airborne particles will collect around each perforation hole forming little black donuts. In other words, the screen itself will become one huge air filter. I've seen this in the past when uninformed architects have placed HVAC air returns behind perforated screens in auditoriums. Good for screen reorders but bad for screen owner.

Regards,
Don

the .95 gain Screen Research screen was actually brighter at the edges than a flat Stewart 1.3 gain screen.

While I see a few posts from one person that the curved screen "looks cool" I think that the 2.35:1 screens look cool period and don't need a curve to put them in the cool clique.

Hi Mike

When you say brighter do you mean uniformity. A negative gain screen will always have better uniformity. Keep in mind the stewart 1.3 is ISF certified and meets the same standards as the SR.

Im in the camp of a curved screen will always look way cooler then a flat screen because Ive had both and my customers reaction when walking into the room also support this.
The 235:1 ratio really tales advantage of the curve and shows it off.

Flat or curved what ever works for your installation. Im glad to see the 235:1 constant height craze growing. Flat or curved a scope screen is very impressive.

Maybe someday we will get 235:1 anamorphic material to go along with it.
I would like to see Sony offer it in a super bit version. Id be willing to pay a little more for it.

After building over 800 large torus screens for commercial and motion picture exhibitors I would like to make the following comment. Theoretically, you could pull a perforated screen membrane back in a platinum box if you have enough water column vacuum. But here's where the problems start. If you're pulling air through the screen surface then dust and other airborne particles will collect around each perforation hole forming little black donuts. In other words, the screen itself will become one huge air filter. I've seen this in the past when uninformed architects have placed HVAC air returns behind perforated screens in auditoriums. Good for screen reorders but bad for screen owner.

Regards,
Don

Don, thanks for contributing to the thread.

What factors go into determining the best radius? Ananmorphic lens and its pin cushion effect? Screen gain? Other things?

Torus cannot have an acoustically transparent screen due to the vacuum required.

Why not? Most people who have built a Torus state that it requires very little vacuum. The usual response is that they find that they have to much vacuum and have to reduce it.

Eric

Why not? Most people who have built a Torus state that it requires very little vacuum. The usual response is that they find that they have to much vacuum and have to reduce it.

Eric

The holes in an acoustic screen make up for 40% or more of the missing material.
You would need one heck of a fan to keep the tension.

Is here anyone brave enough to give it a try:)

....not to mention the black donuts Don mentioned as the screen becomes an air filter.

We have a curved 2.35:1 in our showroom for anyone wanting to see what its all about. We'll be getting a masking 2.35:1 as soon as someone buys the screen we have. :)

Dennis,

Does a torus/non-perfed screen automatically cause issues or is it more of a potential issue that can be compensated for during the design and construction. I admit one of the first things I noticed when I hung the torus was an echo when I spoke into the screen but it only occured when I was standing directly in front of it. None of my speakers are directed at the screen and during movies I haven't noticed any adverse issues. Thanks.

Gary

The effect can be reduced; but, not eliminated.

Maybe someday we will get 235:1 anamorphic material to go along with it.
I would like to see Sony offer it in a super bit version. Id be willing to pay a little more for it.

the Superbit trademark is owned by Columbia/Tri-Star. All of Sony's pictures that have been sold as Superbit have been under Columbia/Tri-Star label as far as I recall.

I would also like to see 2.35:1 anamorphic titles, but I don't think we will see that anytime soon. I do not believe it is a spec for HD-DVD or BluRay and so we won't see it added later unless they are seperate titles like Laserdisc. Anamorphic LaserDisc never took off and anamorphic DVD wouldn't do well either. Really, how many people have or will have anamorphic lenses and widescreen 1080p projectors to begin with?

...but on a 2.35:1 you don't need top/bottom masking..only side masking.


I have 4-way to take care of Ben-Hur. (I will also use it to mask down for other projectors in the theater, as it is a showroom and will have multiple projectors - some of which cannot light up a 150" wide screen)

I can also run 1.85:1 material fullscreen on the 16x9 panel and use the masking to cover the small bars on the top and bottom if I just slide the anamorphic lens out of the way.

Still, for most people, they wouldn't need 4-way masking on a 2.35:1 screen.

My mistake, I didn't see page two when I replied. I guess one doesn't need a giant air filter.:) I guess this would bring us to which is more important the image or the audio. I know Peter (Cineramax) has gotten me into the mindset of better projected image (especially with a Torus). I noticed this recently when I stayed with my best friend. He has a cheap HTIB with his projector and I didn't feel like I was paying attention to the quality of the audio. I realize it isn't that good, but I guess I was more into the image than the sound.

Eric

After building over 800 large torus screens for commercial and motion picture exhibitors I would like to make the following comment. Theoretically, you could pull a perforated screen membrane back in a platinum box if you have enough water column vacuum. But here's where the problems start. If you're pulling air through the screen surface then dust and other airborne particles will collect around each perforation hole forming little black donuts. In other words, the screen itself will become one huge air filter. I've seen this in the past when uninformed architects have placed HVAC air returns behind perforated screens in auditoriums. Good for screen reorders but bad for screen owner.

Regards,
Don

Nothing like a good installation history to gain knowledge. Thanks!

The effect can be reduced; but, not eliminated.

Thanks Dennis. My wife and I already have a great designer picked out (hint hint) so at least I can minimize the effect until my CRT dies and is replaced with a digital.

After building over 800 large torus screens for commercial and motion picture exhibitors I would like to make the following comment. Theoretically, you could pull a perforated screen membrane back in a platinum box if you have enough water column vacuum. But here's where the problems start. If you're pulling air through the screen surface then dust and other airborne particles will collect around each perforation hole forming little black donuts. In other words, the screen itself will become one huge air filter. I've seen this in the past when uninformed architects have placed HVAC air returns behind perforated screens in auditoriums. Good for screen reorders but bad for screen owner.

Regards,
Don

Don,

Do you still make the high gain white material for the simulation market (Xenon white I think)? Any pieces still laying around? Thanks.

Gary

Don/Dennis: how much can a curved screen compensate for a high gain screen so that it doesn't hot spot? In other words, at what screen gain level will you still see hot spotting with a curved screen? 1.3, 1.5, 2?

I'd expect a curved screen to act like a lens. The objective being to take an angular source (the PJ) and reflect it back out into the room not angled (perpindicular to the wall), no matter where light hits the screen. If that was the case, gain would not matter I would think.

However, if the curvature is not just right then the amount of hotspotting would be proportional to the error of the curvature.

But it's just a hypothesis. No experience.

I'd expect a curved screen to act like a lens. The objective being to take an angular source (the PJ) and reflect it back out into the room not angled (perpindicular to the wall), no matter where light hits the screen. If that was the case, gain would not matter I would think.

However, if the curvature is not just right then the amount of hotspotting would be proportional to the error of the curvature.

But it's just a hypothesis. No experience.

It could be that the higher the gain, the higher the required radius. This is just a guess ofcourse because I have no idea how to determine the right radius. Can anyone help with this question? Thanks.

My understanding is that the curve is to ensure that light reaches all parts of the screen at the same time

The same could be said about the positioning of the LCR speakers in arc, that the time arrival of the sound from each speaker should be the same back to the ears if the baffle of each speaker is positioned to form an arc.

Something that has been missed however is the fact that cinema lenses output light from the centre outwards, where a home theatre projector's light output is based on either the top or the bottom depending on how the unit is mounted and this will affect the out come...

Mark

I don't have a curved screen, and if I did it would be empty because I don't yet have a projector either, but I have been lurking in the constant height forum for a while and would eventually love to have a CH setup. I do however have a very basic understanding of the physics of light and the way a projector works (at least the physical lighting aspects of it.) Feel free to corect me if I'm wrong, actually, please corect me if I'm wrong, but here is what I think.

Just based on what I think the physics of the situation is, I would think that the radius would be the same as the throw distance from the projector. The point being that all the light would then be traveling an equal distance from pj to screen and it would all be hitting the screen at a perpindicular angle. Obviously this is less true with a single axis curve than it is with a torus, but that seems like the basics principal to me. If I am correct about the radius, then the hotspotting should never be a problem. Of course I am talking in a strictly hypothetical situation, and because the projectors have been built to look OK on a flat screen you are dealing with two solutions to one problem which will often add up to a mess. That last part makes me wonder... when you use a curved screen, do you have to do extra processing to make the image square again or can you turn off the processing that the projector has built in?

Just my thoughts and questions,
Brian

Edit:
I think Mark and I are saying roughly the same thing, aparently at the same time too.

Brian:

In most cases, the radius is working out to be about double the throw distance, or slightly more (and, I don't recommend everybody running off and just doing it this way..please). The projector and lens system is designed to provide a non-distorted image on a flat screen with no visible lack of uniformity. The addition of an anamorphic lens (deliberate distortion of the image) can add a pincushion effect...this effect is eliminated along the horizontal axis with screen curvature. Beneficial side effects of the curvature include: (1) more of the reflected light is directed into the seating locations (where it is useful) and less onto the walls; (2) this brings more uniformity of the image into the seating locations; and, less hotspotting when higher gain screen materials are used.

The radical curvature you suggest would work for a single seating location which would happen to be at the projector lens. We're dealing with a larger seating area where picture uniformity is desired. We don't want viewers at the left and right extremes of the seating area to have a distorted image either.

Brian:

The radical curvature you suggest would work for a single seating location which would happen to be at the projector lens.

Yes. Why not just look directly into the projector for that truely widescreen experience. (DO NOT ATTEMPT THIS YOU'LL BURN YOUR RETINA OUT AND THEN BE SATISFIED WATCHING A DLP!)

"The projector and lens system is designed to provide a non-distorted image on a flat screen with no visible lack of uniformity. The addition of an anamorphic lens (deliberate distortion of the image) can add a pincushion effect...this effect is eliminated along the axis with screen curvature."

Does this happen due to the fact that cinema lenses disperse light uniformly from the centre and HT projectors work from one plane, either the bottom to top (shelf mounted) or top to bottom (ceiling mounted)?

During my research, a cinema installer informed me that I would have to bow my screen when using a domestic display device instead of a commercial one...

Mark

My understanding is that the curve is to ensure that light reaches all parts of the screen at the same time.

Mark, you have to be kidding, right? Light travels 186,000 miles per second. How much of a time difference is 6" going to provide? I seriously doubt you can even find much in the way of equipment that could measure such a small difference in time.

Dennis,

Thank you for the clairification. You are a fountain of knowledge.

Thanks,
Brian

BTW, if you're using a Screen Research screen, take a piece of 1" fiberglass, cut to the outside size of the speaker, cut cutouts for each of the drivers and install on the face of each speaker.

Dennis, whats the best way to attach the fiberglass to the cabinet? Put screws through the fiberglass and attach to the front grill clip holes?

Tukkis:
I use black electrical tape all the way around the cabinet on the top and the bottom just to keep it in place (and not damage the speaker cabinet for a future eBay sale).

Tukkis:
I use black electrical tape all the way around the cabinet on the top and the bottom just to keep it in place (and not damage the speaker cabinet for a future eBay sale).

Thats sounds like the best option.

Sorry to hijack the thread, but for mounting speakers behind the screen, is it recommended to treat the screen wall?

Also for mounting the front three speakers. On stands? Hang off screen wall? On some sort of platform?

Thanks

Either the wall behind the speakers (and side walls) need to be treated, or you need to baffle mount the front speakers. Stands will provide the most flexibility.

Thanks Dennis.

One final question: Is the best height for the speakers behind the screen dead middle? So the center speaker is in the middle point of the screen?

In a commercial theater, the HF horns are generally placed 1/3 of the way from the bottom edge of the screen.

In an HT, I would expect that placing the tweeters on the level of ones ears when seated in the back row would be best.

Vern

If the screen is positioned correctly, the speaker's tweeters end up on the screen center line.

Because the implication is that the correct screen position has the vertical center of the screen at the same distance from the floor as your eyes/ears when you are seated in your chair, correct? Or are you recommending that the tweeters fire over the top of your head?

I ask because in a "real" movie theater, from a seat one-third back, you would be sitting substantially lower in relation to the screen's height.

Because the implication is that the correct screen position has the vertical center of the screen at the same distance from the floor as your eyes/ears when you are seated in your chair, correct? Or are you recommending that the tweeters fire over the top of your head?

I ask because in a "real" movie theater, from a seat one-third back, you would be sitting substantially lower in relation to the screen's height.

In HT, one would aim to have both the eye line to centre of the screen and ear height to the tweeters to be the same. This might require the speakers to be tilted up and or the installation of risers to elevate the seating.

Even speakers with Controlled Vertical Directivity can be set up so that the sound covers most seating positions as the sound dispersion becomes wider the further away from the speaker one sits.

In a well designed commercial cinema, one third back should now have you centre of the screen thanks to "stadium" seating. Just my $0.02 worth...

Mark

Does a curved screen have any impact on Moire, good or bad, if you use a perfed screen? Does it depend on size? If so, assume a 10' wide scope screen

The correct screen position would have the primary seat 12 degrees below screen center and the top no more the 30 degrees above eye level for any seat.

Once you have an anamorphic lens, you won't have moire.

[Once you have an anamorphic lens, you won't have moire.[/QUOTE]

What about when you're bypassing/removing it because you're watching 1.78 material?

I've spec'd out the appropriate radius, frame and screen gain needed in my situation with Don Stewart's help and DE's encouragement and am just waiting for the quote. The width of the screen will be 123" (scope). I've decided to not perf the screen and it will get a 1.5 gain. Be sure to check out the different frame options if you ever decide to do this.

I found this link interesting because it gave a simple yet convincing argument in favour of curved screens

http://www.mdicinema.com/en/tools/gain_and_curved_screens.htm

The correct screen position would have the primary seat 12 degrees below screen center and the top no more the 30 degrees above eye level for any seat.


So 24 degrees from eye level to top of screen? Seems alot of Home Theatre?

If I understand Dennis' comment, he is saying that for the money seat, the center of the screen is 12 degrees above seated eye level. That jives with my rule of thumb I have used in the past to install the screen so that MFVs eyes are 1/3 to 1/2 screen height from the bottom of the screen. (See the next post, now I think it might not jive with my previous experience) IOW, when you are seated in the best seat, your eyes should be between 16" and 24" up from the bottom of a 48" tall screen. That way, your neck isn't straining looking up too much and you still have a nice cinematic feel.

The second part about 30 degrees means that no seated viewer (even if the primary seat isn't in the front row) should have to look up more than 30 degrees from horizontal to see the top of the screen. I agree that is a lot. It makes sense for that to be a worst case scenario, not necessarily a recommended vertical viewing angle.

Dennis,
I have been doing some cipherin', and the 12 degree subtended angle seems extreme to me. Staying with my example of the 48" tall screen, that would put eye level 3.9" below the bottom of the image. Am I misunderstanding your post? Is my math incorrect? I was just using (tan12degrees)*(viewing distance)=vertical displacement. This gives approximately 27.9" of elevation from eye level to the center of the screen for what you have described as the primary seat. What am I missing?

Also, with a constant height setup, and assuming the ideal 36 degree HVA for 16:9, this makes the max vertical angle from the primary seat work out to 21.58 degrees. ArcTan(51.9/131.25)=21.575 degrees, so that's well inside the 30 degree worst case scenario.

I am just trying to understand the combination of "ideal 12 degree subtended vertical angle" with the idea of having eye level between the middle and bottom of the screen height. Unless I made a mistake, it appears the two are mutually exclusive and contradictory goals.

I'm even more confused now.

Seems anywhere between 10-20degrees seems comfortable.

The second part about 30 degrees means that no seated viewer (even if the primary seat isn't in the front row) should have to look up more than 30 degrees from horizontal to see the top of the screen. I agree that is a lot. It makes sense for that to be a worst case scenario, not necessarily a recommended vertical viewing angle.

I read somewhere (some SMPTE guidelines or maybe on the THX website?) that in a real cinema the worst case scenario is 45 degrees from the front row to the top of the screen.

That's a bit extreme if its right, but as we would not have more than 3 row in a HT, 30 degree from the front row might still be be OK with less being preferred...

Mark

CAVX,
With a 45 degree angle from the front (worst) seat, you don't even have to do math to realize that this means the vertical distance from the top of the screen to eye level is EQUAL to the horizontal viewing distance. Sitting 15 feet away means having the top of screen 15 feet over your head! Talk about a neck-strainer! That is definitely one of the theater guidelines that is only appropriate for commercial cinemas. :)

The 21.58 degree viewing angle to top of screen I posted above is based on the "ideal" 12 degrees posted earlier. If the primary seat were in the second row, then the theoretical 30 degree worst case could only happen for someone in the front row anyway. We could calculate the front row spacing based on my example if you would like, just for kicks!

Tukkis,
I am trying to rationalize the info, as well. Dennis is a respected designer, and that is why I would like him to clarify the statement he made about the ideal 12 degree elevation. The statement seems obvious and simple, but when you calculate the results, it would put the ideal eye level below the bottom of the screen. This is not just for my example; understand that the geometry would make this true for ALL screen sizes. It just doesn't go with my intuitive thoughts on the subject, which as I mentioned are keeping the viewers eye level between 1/3 and 1/2 of screen height. I would like clarification for my own understanding, and so I can correct my process in case I have been doing it wrong all these years. I really am trying to better myself.

CAVX,
With a 45 degree angle from the front (worst) seat, you don't even have to do math to realize that this means the vertical distance from the top of the screen to eye level is EQUAL to the horizontal viewing distance. Sitting 15 feet away means having the top of screen 15 feet over your head! Talk about a neck-strainer! That is definitely one of the theater guidelines that is only appropriate for commercial cinemas. :)

The 21.58 degree viewing angle to top of screen I posted above is based on the "ideal" 12 degrees posted earlier. If the primary seat were in the second row, then the theoretical 30 degree worst case could only happen for someone in the front row anyway. We could calculate the front row spacing based on my example if you would like, just for kicks!

EDIT: I am NOT dis-agreeing with that, but we have cinemas here that have front row seats that lay right back. Not where I want to sit...

Mark

I am not clear on what you're disagreeing with.

Here are two questions that I've got while considering to curve or not to curve.

Here's a scenario. You're in CH heaven with a projector, anamorphic lens, and curved screen. The curvature of the screen is perfect, the image is the same height everywhere. Time passes and you're going to replace the projector with a different model. Either you can't find/fix the exact same model or you're upgrading.

Do you need to find a projector with the exact same lens attributes (focal, zoom, throw) in order to not have to change the radius of the screen? IE, does the projector's lens figure into the radius calculation of the screen?

I think the answer's "yes." For those of you who have had curved screens and swapped projectors, what do you do? Have another screen frame made? How hard is it to match the old lens? Is this even a problem? I figure if ya went through the pain to get it perfect the first time you're going to want it perfect the next time too.

It has been stated many times that a curved screen sends more light back to the seats. Since this is essentially increasing the gain of the screen, is there a formula or rule of thumb for figuring the new screen gain?

Thanks much....
--TVDinner

It also makes it difficult for masking systems and impossible for 4-way masking systems.


4-way motorized masking for a screen curved in one dimension would be easy. The curved mask edge needs to be made from solid material. Options for the rest of the panel:

1. The entire panel is solid. Disadvantage: The screen border needs to be wide enough to conceal the masking panel, although on a 16:9 screen you want to mask down to 2.40 the top and bottom masks are only 13% of the total screen height. Advantages: The mask curve exactly matches the screen curve.

2. A single roll of fabric is used for the rest. Disadvantage: the screen is surrounded by a shadow box that forms a chord across the curve.

3. Multiple overlapping rolls of fabric forming a polygon are used for the rest. Disadvantages: mechanically connecting the rollers would be complex and individual motors expensive.

Sorry if this has been answered elsewhere(could not find it), or anyone has a problem with me asking..;

What is the pricing of the Cinecurve screens (at least a rough number?)

I would be looking at approx 10ft wide (if I can afford it :))

The best answer I got might as well have been: "if you have to ask, you don't want to know" :D:D. But, I think the price I got on a 10' cinecurve was about $16-17 K.

The best answer I got might as well have been: "if you have to ask, you don't want to know"

Thanks GetGray - yes I thought that myself when writing the post :-D

On a good note, I would think since Stewart thinks this will be a 20% of total screen market in a few years, prices may come down.

I guess it can be a long term plan - have to start "a bit" cheaper myself :)

I need to price one of their "regualr" curved screens. Aparantly D. Erskine has been installing them for a while, but I've never seen one. I can find a way to mask it myself for $10K :)

Mark, you have to be kidding, right? Light travels 186,000 miles per second. How much of a time difference is 6" going to provide? I seriously doubt you can even find much in the way of equipment that could measure such a small difference in time.


the scatter of the light makes it travel at 126,000 miles per second... the 186,000 you talk about us in a vaccuum tube in a controlled enviroment and not from a projector

Tukkis,
I am trying to rationalize the info, as well. Dennis is a respected designer, and that is why I would like him to clarify the statement he made about the ideal 12 degree elevation. The statement seems obvious and simple, but when you calculate the results, it would put the ideal eye level below the bottom of the screen. This is not just for my example; understand that the geometry would make this true for ALL screen sizes. It just doesn't go with my intuitive thoughts on the subject, which as I mentioned are keeping the viewers eye level between 1/3 and 1/2 of screen height. I would like clarification for my own understanding, and so I can correct my process in case I have been doing it wrong all these years. I really am trying to better myself.


I actually went and checked out D.'s showroom, and to be honest...I was a little taken back by the vertical location of the screen. I can confirm the bottom of the screen was ABOVE my eye height. Now I am not a tall person (5'7"), so perhaps this was "high" due to my height. However, I must say I am VERY acustomed to sitting at 1/3-1/2 screen height when going to a theater and this location would take some getting used to for me.

I am not clear on what you're disagreeing with.

I hate when I leave the word NOT out...

Mark

We have a curved 2.35:1 in our showroom for anyone wanting to see what its all about. We'll be getting a masking 2.35:1 as soon as someone buys the screen we have. :)


Taking any bids on that screen? :p

sorry to revive an old thread...
Just curious if everyone using a curved screen is leaving the lens in place when viewing 16x9 material. I suppose you would have to since taking the lens out would stretch the top and bottom of the image off the screen at the center doing this.

It appears I don't need a curved screen if my throw for the 16x9 image (before an HE stretch) is near 2.4x width. Anyone know if I would get any image distortion with a Prismasonic using the max throw on a BenQ 8720 which is 2.4x ? I'm thinking I have no reason to go curved... just double checking.

thanks in advance,
-Bert

I can confirm the bottom of the screen was ABOVE my eye height.

No it isn't. But it is close. Also note, the backs of the chairs are not perpendicular to the floor (in their raised position). Thus, your normal sitting position has your eyes aimed directly at the 1/4th to 1/3rd height position of the screen.

Taking any bids on that screen?
It has been sold. Sorry.

Bert...if your concern is $$$ get a flat screen. If your concern is video quality, curve it.

http://www.stewartfilmscreen.com/engineering_specifications/CurvedScreens.pdf

thx for the note Dennis,

I'm fine with a curved screen, BUT how would I deal with a curved screen when viewing 16x9 on it? when the lens is not in place the image on top & bottom would go off the screen since it's not flat!? I don't want to leave the HE lens in place for 16x9.

I only want to curve if my image distorts with pincussion/barrel distortion/CA, etc. using a flat 2.35 screen, since using a curved screen does not seem to allow me to remove the anamorphic lens when I want to watch 16x9 material.

Plus if my throw is > 2.4x width, should I expect any image distortion?? if not, curving seems less worthwhile especially cause of the 16x9 viewing issue.

Am I incorrect on this analysis?

Just curious if everyone using a curved screen is leaving the lens in place when viewing 16x9 material.


I am but I am using a HE not a VC. Basically as has been stated, the curvature corrects for barrel caused by the projector/lens combo, so if leaving the lens in place all the time, then yes, it can only benefit the image...

Mark

How would one go about finding the correct radius? I’m contemplating building a curved screen. Thinking about this from a form and function perspective, I’m guessing that the closest viewing position should be the biggest consideration when calculating the curve. It seams to me that the first line viewer has the most to gain, or to lose if careful thought isn’t put into it. For my situation, I have a very small space and would like to go with a wider 2.35 set up, but the two front seats are too close. I’m thinking a curved screen may help in this situation. Is this assumption correct?

You can do this empirically by measuring the distance from the lens to the center of the screen, then measure the distance from the lens to the edge of the screen.
Adjust the curvature so that these distances are the same from any point on the screen.

Don

Actually while logical, it does not produce the effect you desire. Consider for starters that your16:9 image is a perfect square with no curved screen. Note that the high $$ Stewarts are not curved that way. They want to know both throw and lens type to spec their screens. Having seen their designs on paper, I'm positive they do not do it as a radius to the lens.

The only way to do it properly is use the lens. Put it in front of the PJ and measure the points on the left and right where the image is correct and work from there. Someone documented that procedure here somewhere.

There's a formula in this forum somewhere. Do a search and you're bound to find it. It's not as simple as Don states. You have to measure the pincushion distortion to figure it out (distance of squish at the edges of the screen).

It seems curve is expressed in inches from many. For instance, if a string is drawn between each edge, the distance between the string and the center of the screen is x".

It does seem that the amount of radius, even on a large one like Dennis' or at the cinema, is rather mild.

Dennis, is your screen an AT-2?

My current screen is an AT-2. My new screen (enroute) is a CineCurve masking screen. New projector, btw, is a Runco VX22.

How would one go about finding the correct radius? I’m contemplating building a curved screen.If you are using a curved screen to correct for pincushion introduced by an anamorphic lens, the best way to determine the proper curve is to project an image on the wall.

Now, measure the height at the center of the image, then go to either outside edge of the image and, using a tape measure held in a upright position, move it slowly towards the projector until the height of the image projected on the tape measure is the same as the height of the image previously meaured in the center.

Then meaure how far the tape measure is from the wall. This is the amount of rise or depth of curve you will need to correct for the pincushion introduced by the anamorphic lens.

On my 15' wide screen, I needed 8" rise to correct for pincushion.

Vern

I'm sure I'll show my newbieness here, but won't changing the "edge of screen to lens" distance also change the focus at the edge of the screen also?

Vern, how much did 8" rise change the focus? Since that is with an anamorphic lens, did that compensate exactly for the change in focus?

Thanks

how much did 8" rise change the focus?Not perceptably, if at all. However, this is going to depend on the quality of both the prime and anamorphic lenses.

My setup consistes of a Qualia 004 with the medium throw lens and an Isco Cinema DLP 1.5x anamorphic lens.

Vern

Thanks Vern

...and can have a serious adverse impact on room acoustics.


There you go Again. :rolleyes:

It will have serious impact on the room acoustics the shorter the aspect ratio of the screen 1.33, 1.77, or even 2.35 with near floor to ceiling height. It WILL NOT have such adverse effects if designed properly. I have done one Torus room with 1.66 AR screen that is one of the best Music and Film rooms in Fla.

It becomes an acoustical concentrator due to its shape, pointed pretty much right at the prime viewing location. As such it will pick up room reflections and beam them at the viewers location.

Vern

Not necessarily so.

Imagine you are projecting onto your DirecTV satellite dish and sitting where the LNB is.

What Ignorance. In reality only half of actual Torus installs have such effect, the sound concentration part A) Can be designed that whatever minuscule reflections get concentrated into a beam, that this beam is designed to be off axis with the viewer, IE. above their heads.B) If you do not shoot any sound towards the center of the TORUS like avoiding side dipolar speakers you will not hear any sound coming out of it.

By Flanking the screen with some high quality D'appolitto or similar dispersion High Fidelity speakers and mounting the center channel underneath slightly forward, you completely eliminate these conditions that Erskine, Diaz, and Pointdexter are so adamantly admonishing about. They have not seen/heard such installations so any recomendations they are making here is out of pure theory and favoritism of their (in the case of E and P) significantly-inferior-visually approach to ht (the perf screen).

In reality the Torus screen was designed to opticallly match the anamorphic len's pin cushion, & poor corner focus, and to create perfect white field uniformity.

Grant Stewart is extremely excited about the TORUS applicability for 2.35 CIH installs. A single way curve is a horrible bandaid to the anamorphic lens opportunity/problem. It hotspots across the center but leaves the corners and top with little light output.

A properly implemented anamorphic 3dlp TORUS installation is the ultimate high fidelity image in Video nowdays. Gary Reber said so when he saw Star Wars in Cinema DLP. He spoke about image depth and focus, color dynamics and image immediacy. Do not be surprised when you find that some percentage of the Stewart screens shipped in the Future will be TORUSSES.

It is embarassing to read the above narowmindedness in such a progressive forum as this. Ask Don Stewart what movie theaters he goes to when he goes out to the Movies. TORUS movie theaters.

Around this same time next year I shall be putting all this TORUS negativity nonsense to bed, with the CIH system to end all systems.

My current screen is an AT-2. My new screen (enroute) is a CineCurve masking screen. New projector, btw, is a Runco VX22.

That is a nice projector. I like the 55 myself better.

Will you share with us sequential cr with this pj?

When we talk about long throw and not having pin cushion issues with anamorphic lenses what is definition of long throw.

Art

Around 2 to 1.

Thanks !

Art

My current screen is an AT-2. My new screen (enroute) is a CineCurve masking screen. New projector, btw, is a Runco VX22.


Dennis , could you tell us what are the dimension of your curved screen you are getting ( width, height and the throw distance with the VX 22D that you are using)

Throw distance 22', image width 120".

Throw distance 22', image width 120".


Thank you :cool:

Dennis designed my room and specified my curved screen.

Let the experts figure out the particulars of the curved screen.

Warren

hate to interrupt...

anyone know the msrp price of the cine-w non-masking curved screen? I'm hoping no more than 6k to 8k

If I was looking for the 136" 2.35:1 variety....does avs deal these?

We aren't allowed to discuss street prices but FWIW, I've seen quotes on a Stewart 54" tall curved 2.35 non-masking, fixed wall, FH material (not MP) at much less than your range.

This thread is fascinating. It seems to basically say curving the screen can help, but striking the right balance of how much to curve is very difficult.

I rehashed my optics background and having a radius of curviture twice the throw distance should result in the light leaving the screen perpendicular to the wall behind it (at least I think). That should decrease but not completely eliminate hotspotting and should make it so anyone at a given distance should get the same image provided they are within the width of the screen (perfect for a couch). The only way to completely eliminate hotspotting with a high gain screen would be to have the radius of curvature slightly less than the throw and to have the PJ just behind and above your head. Obiviously that isn't practical as there would only be one sweet spot (perfect for a chair).

Practically speaking I would think having the radius of curvature 2 x throw would eliminate hot spotting for all but really high gain (or poorly constructed) screens, and to generalize, l think it's safe to say having a mild curviture of radius as described above for a medium to large sized 2.35:1 screen should create a fairly even/consistent image (in ftL) for a rather large seating area.

That's great, but it hasn't addressed the potential for pincushion effect or barrel distortion. Please correct me if I'm wrong, but I take it as pin cushion effect occurs when a PJ WITH an anamorphic lens casts a widescren image on a large flat 2.35:1 screen. This is especially likely to occur if the throw is less than 2 x the width of the 1.78 portion of the 2.35 screen. The opposite is barrel distortion, and that potentially occurs when a curved screen (particularly when the throw is long) is used WITHOUT an anamoprphic lens in front of the PJ.

So... the question I have is what would be the best combination of throw distance and radius of curvature to minimize the pincushion effect when the anamophic lens is used, minimize the barrel distortion when the anamorphic lens is not used, minimize hotspotting when a moderate to high gain screen is used and maximize the viewing area?

I would imagine that is tough to do, but having the radius of curvature at or a little more than 2 x throw when the throw is a little less than 2 x the width of the 1.78 portion of the 2.35 screen may strike the right balance.

What do you guys think? If you don't think you can make a defintive suggestion, please state the curvature of your screen (flat or curved and if curved what the radius of curvature is), which PJ you use, then length or your throw, which anamorphic lens you use (if you have one) and comment on your experience in your home theater.

This is particulaly important to me because I'm seriously thinking of building a DIY curved 2.35:1 AR screen with a sheet of 1.24 gain white laminate. Total cost should be about $150. Obviously it won't be as good as a curved Stewart screen, but people in the DIY screen subforum seem to like this material a lot, and it would be fun to make. There is a lot of potential, but if it doesn't work, at most I lose $150 and a little bit of time. Not a bad gamble :).

This is particulaly important to me because I'm seriously thinking of building a DIY curved 2.35:1 AR screen with a sheet of 1.24 gain white laminate. Total cost should be about $150. Obviously it won't be as good as a curved Stewart screen, but people in the DIY screen subforum seem to like this material a lot, and it would be fun to make. There is a lot of potential, but if it doesn't work, at most I lose $150 and a little bit of time. Not a bad gamble :).

I'm planning the same thing, a 136" 2.35:1 (or 2.40:1 perhaps) using Wilsonart laminate (haven't picked my projector yet, so not sure whether Designer White or Platinum / Fashion Gray). Also planning on curving it - I'll likely just measure / eyeball it, using the info from this thread and others as a starting point. I'm several months away from hanging a screen though.

Good... two people in the same boat!

I'll likely get the PJ (most likey Sanyo PLV-Z5), some Designer White laminate, throw it on the wall and see what happens. If it's distorted or hotspotting occurs, then I'll just play around with some curves and go from there. At that point it's only wood that's being wasted :). Since the Z5 isn't all that bright I don't think hotspotting will be much of an issue.

Still, it would be nice to get opinions from people who have already tried it.

the question I have is what would be the best combination of throw distance and radius of curvature to minimize the pincushion effect when the anamophic lens is used, minimize the barrel distortion when the anamorphic lens is not used, minimize hotspotting when a moderate to high gain screen is used and maximize the viewing area?

Anybody... Please!

If you don't think you can make a defintive suggestion, please state the curvature of your screen (flat or curved and if curved what the radius of curvature is), which PJ you use, then length or your throw, which anamorphic lens you use (if you have one) and comment on your experience in your home theater.

I know a lot you have curved screens... please tell us about your screen, especially what works and doesn't work!

I would say that calculating the curve with combination of Lense & no lense would be halfway inbetween...

ie completly flat surface is perfect for a projector without anamorphic lense, and based on what your projector image curve actually makes with the lense system as the maximum curve. ( can be calculated, but I measured with the 'stick method' )
so for me:

projector: panasonic ae700
lense: DIY anamorphic set for 2.35:!
screen: DIY curved PVC/foam gain of around 1.2

initially I put the lense up and setup as correctly as I could, and gave me an equal curve horizontally top and bottom.
Used a long pole that reached vertically from the ground to above the top of the projected image and marked the top and bottom of the image on the stick at the center (horizontaly) of the image. I then moved the stick to the Left hand edge of the image and moved the stick towards the projector until the marks lined up with the image. Then I measured the distance to the wall, this gave me the "rise".
from that you can calculate the radius ( for me it was around 9.4 meters I think) , but doesn't matter as I can calculate the circle from the width of image I want and the 100mm rise from the L & R edges.

you can calculate the radius from the Width of screen and rise with:

screen curvature radius = r
Screen width = w
screen rise = sr

r=( (w/2)^2 + sr^2) / (2 * sr )

And with that formula you can calculate any point on the curve.
see this post for the worksheet that Mark.J.Foster kindly worked out.
http://www.avsforum.com/avs-vb/showthread.php?t=586590


for me thats in cm:

R = ((274/2)^2 + 10^2) / (2 * 10 )
R = ((18436 + 100) / (20 )
R = 926.8cm

So if you want optimal for both, then that iwll be half of the curve, so make it 50mm rise on each side of the screen, to get an average of the 2.

but for me I'm going to leave lense in place and compress the image for 16:9, as you allways have to have some loss somewhere at difference aspects, but minimal because I'll be mostly viewing dvd's, and sometimes Hidef dvb sports channel occasionally.

So really you need to look at your usage...

>%50 in 1.76 format then keep it flat and remove lense when not needed, and have a good masking when you do
50/50 1.76/2.35 then maybe half the rise for your curved screen and good masking
>%50 in 2.35 format then use mostly lense and 2.35 full rise for your curve, and remove lense with good masking, or use the compress image to 4:3 for less quality 1.76 format (loose %30 horizontal pixels)

Thats my take on that.

Hi

Going 2.35 using a SIM2 HT300Plus, sitting at about 11' , do I really need a curved screen (Stewart, Firehawk, acoustic transparent) ? The hoizontal is 81" only

The other advantage I see is the room is not completely black (white ceiling and walls) so maybe the curved screen can help ?

thanks
pyro:confused:

Newbie trying to clarify some information.

Considering JVC RS25, 95 to 108" Wide CineW 1.3, prismasonic HD5000R, low ambient light

1. I understand the curved screen is supposed to increase the viewing cone. Am I correct in thinking that viewing will still be good if my outer seats are outside the width of the screen, or do I need to place my seats within the width of the screen?

2. I have some additional width and was going to place my R/L speakers to the side of the screen. Considering what I am reading, am I crazy for not maximizing my screen and going acoustically perforated. I am very interested in a high quality picture that will view well when there is low ambient light and audio quality for music listening.

was told if the throw ration is closer than 1.6 (divide lens to screen by screen width desired), then the anamorphic lens will need to correct for pin-cushioning effect. So for my case for if doing 2.35 (which I have decided not to), the throw is 1.39 so i need it

Anybody... Please!



I know a lot you have curved screens... please tell us about your screen, especially what works and doesn't work!

The exact curve is TR and A-Lens dependant. The name I know this as is called 'ray tracing' and whilst it sounds complex, it is not rocket science and you can do this yourself. The easiest way to do this is to use a stick on a stand that is tall than your screen.

Vern describes the process earlier, here is my version.

1. If the screen is mounted to the wall, then place the stick in the centre of the screen as close to the surface of the screen as possible whilst projecting through the lens onto the screen.
2. Mark the image height on the stick- IE the top and bottom of the beam from the projected image.
3. Move the stick to one end of the screen and you will notice that the beam now extends beyond the original height.
4. Move the stick out from the wall to the point where the beam is now the same size as the orignal markings.
5. Measure this distance back to the wall. This is now a representation of how far the ends of the screen need to come out. Both ends should be the same if the lens is set up correctly.

If you can make your screen to curve to match the measurments you've taken, your image will be perfectly framed and you will have elimated pincushion caused the anamorphic lens.

My screen was orignally flat, and I have curved it using a custom rig. You can read about it HERE (http://cavx.blogspot.com/2007/01/going-at.html).

That's the way I did it. The result will be a perfect curve for your installation to compensate for pincushion.

Vern

That's the way I did it. The result will be a perfect curve for your installation to compensate for pincushion.

Vern

My screen is thread adjustable meaning I can customize both the top and bottom (if need be) to perfectly match. May I ask what you used for framing to hold your screen in shape?

1x2's. Simple, light, and cheap.

Customizable corners wouldn't work for me because the masking and curtain tracks have a fixed curve.

Vern