To curve or not - Page 4

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.


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/eng...vedScreens.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?

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.

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

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

There you go Again.

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.

Not necessarily so.

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.

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

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".

Thank you

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 .

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.

Anybody... Please!



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