Update: Projection Screens
Everything old is new again for those who forget the past and why we found it necessary to dump curved screens in the first place. They're back! Even more frightening is silver screens have made a brief appearance for 3-D images. The silver surface was said to be necessary to preserve the different polarizations of the left and right eye images. Da-Lite has proven that is no longer the case.
We dropped out of supporting video projectors, with their requirement of curved screens. Along came the Sony 1270 being shown on flat screens. Granted the screen gain was 2 or more, but they were flat screens. JKP determined if you could deal with a smaller image, we could reduce the gain to 1.3 and produce a far better image than anyone ever thought possible from a video projector. If you wanted a brighter image, just add another projector.
Curved screens made a come back in someone's quest to make 2.35:1 letterboxed images fill the screen. The 2.35:1 letterboxed image is stretched vertically to fit the 1.78 aspect ratio of many solid-state projectors. It is then stretched horizontally back to 2.35:1 using an anamorphic lens in front of the projector's lens. The original solution was not to fix the lens, but to curve the screen to compensate for the focus errors. It became a fixed solution for a variable problem. It also became a 'new' trend for those who forgot that we did away with curved screens in the first place.
Again, what we are seeing is significant distortion in image geometry, and unlike the analog days of CRT displays, they aren't easily fixed in solid-state projectors. The curved screen only helped the lens-focus problem but did not fix it. The irony of adding the lens in front of the projector is that it killed the focus capability of the projector. On a 10-foot-wide image, the depth of focus on my projector is at least two feet. The additional lenses drop that focus to less than zero and the outside edges of the image on a flat screen went out of focus. The screen had to be curved to keep the edges of the image in focus. The curved screen was then being sold in applications where it wasn't needed. It was the 'new' trend. Even leaving out the geometry distortion added to the image, there is the audio distortion of the curved screen added to the room acoustics.