The biggest problem is with the version of Real D brand 3D that is sometimes used with Sony projectors. Unlike the other Real D systems that project alternate left eye and right eye frames and use a special filter that electronically switches polarizations, the system in question "stacks" two 2K frames on top of each other within the Sony's 4K image field (which is 4 times the size of a 2K frame). The optics superimpose the two frames on the screen, after passing them through fixed polarizing filters. First of all, it only uses half the image area as the two stacked "sub" frames are in the middle with unused area on each side. Right off the bat that throws away half the light output on a projector that is already weak. (So weak in fact that it's not used at all on larger screens.) Then the light is cut by more than half by the polarizers. Apparently someone thought this was a great idea because both left and right frames are on screen at the same time instead of alternating. But it's so wasteful of light on a projector that can ill afford it. While this system cannot easily be removed and replaced--it takes a technician, I have been assured that regular theatre personnel can in fact remove the polarizing filters for 2D. Whether they do or don't is up to the company policy.
I think in the end you will see the theatres using this system removing it and replacing it with the Real D XL or XLW system which should substantially increase the light output. In case anyone cares, conventional Real D has the projector rapidly interleaving left eye and right eye frames while a filter in front of the lens electronically "flips" between two polarization orientations so the Real D glasses let each eye see only the correct image. The Real D XL and XLW systems work the same way but make use of the light reflected off the back of the filter to augment that which passes through. All of them can be moved out of the way for 2D.
But there are other systems besides Real D and I will now post a summary of what happens in a 3D-equipped theatre when a 2D movie is show. Disclaimer: I do not work on 3D systems but have friends who install this stuff and I have verified this information with them.
First of all just so everyone knows, looking back at the projector and seeing twin beams of light does NOT automatically mean it's a Sony projector with a 3D lens. There are other systems that create two beams of light such as some other versions of Real D and Digital IMAX.
Real D with the simple "Z Screen" in front of the lens: Easily moved out of the way for 2D.
Real D using the XL or XLW optics used for larger screens: This can be removed or slid out of the way for 2D. There is even a device that will move it automatically. However, even if left in place when turned off it decreases brightness just a little.
Real D using the split field lens (only on Sony projectors): Generally requires a technician to remove and replace BUT the polarizing filters can be removed and replaced by theatre staff---if company policy allows it. Removing them increases brightness on 2D shows.
Master Image 3D: This is a spinning filter wheel in front of the lens and will move down out of the way for 2D.
XPand 3D: This system uses LCD shutter glasses so the correct eye sees only the proper frames which the projector is interleaving. 2D presentations project normally and there is no dimming of the 2D picture. There are no filters except the shutter glasses which you won't be wearing for 2D.
Dolby 3D: A small filter wheel inside the digital projector moves out of the way for 2D which then projects normally.
True Film IMAX: 2D shows run on one projector as usual. No change in brightness.
Digital IMAX aka Fake IMAX or LieMAX: This system uses two separate projectors side by side. When running 2D, the polarizing filters move out of the way automatically. Both projectors are still in use for 2D presentations so there will still be twin beams of light.
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I think in the end you will see the theatres using this system removing it and replacing it with the Real D XL or XLW system which should substantially increase the light output. In case anyone cares, conventional Real D has the projector rapidly interleaving left eye and right eye frames while a filter in front of the lens electronically "flips" between two polarization orientations so the Real D glasses let each eye see only the correct image. The Real D XL and XLW systems work the same way but make use of the light reflected off the back of the filter to augment that which passes through. All of them can be moved out of the way for 2D.
But there are other systems besides Real D and I will now post a summary of what happens in a 3D-equipped theatre when a 2D movie is show. Disclaimer: I do not work on 3D systems but have friends who install this stuff and I have verified this information with them.
First of all just so everyone knows, looking back at the projector and seeing twin beams of light does NOT automatically mean it's a Sony projector with a 3D lens. There are other systems that create two beams of light such as some other versions of Real D and Digital IMAX.
Real D with the simple "Z Screen" in front of the lens: Easily moved out of the way for 2D.
Real D using the XL or XLW optics used for larger screens: This can be removed or slid out of the way for 2D. There is even a device that will move it automatically. However, even if left in place when turned off it decreases brightness just a little.
Real D using the split field lens (only on Sony projectors): Generally requires a technician to remove and replace BUT the polarizing filters can be removed and replaced by theatre staff---if company policy allows it. Removing them increases brightness on 2D shows.
Master Image 3D: This is a spinning filter wheel in front of the lens and will move down out of the way for 2D.
XPand 3D: This system uses LCD shutter glasses so the correct eye sees only the proper frames which the projector is interleaving. 2D presentations project normally and there is no dimming of the 2D picture. There are no filters except the shutter glasses which you won't be wearing for 2D.
Dolby 3D: A small filter wheel inside the digital projector moves out of the way for 2D which then projects normally.
True Film IMAX: 2D shows run on one projector as usual. No change in brightness.
Digital IMAX aka Fake IMAX or LieMAX: This system uses two separate projectors side by side. When running 2D, the polarizing filters move out of the way automatically. Both projectors are still in use for 2D presentations so there will still be twin beams of light.
Technicolor Film 3D: The 3D l