What's the difference between different types of 3D glasses (IMAX, RealD etc)?

[DaMegaTaco]

About to see the new Dr Strange in imax laser 3D and noticed these glasses seem to be pretty different from regular 3D glasses where it looks like it uses blue and yellow lenses. I want to take a pair home, but they seem to have an anti theft and I'm not trying to risk it going off even though I doubt they have the anti theft system installed. So am I right to assume these wouldn't work on my passive 3ad monitor l? Also how do they work? Has anyone else used them?




Edit: The movie just finished... The stuff on the screen didn't look any fifteenth from other 3D even though one lender is clearly blue and the other yellow, which I'm really not sure why. Any explanations would really help!

Edit 2: They definitely had the theft prevention sensors installed and made a lot of effort to make sure the glasses aren't taken. Really wish that wasn't the case as I'm really curious what the difference was between them and the regular dolby 3d was

Edit 3: I just realized it's not real d3D and dolby 3D, which I was able to look up and see the difference so I guess I figured out my answer

[Lee A Stewart]

Dolby 3D

https://en.wikipedia.org/wiki/Dolby_3D

They would not work on your 3D TV which uses cheap polarized glasses

[globalimages2]

I was gonna reply to this, but ended up copying pasting parts of another talk and sticking the reply in the middle. Moderator feel free to edit this, make it its own topic or pin it if you feel appropriate etc.

Basically the 5 most used ways to get 3D nowadays are:

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1) Switched Polarized Light:
(RealD, MasterImage and others). The light from the projector is alternatively split "50%" polarized one-direction and 50% polarized "the opposite". This is used by some >95% of 3D theaters. Most people erroneously refer to the this system as "passive polarized". While the glasses used with it are passive, the system itself is a type of "active" meaning the screen "flickers" each image in succession actively.

Advantages:
-Polarizing filters/devices/active-switchers for projectors or glasses can be made very cheaply. Equipment to "flip" (switch) the polarization of light is cheap, good and practical. Light loss can be made reasonable and efficiency can be kept close to the "theoretical limit" of 50% light loss.

Disadvantages:
-Polarizing filters can not be made 100% "perfect", some light is going to pass through the wrong "filter" due to the quantum nature of light and other limits, producing some "ghosting" (crosstalk or double image). Still, can be made >99.5% effective, so good enough, specially for the cost. Movies playback on this system pass through a "contrast reducing" algorithm to try to minimize this "ghosting".

-Screen must preserve polarization, and again, this can not be done 100% perfect in any practical way, but can be done >99.5%, so good enough, but once more a little "ghosting" is unavoidable. So most screens can not be used and materials such as metallic particles ("Silver Screens") must be used, which has advantages and disadvantages.

-Polarized light is direction-dependent by its nature, thus the more you deviate from "looking exactly ahead through your glasses to the exact center of the screen from the exact middle position" the more "ghosting" you will get. Again, this problem is small and reasonable, specially since the systems used for digital projection use circular polarized light as opposed to linear.

-"Flicker" or more technically "temporal disparity", but we'll call it "flicker".
Although people often refers to the widely used system in cinemas as "passive", the truth is that it's an active system exactly as in some home-TV system, but the "flicker" occurs on the projector instead of on the glasses. The projector splits the orientation of the polarization of the light several times per second (currently 144 times, called 144hz or "triple flash", as in 24fps x 3 = 72hz x 2eyes = 144hz) rendering the passive 3D glasses that audience wears practically as a kind-of "shutter glasses", where one eye sees "totally black" for a "split second" while the opposite eye sees the corresponding image. Then the system "switches" and the other eye gets blocked (sees a "black image") and the opposite eye gets its image, albeit at a slightly different time. This cycle repeats, but both eyes never see both images at the same time. This is functionally exactly the same that occurs in the systems used with shutter glasses, usually referred to as "active 3D". This way, one single projector can display a different full resolution image to each eye, but by "flickering" and splitting the spatial resolution (frames-per-second) in half between the eyes. This flicker is minimal as each eye gets a 72hz refresh and the theater is a dark environment anyway and objects outside of the screen are not "flickering" as it happens in other active systems, like the ones using shutter-glasses instead of passive polarized glasses.


***
2) Passive Polarized Light:
Two images are presented on the screen at the same time, each with the light polarized in a different direction which can then be later selectively blocked by the reciprocal filter in 3D glasses. This 3D system, the one most commonly used in non-digital cinemas until the year 2005, is almost never currently used in theaters installations, as only Sony used it in their cinema digital projector and otherwise would often require two projectors with passive polarizing filters installed on them. Only a handful of theater installations world wide use it today. It's most notably used by many LG-brand passive TV sets.

Advantages:
-No "flicker" as both images are presented at the same time.

-Cost of filters or glasses is minimum.

-Can provide a full resolution image, both spatially and temporally. I.e. two projectors can display their full resolution and their full "frames per second" without having to split either between the left-eye and right-eye views. When using a single TV or projector the resolution must of course be split between each eye.

-Can be light efficient compared to other systems. Using two projectors means using "twice the light" from their two lamps and also the 50%-theoretical-limit of the light that each polarizing filter blocks can be rotated and re-used on each view. Also not needing an active polarization switcher nor a "blanking period" to allow for the polarization state to change improves light efficiency compared to other systems further.

-Easier to get lower crosstalk (less ghosting) than polarization switching systems.


Disadvantages:
-Potentially "twice the cost". Either two projectors, with two lamps and twice the electrical consumption, or in the case of a television set, "twice the pixels" would be necessary for such a system. Thus when used in TV screen, half the available resolution per eye is obtainable.

-Same as with any polarized system, the physics limitations of polarized light: some direction dependency, some small unavoidable crosstalk (ghosting), polarization preserving special screen (silver), light loss, etc

***
3) Light Frequency Separation:
(Dolby/Infitec, Technicolor, others). The light from the projector is alternatively split into narrow frequency bands that can be blocked by the reciprocal filter on the glasses. Choosing two sets of 3 narrow bands of "red", "green" and "blue" light can produce two sets of almost full color RGB images that are separate enough to be filtered out.

Advantages:
-There is no intrinsic physics (i.e. quantum) limitation to the filtering capability, so ghosting can be theoretical zero.

-No need to preserve polarization state, so any screen material can be used, doesn't have to be metallic, so "better" materials can used in more practical ways i.e. viewing the screen from an angle to the side, which would be a problem for polarized light.

Disadvantages:
-For a "natural" light source (i.e. Xenon lamps used by most projectors) the light loss from the filtering is horrendous. Far from the "theoretical" 50% light loss limit, these systems are lucky to EVER get under 85% of light loss.

-The manufacturing and physics of the multiband notch frequency filters for the glasses is at a whole different level than polarized filters, currently requiring multiple materials and steps and restrictions, like with current dichroic manufacturing methods ideally the filters for the glasses would have to be curved and close to the eyes and small in size and would be very prone to reflections from everywhere (i.e. you can "see" a reflection of your own eyes from the light entering the glasses or from the sides of the glasses reflected "back" to your own eyes). So in short: ugly and expensive 3D glasses that suck a lot of light.

-The two sets of RGB color bands would not produce the exact same color on each eye, thus ideally a film should color-correct each view with this system in mind or a little color-remapping could be done on-the-fly during projection. Not too bad, the brain gets used to it fast and produces a good over-all single full color image at the end.

-This system can be used passively with two projectors, thus almost doubling the cost, or "actively" by driving a color filter wheel in the light path of a single projector, which is the usual way it is done (outside Imax installations) or by having a light illumination system switch from two sets of different wavelength RGB lasers. When done "actively", it suffers the same "temporal disparities", which we are calling "flicker" here, as the switched polarized method, where the glasses, although they are passive themselves, actually act as a sort-of shutter glasses "flickering" at 72hz-per-eye with respect to what's shown on the screen, and where each eye sees an image but at a different point in time from the other eye, just like in the equivalent switched polarized system or the shutter glasses systems, but this way a single projector can offer a full (spatial) resolution for each view.

Dolby stopped manufacturing and selling their 3D system to movie theaters many years ago, they were never over 5% of the 3D cinema market, consisting on a kit to install a spinning disc inside the projector with two alternating 3-band interfering filters BUT with the upcoming of laser illumination projectors in the past few years the system is coming back, as the laser light, when done "right", is by its own nature "narrow band" compared to lamp-based projectors (xenon bulb) and thus a "perfect" match for such a system without incurring in the huge light losses it did before, for which the polarized system faired much better in spite of most installation still losing over 85% of the overall light at the end (compared to 2D). At least it was not the 92% overall light loss of Dolby 3D in some cases, easily twice as bad as polarized.

So with the "right" kind of laser projector (6 different laser sources, known as "6P", so two sets of RGB lasers), the narrow-band glasses can match the screen with little light loss compared to 2D.

But laser light is also good for polarized projection, as laser is by nature not only narrow-band but also polarized, thus avoiding some original light loss "if done right". So polarized laser projection continues to be the cheaper alternative, substituting the "one time cost" of using a metallic screen for the much cheaper and practical passive polarized glasses, which can be easily bought in bulk for under <$0.40, while interfering or multichroic 3D glasses for systems such as Dolby will most likely never be sold under $6, currently well over >$15.

https://professional.dolby.com/produ...by-3d-bundles/

https://studio3d.com/omega3d/


***
4) Shutter Glasses:
In this system, often called "active", battery-powered glasses turn one lens "black" while the other remains transparent in quick succession. A few digital theaters used it for a while, but nowadays is mostly used by home theater projectors and some 3D TV's.

Advantages:
-If done right, crosstalk ("ghosting") can be lower than some other methods. Current use of LCD materials and polarized light in the shutters again makes it impossible for the system to be 100% crosstalk free due to quantum physics limits, but >99.98% is achievable, so good enough.

-Like with the narrow-band systems, no need to use a special screen.

-Can perform well at almost any viewing angle (little to none direction-dependency).

Disadvantages:
-Light efficiency is by default limited to a maximum theoretical of 50%, as one eye must block ALL light while the other sees the image. Current LCD based shutter glasses also use polarization to control the shutter, thus another additional 50% of light is loss is unavoidable (75% total minimum light loss), while in theater systems, this other 50% of the light can be switched directions and be re-utilized for the same view. Thus this system will always be a theoretical twice worse light performing than good theoretical passive or polarization switching methods. In practice it's only about 15% worse than the better competing systems.

-Flicker. Everything that's looked through the 3D glasses will "flicker", not only the screen as with the "Polarization Switching Method", but also the surrounding space. Flicker could be made reasonable as frequencies of 144hz and above are achievable, but most current implementations actually use 120hz (60hz per eye, which is noticeable and bother some people, in spite of "marketing" claims of >144hz). Also, it's uncomfortable to look at many light sources through the shutter glasses when they are active, as most LED light bulbs and fluorescent fixtures etc they all "flicker" at their own rate and thus will produce a weird more noticeable "out-of-phase" flicker.

-Glasses' cost/size/batteries. Need I say more. Will always be somewhat worse than some other methods.

-Non standardized method of synching the glasses and the images. Different manufacturers choose different methods to signal the glasses when they must switch the state from blocking one eye to blocking the other in synch with switching to displaying the image from one eye to the other. Thus all kinds of incompatible shutter glasses exists which only work with some devices (TV's or projectors). Common ways to synch the glasses to the devices are: infrared signals (IR), radio signals (RF), standardized radio frequency protocols (bluetooth RHD3D) and standardized "flash" light pulses (DLP-link). They each have potential advantages and disadvantages but the worse thing about it is that many glasses don't work with many systems and when they do they might not be optimized or even be fully compatible with them and offer all kinds of problems or bad performance (i.e. ghosting).

***
5) Anaglyph:
Different right-eye and left-eye images are made in a totally different "single" color and combined in the screen, i.e. complementary red and green, that can be filtered out by "opposite" filters in the glasses.

Advantages:
-Compatible with any system able to reproduce the colors used, so most anything. No need for special screens, projectors, TV's, disc players, printers, etc. Most anything works.

-Very cheap glasses and simple color filters.

Disadvantages:
-Hard/impossible to get good color reproduction on the image since it's been looked through two color filters.

-Hard for the brain to fuse two images with such two difference in colors. This often produces a "double image" which may be confused with "ghosting" which, while also possible and usual with anaglyph systems, true "ghosting" (crosstalk) is NOT unavoidable in anaglyphic systems as a "perfect cancelling" color filter and light source/image density combination and image pair is not physically impossible. But call it "ghosting", which is when one of the eyes sees a little bit of the "wrong eye" image, thus a double image, or call it "unfuseable images", in which although each eye is seeing the correct image and there is no "real ghosting" present at all, the end result is the same: the brain sees "a double image" instead of a single 3D one, so most people just call both totally-different things "ghosting".

There are other methods to "watch some sort of 3D" such as lenticular screens/TV's (mostly marketed as "lightfield displays"), more true lightfield displays, holograms, etc, but those will never be a reasonable substitution for glasses-based systems for stereoscopic (current) 3D films. In the future, other types of films could be made (holographic, lightfield, multiscopic, etc) and perhaps used on those types of display in a practical way.

The upcoming better way to watch 3D in the near future is Virtual Reality (VR) or Augmented Reality (AR) or more basic Face Mounted Displays (FMD), which I guess we can name as the "6th system" to watch 3D.


***
6) VR/AR/FMD
Two separate screen devices/projectors are placed right in front of your eyes in some sort of goggles or glasses.

Advantages:
-All of them. Absolutely zero ghosting (crosstalk). Maximum brightness: 100% equal compared to 2D. No "flicker": both screens can display the image at the exact same time. Maximum 100% spatial and temporal resolution compared to 2D.

Disadvantages:
-The "glasses" needed to hold the screens in front of your eyes must have some weight and size, as it must contain electronics and batteries (or a cable).

-It's hard and potentially expensive to build the optics needed for such a device in a small size and space, not to mention the cost of two displays. As a result, even by mid-2022 VR "glasses" (goggles) are still bulky and heavy compared to the 3D glasses for other systems. It's hard/expensive to get an image quality as good as current televisions offers (i.e. 4K/8K OLED).

-Could be harder to use for people that already wear glasses or need vision correction.

-Only one person can actually see the images at a time per each device. Theoretically, a single "player" could "broadcast" a movie to multiple devices to "watch a movie together in a family", but we are not really there yet and right now each device needs a way to feed the full bandwidth of the 3D film, or need to use HDMI splitters, etc. Watching a film for a family of four would require to purchase 4 VR devices, i.e., and manufacturing constrains might dictate that small children could need to use a smaller model to adapt to their size, which is more expensive and complex compared to i.e. making children-size polarizing glasses.


So which 3D system is the best? Well, none of them are perfect. In movie theaters, actively switched polarized projection is the norm, with very few Dolby 3D. Look for a theater with laser illumination projection, becoming more common in the past 2 years or so and definitely becoming the norm in the next 5 to 10. Lasers have their own problems and shortcomings but it usually means a much brighter 3D image and slightly less ghosting. Very few installations can offer true-passive and 4K 3D at all, >99% of them world-wide will just be 2K switched-polarized 3D. Try to find one with a silver screen that doesn't suck or is covered with (depolarizing) dust to get lower ghosting and try to sit towards the middle of the auditorium. Premium screens advertised as Imax or Dolby use the same projectors available to everybody else, but tends to use the higher end models or setups and more care is taken with equipment/screens/sound/etc in general. The few true-Dolby 3D in operation could offer a more ghosting-free experience and better viewing angles but darker image, unless combined with laser projection which would probably offer top brightness and ghosting performance. The recent installations labeled "Dolby Theater" use a dual laser projection true-passive color-separation setup and Dolby Atmos sound system, so basically top of the line performance. Imax does the same thing, dual laser color separation 3D with multichannel audio setups, but with some potential disadvantages (they use anamorphic lenses and usually high gain screens which can lead to more artifacts and probably inferior sound mix than Atmos).

The most practical for home viewing would be a passive polarizing TV such as LG's for sure. If made with the very best filter technology available, can be cheap and good enough for most uses. If the batteries and slightly "larger/heavier" and costly glasses in not a problem, a very very good system could be made nowadays with shutter glasses easily and cheaply, like it's being used for home projectors, with near zero ghosting and good performance.

If "zero" ghosting is desired, in the future, whenever true micro-LED displays (not micro-LED *illuminated* displays as marketed now) are made, a system could use narrow-band light from the LED's or from true quantum dots, whenever those become available. The glasses will be a bit wonkier, a bit more expensive but reasonable (say $30), passive (no batteries) and ghosting would be "zero". Dolby was the one pursuing this approach in home Television.

Forget about glasses-free TV's in the way we "think about it" for *current* existing stereoscopic films. This can simply NOT BE PHYSICALLY DONE. Not now, nor "ever". New types of films, shot in new ways, or perhaps full-CGI animated films that can be converted, could in the distant future use some glasses-free 3D "TV" or "cinema experience", but not as a replacement for current 3D TV or current 3D cinema (with glasses), but as something "new and completely different" that requires new movies to be made in a different way and whole different "ecosystems". You will NEVER be able to walk into a store and buy a device similar to a current TV, put it in your living room, pop a current 3D blu-ray in some sort of machine and have the whole family spread in the living room watching the film in a 3D of similar quality as current 3D TV's (with glasses), but without them. Never. It can not be made.

Since this statement usually carries some controversy in forums, let me clarify. I'm not saying that SOME "images/movies" can be watched in SOME conditions in "3D" without glasses. Of course they can. I'm saying a device similar to a TV or a projector will NEVER be for sale that will allow CURRENT stereoscopic films to be watched at similar CURRENT quality levels (without "fake on-the fly views" or other alterations similar to crappy auto-conversions) in a situation similar to CURRENT use of 3D TV and movie projectors (a large-ish group of various people, i.e. children and adults, are spread around in different angles and positions over a living-room or auditorium enjoying the movie at the same time). This is so because of PHYSICS restrictions, not because of TECHNOLOGY, so there will never be a solution, just perhaps an approximation with TONS of technology complexities to approximate the physically impossible task, which basically comes down to shooting through space from a "screen" two different images so the right one always lands on the right eyes of ALL the people in the living room, even if they are on the floor or sitting on the lap of another person behind them, while the left images shoots across the space and always lands on the left eyes of those same large-ish group of people, even if they are laying on the sofa with their head on a pillow or happen to be children with smaller heads, without disturbing the others.

This statement is usually proceeded by postings of talks from James Cameron (which are some 10 years old) or some people pointing to some "glasses-free" 3d Tv's or devices that have come-and-go for the past 70 years, since the first glasses free 3D movie theaters opened to the public in Russia, as well as announcements for some specialty products that will soon come and go as well. Mostly from small companies, like if it was possible to make a good glasses-free 3D display system for home or theaters companies like Sony, LG, Samsung, Panasonic, NEC, Canon, Apple, Microsoft, Intel, etc wouldn't be all over it, or the MIT wouldn't have researched the theoretical solution by now since the last time I visited the Media Lab in the 90's.

Some of those companies do have glasses-free good 3D products FOR PARTICULAR applications and restrictions (i.e. for a single user). Even those companies that have the "right" approach to solving the problem (i.e. eye-tracking) know that it's not practical to track the eyes of more than 3-4 people to shoot 8 views (2 per person) at 24fps in any commercially viable way. Much less an unrestricted number of people in unrestricted positions in front of the display similar to current (3D or 2D) TV's offer. To those people I will all reply the same: we'll talk again in 2 years time. If after 10 years you still have hopes of getting a glasses-free "3D-TV" similar in performance to current ones, then if you want, I'll try to explain in more detail while it still won't happen in yet another 10 years ...

You can "easily" make a particular "glasses free" 3D display for a particular application with particular restrictions and particular "quality levels" for a particular cost and even make a particular "film" (CGI animation generated, really, but then again Avatar is CGI mostly) to "approximate" a glasses free 3D cinema or home TV experience, this has been available for well over 25 years, but this will never translate to what I was talking about. And at a cost and quality far worse than "current" 3D TV's, not to mention mostly unusable for current stereoscopic films. The videos below are 11 years old or older.

http://holografika.com/videos/

https://www.youtube.com/watch?v=NiaInndP1S0 (2011)

[DaMegaTaco]

Thanks for the super informative post... Just thought I'd share a few things in response.

As far as the VR 3D method it might be closer then you'd think if these things are as good as they're made out to be... Although if they couldn't display the picture without voicing the light from behind the lens since the picture seems to be transparent then they wouldn't be that great. https://www.kickstarter.com/projects...ywhere-anytime

Regarding glasses free 3D I actually figured out how to convert 3D movies into a format the Nintendo 3DS could play on 3D, which was not an easy process, but it was interesting none the less. I can definitely understand why glasses free 3D will never be good enough for multiple people as well as it probably would be a pain for even one person. Although it is effective at producing a 3D image when it's viewed properly, but that's not necessarily an easy thing to do especially with such a small screen.

I've been pretty happy with the LG passive monitor I got, but just wish it was bigger. It's definitely really awesome though and works well enough even though pop out effects don't really work that great since it's so small. Although I do think the dual play setup they coined is petty neat and hope I'm able to get a chance to utilize it as some point or another.

Anyways thanks again for the first informative explanation even though I managed to figure it out myself.

[Jlardonio]

Originally Posted by DaMegaTaco

Thanks for the super informative post... Just thought I'd share a few things in response.

As far as the VR 3D method it might be closer then you'd think if these things are as good as they're made out to be... Although if they couldn't display the picture without voicing the light from behind the lens since the picture seems to be transparent then they wouldn't be that great. https://www.kickstarter.com/projects...ywhere-anytime

Regarding glasses free 3D I actually figured out how to convert 3D movies into a format the Nintendo 3DS could play on 3D, which was not an easy process, but it was interesting none the less. I can definitely understand why glasses free 3D will never be good enough for multiple people as well as it probably would be a pain for even one person. Although it is effective at producing a 3D image when it's viewed properly, but that's not necessarily an easy thing to do especially with such a small screen.

I've been pretty happy with the LG passive monitor I got, but just wish it was bigger. It's definitely really awesome though and works well enough even though pop out effects don't really work that great since it's so small. Although I do think the dual play setup they coined is petty neat and hope I'm able to get a chance to utilize it as some point or another.

Anyways thanks again for the first informative explanation even though I managed to figure it out myself.

You're still in time to buy one LG passive 3D TV at a good price if you look hard.

[Lee A Stewart]

Autostereoscopic 3D (no glasses) will be the future. It will handle multiple viewers using computerized AI head tracking. TV panel will be native 8K which will produce 4K 3D. The issue with Auto 3D has always been . . . how do you create a TV that is specifically designed to show 3D - and show 2D without any artifacts. They haven't figured that one out yet.