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RealD vs. Imax Digital 3D: What’s the difference? | CNET Asia

January 6, 2013

From CNET Asia by Timothy Fernandez on 1/4/13

3D movies are quite common these days, with many of the latest animated films, action-packed blockbusters and horror flicks being presented with a third-dimension. The passive polarizing technology used to display 3D in most movie theaters is also similar to those found in passive 3D TVs. However, the fact that some movies are presented in several 3D formats in the theaters can be somewhat confusing.

Most of us who’ve caught a 3D movie at the cinemas recently probably experienced the more common RealD 3D technology, while Imax Digital 3D (as well as its analog counterpart) is a format presented at Imax auditoriums. But is there any difference between RealD 3D and Imax Digital 3D? Here what we know.

First, the similarities

RealD 3D and Imax Digital 3D both utilize passive 3D technology, which makes use of relatively lightweight eyewear. These passive 3D glasses use polarizing filters to allow each eye to see a slightly different image. This is why the glasses can sometimes seem darker in one eye than the other–it’s meant to block out certain spectrums of light. The glasses at Imax theaters are larger, to compensate for the larger field-of-view at those auditoriums.

Both these technologies are also digital, which means that you’ll get a clean image and none of the image noise or “cigarette burns” that are visible from regular film projectors.

How they compare

RealD 3D

The prevalent technology in 3D cinemas worldwide comes from RealD, an American company founded in 2003. The RealD 3D format is natively digital. This means that movies have to be produced in a digital 3D format for projection on film-less digital projectors. RealD cinemas also use a passive circular polarizing technique to achieve 3D which allows viewers a clear image even when turning or tilting their heads. Passive 3D TVs use circular polarizing technology, too. The first RealD 3D movie screened was Chicken Little in 2005.

Imax Digital 3D

An Imax auditorium in Singapore. (Credit: Shaw Theaters)

This is a competing format that’s been around for a little longer. Imax cinema auditoriums are well known for their massive, curved screens which fill a larger portion of your field-of-vision (FOV), or how much your eyes can see at any one time.

Imax Digital 3D is an evolutionary improvement of the analog Imax 3D theaters that have been around since 1986. Its long history is evident even in the much newer Imax Digital 3D theaters since they still utilize the linear polarizing technology of its analog predecessors. Unlike RealD, Imax 3D movies are less tolerant of head movements. Viewers have to avoid tilting their heads, though some turning–probably unavoidable due to the massive Imax screen format–is possible. Also, Imax screens are curved to fill an audience member’s FOV, which enhances immersion while giving those sitting at the sides a better view of the action. Imax Digital auditoriums also use two 2K projectors for 3D shows, which leads to a visibly brighter image through the glasses.

While many Imax theaters these days are digital, there are still auditoriums with the analog Imax 3D format in the US and some other countries. These auditoriums typically have a larger screen and correspondingly large projection equipment and tend to be used for documentaries instead of feature films, too. Omnimax theaters (recently renamed as Imax Dome) are a variation of this analog format, but have a dome-shaped screen.

Why do Imax Digital 3D movies cost more?

3D ticket prices vary across Asia but Imax Digital 3D tickets typically cost more than their RealD 3D counterparts. In Singapore, a weekday ticket to a new movie at the Lido Cineplex starts at S$19 on Imax Digital 3D while the average cinema with RealD 3D charges S$12 on average. At an AMC cinema in Los Angeles, a typical Imax Digital 3D movie starts at about US$12, while the same movie on RealD 3D would be about US$2 cheaper.

Theater audiences are paying more for Imax 3D movies for a few possible reasons. The first would be the consistent audio and visual quality across Imax auditoriums, the generally larger screen (that’s at a closer proximity to the audience) as well as a brighter image from the dual-projectors.

Of course, certain cinemas that use the RealD format for 3D scrrenings do have other selling points such as sharper 4K projectors, or better sound. An example of the latter would be auditoriums with Dolby Atmos setups, which can present more believable surround sound effects.

Just the facts

Aside from the larger screen size, there are other notable differences between Imax Digital 3D and RealD 3D. RealD 3D projectors like Sony’s 4K Digital Cinema models use a special lens to project 3D visuals which can provide viewers with up to four times the resolution of full-HD 1080p. However, not all RealD 3D auditoriums have 4K projectors–many feature 2K digital projectors–so you may have to check with your favorite cinema chain’s Web site to find out which they use..

All Imax Digital 3D theaters, on the other hand, use Christie 2K dual-projector systems which give twice the resolution of full-HD and a brighter 3D image. What this means is that RealD 3D auditoriums with 4K projectors can provide a visibly sharper image, especially with movies shot on similarly high-resolution cameras.

Imax Digital 3D RealD 3D
3D technology Linear polarizing Circular polarizing
Projector Dual projectors Single projector (with 3D lens)
Screen Silver coated Silver coated
3D glasses Large format (for larger screen) Standard size
Audio Uncompressed Varies by theater

The 3D effect

A scene from sci-fi movie Prometheus, which was shot in 3D and released on Imax 3D and RealD 3D screens. (Credit: Twentieth Century Fox)

To some, 3D movies should “pop” out of the screen, similar to what audiences experience with 3D rides at theme parks. Others prefer a more subdued 3D effect that stays behind the screen, adding a little more depth to the standard 2D fare.

Those who prefer the reach-out-and-grab-you effect might be partial to Imax Digital 3D, which the company claims to excel at. Executive Vice President (Technology) of the Imax Corporation, Brian Bonnick, says that Imax Digital 3D movies “can appear in front of the screen” which may be more lifelike. He also credits Imax’s “patented theater geometry”, “proprietary wide-angle lenses” and brighter images for this effect.

If you’re not a fan of props being hauled your direction or swords almost touching your nose, then RealD’s 3D effects could be the alternative. While RealD technology is capable of extending beyond the screen, the screens used in these cinemas tend to be flat and positioned further from the viewer, which would minimize the coming-at-you effect. The 3D effect they produce would also be similar to what you’d experience on your 3D TV at home. Some videophiles also prefer the 3D effect to be behind the screen and not protruding from it, so that it does not serve as a distraction from the movie itself.

However, do keep in mind that some movies may be shot with effects coming out of the screen for dramatic effect–the James Cameron epic Avatar would be one example. Other movies, such as Prometheus by Ridley Scott, are shot with a more subtle effect, which can be equally believable. So it really isn’t all about the 3D format, but which movie you’re watching, too.

Is there a superior format?

Honestly, after watching a good number of Imax Digital 3D and RealD 3D movies, we’d say that the 3D effect is very comparable between these two formats. Imax 3D does seem a bit more dramatic, thanks to the larger screen and closer viewing distance, but the way the movie was shot is equally important. There are, however, some notable differences.

Imax screens are massive and curved, which should help improve your view of the screen and minimize ghosting–the appearance of a double-images that’s prevalent on some 3D TVs. Imax Digital 3D screenings should also be consistently brighter. Imax says that its linear polarizing technology provides an “improved signal-to-noise performance over circular polarizers” and “allows more light through”. However, keep in mind that this technology makes 3D movies less tolerant of movements, especially tilting your head sideways.

RealD 3D typically provides better viewing angles that allows viewers to tilt and turn their heads while watching. While 3D movie enthusiasts probably know that keeping their heads still minimizes ghosting or double-images, young children may not. RealD representative Rick Heineman believes that this flexibility is important for moviegoers who should be “free to sit comfortably”.

Another frequently overlooked aspect is consistency. While RealD theaters are far more abundant, the venues only need to sport “compliant digital cinema projectors”. This means that your moviegoing experience would depend on the type of projectors used by the cinema as well as the sound system installed–these can vary significantly depending on the brands of equipment used. Imax theaters, however, have to meet standards for audio and image quality which means they’ll look and sound more consistent across the board.

  1. Great article on the 3D standards. The biggest drawback to IMAX is there large glasses, which are reused and almost always have water spots. The size of the flimsy lens also picks up random glare from exit signs etc. They are very uncomfortable for me since I wear glasses. Why this issue wasn’t addressed and solved years ago escapes me.

    Real D does need to impose some standards on exhibitors. I saw “Avatar” in IMAX, 4k RealD and 2k RealD. At the time I wasn’t aware that there were different projectors used for RealD and I complained to management about the image quality. All screenings were at AMC theaters here in KC – headquarters to AMC Theaters.

    I decided on passive for my home TV since I could purchase clip-ons for my eyeglasses. I works great under all conditions. I don’t know why all home 3D doesn’t use passive RealD standard. I don’t see a meaningful difference in image quality from active, and more often than not, the retailers of active TVs tend to let their demos degrade or remain broken. I’m a life-long fan of Sony video, but have never seen a working Sony 3D TV in spite of trying dozens of times, including special trips to a Sony store where the salesmen were convinced I imagined the flickering I saw using every pair of glasses they had. All customers saw it. No Sony sales people admitted to it. No wonder 3D TV is slow to grab market share in the US.

    What is the Xtreme format being promoted by Cinemark theaters? Is it just large screen 4k RealD?

  2. Good article Timothy ! Congratulations !


    EXCELLENT ARTICLE IN THIS MOMENTS I GO TO CONSTRUCTION A CINEMA IN PUERTO RICO, I am Pablo E ILarraza Santiago owner of PEIS ENTERTAINMENT CINEMA is a company for the construction of cinemas with format 2D, 3D and 4 d with SONY and IMAX screens to make the experience of watching film a single along with technology and sound for the enjoyment of children, youth and adult, I am by listening people knowledgeable about film and theatre to find out how it should be cinemas in Puerto Rico where there is thousands of people that this is their favorite hobby I would like to know your opinion of what ought to be a movie theater to make them according to the taste of people who visit these new rooms.

  4. Heather Blair permalink

    Hi Pablo, if you are considering 4D please see me as I am Head of Sales for MediaMation. We are leading providers of 4D technology in themed attractions globally and now in cinemas, with our 1st installation in Mexico City with Cinemex. We happy to say NO THEATER is too big for our production facility. I have spoken to Imax in the US for 2 years… we think it would be great to see an IMAX film in 4D


      Thanks Mr Blair for the comment I want to make movie theaters with 3D screens whether IMAX or Sony with 4D in the Hall effects to create the viewer be part of the film and have an unforgettable experience. Also at the entrance to the theater there will be figures of artists in holograms by welcoming people to see the premiere of his films I believe to be innovative and would like visitors to the cinema.

      • Pablo, I can assist with the Halogram figures as well.
        Please give me a call.
        323 816 8240

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  5. I know that the newer projectors used for ReelD are capable of 48 fps and some at 60 fps (James Cameron is shooting the Avatar sequel at 60 fps). Are the IMAX Digital 3D projectors capable of the higher frame rates? I also wonder — if the IMAX projectors ARE higher frame rate ready — if they could run into some serious problems syncing the two projectors. The WETA folks were very concerned about that occurring with The Hobbit in 48 fps.

    • Going from 24 to 48 or even 60 progressive frames per second will only yield a mild visual improvement, and that improvement in visual quality is due to the fact that since there are more key frames overall, they will naturally play more smoothly than lower key frame values would. This means during filming they can use a larger apeture with a faster apeture speed than you normally would, there by capturing each frame with less “motion blur” (typically present in action scenes), or they wouldn’t have to artificially add motion blur during post (which is also a common practice) in order to smooth out playback.

      As for IMAX, I’m not sure exactly what the specs are for IMAX projectors, but I DO KNOW how TYPICAL 3D projection technology works. Currently, movies filmed at 24fps (23.976 actually) use “Triple Flashing” when displayed at the theater, meaning their actual frame rate is 144fps. You heard correctly. 3D projection TRIPLES the frame rate of the video source by triplicating each frame. It works by alternating between the images for the Left and Right eyes, three times for each frame, just like this: L1, R1, L1, R1, L1, R1, L2, R2, L2, R2, L2, R2, L3, R3, L3, R3, L3, R3, etc…
      This is done to smooth out the frames for 3D viewing, so there isn’t any noticable flicker, so you don’t vomit, that sort of thing.

      Since RealD uses a single projector with a circular polarized lense, that one projector MUST have a refresh rate of 144hz or some higher rate that is divisible by 144.
      IMAX 3D uses two projectors however, each with it’s lense polarized at a different angle. What this means is that IMAX projectors run with both of their projected imaged OVERLAYED, IE: L1 and R1 (from the example above) are shown on the screen AT THE SAME TIME (this is why IMAX movies seem brighter, there are literally two seperate lights projecting two seperate images at once). The added benefit to this is that since IMAX projectors ARE showing both Left AND Right images at the same time you can run your projectors at half the rate of RealD projectors and STILL get all the advantages of Triple Flashing. So really, for a 24fps 3D IMAX film, each projector only needs to be capable of 72hz, not the higher 144hz refresh rate of other forms of 3D film like RealD.

      Now for movies filmed at 48 or 60 fps (which they are dubbing “High Frame Rate” or “HFR” for short), they won’t be able to Triple Flash (the frame rates would be too high apparently), so what they will be doing is “Double Flashing”. Double Flashing is exactly the same as Triple Flashing except that each frame is duplicated instead of triplicated when being projected. So a 48fps film would end up being shown at 192fps, and a 60fps film would be shown at 240fps.

      Hope some of that is helpful.

  6. Thanks for the article. Two additions:

    1. Imax glasses, because they are linearly-polarized, can actually produce unwanted artifacts. Similar to if you shot a photo with a polarizing filter and set it to 0 degrees and then to 90 degrees, in one eye you may see light bouncing from the screen onto seat edges and other objects in the theater while the other eye doesn’t see these. Real-D doesn’t have this problem.

    2. With Real-D projection and glasses, it’s true that rotating your head will not cause crosstalk. But what’s also true is that you’ll start seeing a ‘vertical disparity’ rather than the desired horizontal disparity that 3d projection requires. Turn your head 90 degrees and you’re seeing no 3d and all vertical disparity (which is probably the biggest headache causer in 3d). The lesson — don’t turn your head, no matter how tempting.

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  8. Paz permalink

    Hi guys, nice article. thank you!
    But you got a mistake in there:
    It is not about a certain spectrums of light, it is about the wave-oriantation.
    Circular polarization filters work according to the same principle as linear polarizers. Optical gratings let only pass light waves with matching orientation.
    So you send out the movie in two different orientated signals. One Vertical and one Horizontal.
    The glasses on each side only let through wavelength of on of the directions.

  9. This is amasing i love it men wow

  10. Nick Anson permalink

    Can you use the same passive 3d glasses for both movie formats?

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  11. All I know is that, although I enjoy IMAX 3D, what I don’t enjoy is the glasses themselves! I must have a bigger head than some people, as when I leave the IMAX screen, I have a pain on both sides of my head & two indentations where the plastic side bits have been digging in!

  12. Shaun permalink

    You mention that 2K projectors provide twice the resolution of Full HD.
    The resolution for Full HD (FHD, 1080p, etc) is 1920×1080
    The resolution for 2K varies depending on cropping but the resolutions are normally 2048×1080, 2048×858, and 1998×1080.

    • joe movieman permalink

      What Its All About Is Apparently Over Your Head!!!!!! No, Just Kidding Its About How Un-Informed You Are About Movies!!!!!!!!

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  14. My wife and I tried watching a digital 3D movie at a local IMAX, and we had to walk out after 15 minutes and exchange our tickets for the RealD version of it…

    The fact that the right & left sides of the IMAX glasses were two different shades drove us crazy! Half the screen was lighter than the other; we might as well have been using those old red and blue glasses! We’ve used RealD ever since.

    • Genevieve permalink

      Thank you for this input. My eyes cannot deal with those kind of glasses. I basically get not 3d effect because of my severe keratoconus. I will be sticking with real 3d.

  15. Jared Ba permalink

    “Imax Digital 3D is an evolutionary improvement of the analog Imax 3D theaters that have been around since 1986.” Dumbest sentence I’ve read all week. You don’t go from 16k to pseudo-4k and call it an improvement of any kind.

  16. Thank you for this article! I always wondered what the difference between the two was. Due to your description of IMAX 3D I would love to experience it personally! Unfortunately, in Germany there are only 2 IMAX 3D cinemas regularly showing new movies and both are many hours away from my home town 😦

  17. Fred F. permalink

    The articles have been very informative but are bit dated for me at this time. I am curious if anyone has watched the new Star Wars movie and which way it is best to be seen.

    • Jay permalink

      This post is a bit late now, but regarding the new star wars movie, and all 3D movies in general, for me personally anyway, I far prefer IMAX 3D to Real 3D.

      For one not so important thing, Star Wars TFA was cropped off at the top and bottom to fit the real 3D screen, you lost a bit, not massively important or earth shattering but after watching it at IMAX in 3D first on premier night and then later on Real 3D, it was noticeable when a sound effects played with no accompanying visuals…

      Also another personal thing – I’m left eye dominant and right handed so maybe that’s why, but I was never able to see 3D on the old red green setups, and I can almost never see any 3D with circular polarised Real 3D. With red green I saw a red and a green image overlayed on each other with or without the glasses. With real 3D I see a slightly out of focus movie with the glasses. I have to stare really hard and try to not look at the main scene, but rather past and try to focus on something in the background, then the stuff in the foreground comes into focus, it’s hard work to watch a movie like that.

      IMAX 3D on the other hand just works. I’ve watched pretty much every AAA title that’s come to IMAX 3D in the last few years and I’ve never had a problem except when tilting my head about 45° and that is uncomfortable so why the hell would I wanna do that?

      Adding to that, here in South Africa the sound is positionally better at Sterkinekor’s IMAX and IMAX 3D theatres than it is at non IMAX theatres, or Nu Metro’s theatres. I’m assuming IMAX has a minimum theatre specification that has to be adhered to. You need rules in Africa or things go to hell really fast ;P

  18. MainFragger permalink

    The biggest advance in theater 3D was learning that they needed to use non-reflective ceiling materials in the theater. When 3D first came out, plastic trim around ceiling tiles, and white reflective ceiling tiles made watching 3D movies very difficult. The reflection would come down to the glasses and reflect right into your eyes. Once they went to non-refectlive materials, 3D movies became enjoyable..

  19. I just saw Return of the Jedi in Imax 3D and there was absolutely no difference from regular 3D in AMC theater in Oklahoma City. Sound: no difference. Screen: not curved. No difference. Price: $2 more. How come they can market as Imax?

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