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The Art and Craft of Converting 2D Films to 3D

05.10.12 @ 6:30PM Tags : , , , ,

If you caught this past weekend’s big blockbuster, Marvel’s The Avengers, then you may have watched it in 3D.  Many of you may or may not have been aware that the film was first shot in 2D and converted to 3D after the fact.  Wondering what that process involved?  Or why some films would shoot in 2D and then convert, vs. shooting stereoscopically from the start?  In a fascinating in-depth article, fxguide delves into the many challenges vfx artists face when converting 2D films to 3D — also known as “stereo conversion” — revealing the kind of pain-staking labor and ingenuity required as well as some of the aesthetic differences between the two formats:

Now, 2D-to-3D got a pretty bad rap after Clash of the Titans came out — it was one of the first films rushed through a 2D-3D conversion job by a studio looking for that 3D cash-in.  But since then, studios and vfx companies have put significant resources into advancing the tools and workflows that make stereo conversion possible — in the process making for some truly good-looking 3D films out of 2D shot films.  They have applied the process to older movies like Titanic and the Star Wars saga, and newer ones like Transformers: Dark of the Moon and John Carter – either to your general entertainment or chagrin.  Regardless of how you may feel about the reasons for converting movies, reading through the guide you’ll learn a lot about the sheer challenges of doing things like transforming a busy, rainy street scene — a process that may involve rotoscoping individual drops!  Not only that, it also drives home some of the technical challenges of 3D in general — whether it’s a conversion job or not.  Take, for example, the idea of “floating windows”:

One technique that Bob Whitehill has used extensively, but was not used on films like Avatar is ‘floating windows’. This technique aims to get around the limits in one’s stereo ‘budget’, in relationship to the edge of the screen. If a character is closer to camera – as in an over the shoulder shot – it is hard to have them sitting in stereo space closer the audience (ie. ‘in the space’ between the screen and the audience, since their body is cut off by the bottom of the real cinema screen). As our eyes can see the stereo image is floating closer to us than the edge, yet our minds ‘know’ the person must be on the other side of that screen or window, we mentally reduce the stereo effect.

In other words, the illusion is lessened since we know that someone cant be close to us AND further away behind the sharp real world edge of the cinema screen. The trick that Bob Whitehill did not invent but radically perfected at Disney was to float another dummy edge of screen between the viewer and the stereo violating back of the shoulder. This floating window is rendered in the footage, but tricks the audience into thinking the edge of the real world cinema is closer than it is – hence not violating the edge (this effect is known as an edge violation) and thus we regain some of the stereo budget. That is the useful working space one has to place things between a sensible close and a sensible far in stereo terms.

With a section that lists common techniques and tools of the trade, along with case studies of many of the movies mentioned above, this really is a great read if you’re interested in stereoscopic film, period.  For the full guide, check out the article here.

I watched The Avengers in 2D, mostly because I get headaches with 3D movies (even ones purposely shot in 3D).  I thought it looked great.  Did you get a chance to watch The Avengers in 3D?  How about the Star Wars conversion?  How did they look?

[via fxguide]



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  • I’m not a huge fan of 3D. I personally don’t like its aesthetic and would much rather watch a well-composed 2D shot than something with added dimension.

    One thing that threw me off when watching Avatar (my first 3D experience) was that my brain really didn’t like shots with shallow depth-of-field. It desperately wanted to look at other objects that were out of focus in the scene, but my eyes somehow couldn’t (of course).

    I am intrigued, however, by some of the new storytelling dynamics offered by 3D. I think I heard somewhere that the eye can pick out more details in a scene more quickly with 3D because of the different planes on which those details reside. Would anyone be able to elaborate on this?

    Great post, E.M.!

    • E.M. Taboada on 05.10.12 @ 7:23PM

      Thanks, Gabriel! That’s an interesting thought on whether the different depths make it easier to scan details in an image. I’d love to hear more if anyone knows about that.

    • Daniel Mimura on 05.17.12 @ 5:19PM

      I personally think you are able to scan a scene in 3D *slower* than you can in 2D.

      One reason it wouldnt be any faster is b/c in real life, your eyes get depth queues by where you are focusing. As Walter Murch has pointed out (I will not send a link, as I see it mentioned further down in the comments here), your eyes are focusing on only one distance…the distance from your eyeball to the screen. Don’t underestimate motor memory/muscle memory. People don’t consciously think about it with their eyes as much as their bodies, but it’s the same thing. As a steadicam operator, skateboarder, and motorcyclist, my life and livelyhood depends on these skills. 3D is inherently false to me b/c I cannot trust my own eyes. It’s always nice to learn to adapt to new things, but it’s completely unsettling to not be able to depend on the very things that I depend on to make my living and survive in the first place.

      Another reasons scanning and comprehending an image is slower in 3D is because of the changing convergence points from shot to shot. I forgot which issue of AC (American Cinematographer) I was reading recently, but they were talking about how shots have to last longer in 3D—you can’t comfortably cut as quickly as 2D b/c your eye has to adapt to the changes in convergence from shot to shot. So, I take this to mean that they were saying that it takes *longer* to comprehend an image in 3D.

      So, once again, the effect is inherently inhuman and unrealistic—b/c we are not snails and cannon adjust our own occular distances, meaning that changes in convergence are inherently inhuman and unrealistic.

  • The fact that you chose to see it in 2D rather than 3D speaks volumes. Walter Murch wrote a pretty good argument against 3D in general; – but retrofitting 2D films just seems to exacerbate this. On top of this, it increases the “cut out” effect. I appreciate they were isolating characters in some shots for ‘up to 7 depth areas with separate z values’ (I’m paraphrasing), but if I look at a person I can perceive a lot more than 7 areas of depth in them. This is perhaps the worst case of the “fix it in post” mentality that I can think of. I struggle to see how it genuinely makes sense to have an army of rotoscopers and compositors doing the job of a stereographer on set.

    Ok, rant over!

    • E.M. Taboada on 05.10.12 @ 7:51PM

      I hear ya on the fix-it-in-post mentality. To be fair though, the article points out that there are certain situations where it’s not feasible to do it stereo in-camera (i.e you’re shooting on film ((maybe the camera size is an issue??)), or using anamorphic lenses). For example, John Carter had that double-whammy. Even though they had always planned on releasing it in stereo, they still shot it anamorphic on 35mm film. Personally, I like watching my films in 2D, so I appreciate filmmakers who still put the 2D image ahead of 3D concerns (which is what I feel Stanton did in that case). All the same, I’m looking forward to watching The Hobbit in 3D, I think 48fps might actually help 3D. I’m still waiting for that 3D movie that really takes me somewhere I can’t go with 2D. I guess we’ll see!

      • John Carter looked absolutely stunning in IMAX 3D. I think that it has been my favorite 3D experience so far (even more than Avatar). The fact that I’m finding out now that it was post-converted makes me like it even more.

        Clash of the Titans had soured me with 3D. I wish I had seen Avengers in 2D. Spiderman I WILL see in 2D (the previews gave me a headache). Prometheus looks quite promising in 3D. I’d rather watch it in 2D, but I’m dying to see it in IMAX and now most IMAX features are only available in 3D (ugh!).

        I still like 2D better…

        • Will Gilbey on 05.11.12 @ 12:35AM

          Respectfully disagree. Thought John Carter was one of the worst post conversions I’ve seen. Totally ruined the film for me. Primarily because Andrew Stanton clearly wasn’t thinking about the 3D conversion while he was shooting – so many longer lens shots that just looked like cut out pop-up books. Also I just can’t get behind how dark and muddy films look in 3D – anything shot at night or in low light just doesn’t seem to work.

        • Daniel Mimura on 05.17.12 @ 5:34PM

          Just so you know, most IMAX films in 3D are *not* real IMAX…

          Fake IMAX is under 3K resolution…you’re generally better seeing it with Sony 4K projectors…don’t pay more for fake IMAX.

          Here’s a link to real vs fake IMAX:


          And here is a link to about the whole fake IMAX thing. Don’t be suckered. It’s a scam.

          I saw Inception in 4k Sony, and then saw it a week later in IMAX (or so I thought), paying more…and I couldnt figure out why it sucked worse, thinking I’m watching a 15perf 70mm print and shaking my head trying to figure out why it looked so bad…

    • Just so you know, there are stereographers at conversion companies. The tell the compositors, roto artists, and depth artists what to do. They control the overall depth of the film too, (as well as the director in most cases.) Joss Whedon and his people chose to have Avengers in a safer, more manageable range of depth for various reasons such as the fact that children and adults have a different IO and depth perception as well as

      • …the fact that the more depth you put into a scene, the greater the “pixel gap”, which is the side-effect of transforming one image into two and the artists have to till these gaps with information that never existed, either by clean plates or just straight painting it in. So the more depth you have, the more work it is to make it seam-less and the more expensive it is.

        • *fill. Anyway, with that said you can see the difference with Titanic because more time and yes, $$ was put into adding greater depth, which made it much more pain-staking. And of course because Cameron is the greatest supporter of 3D. All you 3D haters can probably blame him for all this if you feel like you need someone to blame.

  • Transformers was shot in 3D, wasn’t it? I will say that Michael Bay’s style of filmmaking definitely lends itself to 3D movie making. Thing blow up IN YOUR FACE!

    • E.M. Taboada on 05.10.12 @ 7:17PM

      It was shot partially in 3D on set and partially converted in post (i.e for stuff shot on film, and for some VFX). According to the article, they converted up to 77 minutes worth of footage. Interestingly, Avatar also had a bit converted in post (i.e the eyeball shot at the beginning) because the 3D-rig is too big for that kind of macro close-up.

  • I did watch The Avengers in 3D mostly because the 2d one was already packed. For me it doesn’t add any value to the movie and costed me 3 bucks more. For better 3D movies you should always check animated ones where the animators and layout artists have total control of camera framing and camera convergence settings, also the editing is worked and re worked in parallel to get the best 3D experience, it also applies for movies like Avatar since it was almost all CGI, still… I don’t like

  • I also saw Avengers in 3D for the simple fact that the 2D showings were sold out. While I thought the conversion was skillful, I didn’t feel it was “deep” enough to really affect my perception except in a few scenes where there were pronounced foreground elements like the glass in front of Loki’s containment chamber.

    Kudos for fxguide, a wonderfully written article.

  • I went to the Avengers 2d and the screen was so tiny and dim, I think the projector was using a 50watt bulb. I asked to change to the 3d show and it was so much better! sometimes they don’t take off the 3d filter on the 2d shows because they only have one projectionist to run everything.

    • Also, some projection systems (Sony) have DRM systems that include lens identification. Change a lens wrong and it will freeze the projector.

      • Daniel Mimura on 05.17.12 @ 6:02PM

        I’ve read that article or a similar one…I think the title is misleading…Sony 4k projectors aren’t “ruining 2D movies”…lazy projectionists and/or theaters are!

        I have talked to the local and regional management for Regal theaters…they won’t take off the polarizers that Sony projectors put in front of certain models of projector, so I just don’t go there anymore. (Note: peek your head into the projection booth…if you see 2 rectangular polarizers (mounted in one bracket) in front of the lens and you’re watching a 2D movie, complain, demand your money back…etc. this doesn’t work for every projector system, but if you see that attachment, it definitely needs to removed b/c a pola will take away up to a couple stops of light. This adjustment takes a couple minutes.

        There is a little more about it on the Alamo Drafthouse blog, but keep in mind, they’re one of the few theaters doing it right…it takes like 45min or an hour to switch out the dual lens setup of Sony 4k’s…(which they will do if they are not switching between 2D & 3D in one day…even thou projecting 2D thru 2 lenses isn’t ideal, there is no light loss…the loss is from the polas.) When he is “agreeing and disagreeing with Roger Ebert about theater brightness”, I thinktheyaretalking about different things. Movies are noticabely brighter there than any big chain I’ve gone to. And the dimness Ebert is often talking about is b/c the 3D glasses take away light (plus you are only getting half of the picture to each eye, which in its own ways literally 1 more stop of light loss, if you want to look at it that way.

  • I saw just HUGO CABRET in 3D and I think but I think is enough to develop an opinion about 3D. I think 3D is distracting for 2 big problems: shallow depth of field doesn’t work, everything in the frame should be in focus and our eyes can decide what to look. The other problem i noticed is motion blur in action scene, thing that maybe will be fixed shooting 48fps or more. Fortunately I saw The Avengers in 2D, and I really enjoyed it, I think watching in 3D can be really distracting, specially last battle scene, half an hour of action scenes could be really stressing and confusing, losing the joy of the movie.

    • For a “real” 3D effect your eyes should be able to focus around the frame, and the respective parts should go in and out of focus – like in real life. But that doesn’t work obviously.

      3D for me only works properly in animated films right now – however I still find it unnecessary.

      Maybe 3D gets better over time and I will like it in the future. But I wouldn’t miss it if it disappeared…

  • Neill Jones on 05.11.12 @ 6:10AM

    I feel the studios rushed through 3D as they saw it as their next cash cow, it’s a good excuse to increase ticket prices, prevent piracy and boost home equipment sales. Unfortunately the technology stands out to me as not ready coupled with a lack of experience using it. The final nail in the coffin for 3D for me was Thor, 2 hours of squinting at a blurry image takes you out of the experience and is just not worth paying for. I might be tempted to have a look at the hobbit with it’s 48fps which is probably where they should have started from in the first place.

  • Transformers: Dark of the Moon was converted from 2D? I thought it was shot in 3D.

    • E.M. Taboada on 05.11.12 @ 3:33PM

      Check out the fxguide article, it goes into some of the details of what they did. Also, another great post about the partial 2D-3D conversion done on Transformers 3 can be found here:

      It’s a really interesting read in itself, as that author worked on the process, and gives his thoughts on the pros and cons of doing 3D after the fact vs in-camera.

  • I just really liked Jackass 3D, it really used 3D well… as silly as that sounds.

    • Funny you should say that, parts of it were converted by the same company that worked on Titanic and Avengers.

  • I just saw Hugo Cabret and The Avengers in 3D. Allthough i really hate action movies plus i think superhero movies are stupid as fuck, i really enjoyed watching The Avengers in a german CinemaxX Maxximum 3D (dont know if its 2K oder 4K). Could be the better seets or the bigger/better Cinema, but The Avengers looked far superior to my eye.

  • Stu Mannion on 05.12.12 @ 4:56AM

    Avengers 3D was my first post-converted 3D experience. I’d heard so many bad things about the process in Clash of the Titans etc I was interested to see what it looked like. I have to say I was impressed. It was very clear and bright. It made me think that the post-converted 3D experience was perhaps more pleasing to me (when done well) than shooting stereoscopically. Maybe this is because they have more control in post to fine-tune the 3D effect and, when they’re shooting, they’re doing it the old-fashioned way – with all the standard ways to make it look great.

    I think of watching a 3D film like snorkelling. Yes it hurts my eyes a bit but it does add a little immersion for me – perhaps not enough to keep me choosing it.

  • Avengers 3D was the worst 3D I’ve ever seen. Absolutely hideous conversion. No sense of depth whatsoever and taking the glasses of intermittently it was essentially just like watching the 2D film with dark sunglasses on. I did however see Titanic 3D at the IMAX recently and it was absolutely stunning. I guess the lesson is that James Cameron is still the only guy who properly knows how to use 3D. I think the truth is that he a) Cares more about it than studios who, as you say, rush the job in post for extra ‘wow’ factor, and b) Probably has the cash to do it the way it really deserves to be done.

    • Its frustrating to read a lot of the complaints on here because most of the people don’t actually understand stereoscopics or even know the difference between conversion and native shot 3d. I actually worked on the conversion for both Transformers 3 and Avengers, (worked for 2 different companies.) What people don’t realize is that there is no “real 3D”, its all an illusion, whether its converted or shot. If it were real, you’d actually have to be there seeing the situation with BOTH of your yes, (this is how you see depth), without any glasses forcing one image into each eye. Shot 3d can look horrible too if its not done right, people don’t understand that its not like you just take a 3d camera and go shoot stuff. The inter-axial, or inter-ocular, settings of the camera and the lenses all affect the depth and the volume of the characters. Sometimes conversion can do a better job than the cameras can. Yes a major chunk of Transformers was converted, and people still deny this, and yes parts of Avatar were as well. I honestly don’t think the majority of the complainers on this thread know the difference other than what they heard or read somewhere. A lot of people also mistakenly judge 3D on how far things come out of the screen, that is not what 3D is all about. there is zero parallax depth which is your screen plane (most of the time the focal point of the movie is set at this depth), then there is negative parallax depth which is what comes out of the screen, and positive parrallax depth which is what goes into the screen. Where things lie within this space is up to the director and stereographer, it is an art and a science. You wouldn’t want everything coming out of the screen because for one it would make your skull ache, and two because it throws off the scale of things. If 3d is done wrong then you might notice things looking minature or gigantic, as in out of proportion to how you’d expect to see them in real-life depth. A lot goes into these decisions. I think some of you should show some respect, you don’t have to see movies in 3D but you shouldn’t act like you want to boycott them or something. Believe it or not this is doing a lot for the economy and its creating jobs for many artists trying to get into the film business such as myself. This is an intricate process, we don’t just push a button and have the computer do all the work. Every character, every element, every object has to be rotoscoped and cut out of the shot and individually “sculpted” or built. We define the anatomy of a character more, we push reflections deeper than their surfaces, we shape objects , and push and pull things throughout an artificial space. yes, there is a lot of bad 3d out there but that is because of lack of budget and time. Not all of the people behind 3D are just trying to make a cheap buck. There is an art to it and there are those of us that care.

      • BTW TITANIC AND AVENGERS WERE CONVERTED BY THE SAME COMPANY. I actually touched a couple shots for Titanic as well. Titanic just had a better budget and the artists were given a year to do the conversion rather than just a few months. Don’t make assumptions

  • Well, it seems there are a lot of non ‘likers’ of the 3D format. As you can guess, I really love it. I’ve been in ‘the movies’ for a really long time and that is for the reason of ‘escapisme’. Bringing me into that other world with a sort of realism and then beyond. Using the 48fps system etc. is the next logical step, but i think I’ve been to much trying to mimic that ‘film’ look that I’m pretty confidend I won’t like it. Although i think it will have it place on certain movies. That being said, I think the content, the story, and the way a movie is brought will also include the decision of using a 3D format, or for the future 48fps and beyond… I enjoy it and look forward to each 3D movie that comes out, nevertheless that some are (due to the early stage of 3D) not yet up to the quality we need to have a + experience. If you look at the amount of different film stocks, colorgradings aplied, certain bizar graphic looks etc. it’s all about augmenting the experience. I think 3D has finally come and so it should, but only if used in the same appropriate way as the other esthetic elements. As of compairison, be aware that the current ‘glasses’ and projectors are the worst we will have from now on… I’m certain that everyone has the same issues with the fact that thise glasses are way to small and don’t have a peripheral view as should… also the projectors mostly don’t have the amount of light needed to have a good lit screen for 3D…. but things will only get better, and I’m looking forward to that.
    Those having headaches looking at 3D movies, blame the moviemaker not the system itself I would say. We (filmmakers) have a huge job to do in understanding the way the eyes, brain work and it will only get better.. I’m sure… Mr Cameron certainly is amongst the top ‘users’ and advocats for the ‘best’, but that doesn’t mean it won’t get better in say the next 10 years… It will and it should. I’m fortunate enough enjoying these movies without the headaches, even at my home projecting BluRay’s… It certainly makes me wanna buy and collect movies again. (even if I have all Star Wars movies bought about 6 times in different formats… ;-)

    • Daniel Mimura on 05.17.12 @ 6:15PM

      There are many different reasons for the headaches and I definitely blame the system for some of them.

  • Daniel Mimura on 05.17.12 @ 6:33PM

    I have just as much of a problem of post conversion to 3D as I do colorization. (Note: I don’t have a problem of post-conversion of films designed to have it added in post like that awful looking sequel to Clash of The Titans. That was shot 2D, but it was designed to be 3D from the start, unlike the first one.)

    Screw this 3D Star Wars/Titanic crap. It’s just as offensive as seeing Casa Blanca in color. Grrr…

    I don’t mind 5.1 sound tracks to silent films though, because these were accompanied by live musicians, so 5.1 sound gives you the fidelity you got in the first place seeing the film in the theater. Most screenings were just accompanied by a piano player on an upright, but premieres and upscale screenings were done with full orchestras…so watching these modern home versions are making it like top notch theatrical versions as much as possible…not revising it into something totally different.

  • Star Wars Ep. I was converted by Prime Focus and they outsourced the majority of the work to India, which is one of the many reasons why it suffered. The good news however, is that Stereo D who did Titanic 3D, will be taking over the remainder of the Star Wars films. Of course no one really cares about the prequels, but at least you know in a few years the original saga will be getting the treatment they deserve. All the haters won’t see it, so don’t even bother crying about it. I think it will be cool at least, since the last attempt was so lousy. I think when films like Star Wars and Jurassic Park are taken with as much care as that of Titanic, it will restore some faith in 3D. A few rotten eggs has given it a bad name but it just needs more changes to shine. Stop hatin’!