I saw the new Hunger Games movie over the weekend, and really enjoyed it. Director Francis Lawrence (who helmed both Constantine and I Am Legend) did a great job taking over the reins of the production when Gary Ross left after the first movie. And to both Lionsgate and Lawrence's credit, the movie wasn't shot, converted, or released in 3D. Instead, Lawrence and his cinematographer chose to shoot a portion of the movie in the IMAX format. The final 50 minutes, to be exact. If I had known that before buying my ticket, it's what I would have chosen to see. But I've been skipping on IMAX screenings of late because the experience isn't the sure thing it was five or ten years ago. Back then, you knew exactly what to expect when buying a ticket to watch an IMAX documentary: gorgeous footage shot on 70mm film projected on a screen at least seven stories tall. But IMAX as an organization has expanded its brand to include lots of different types of "experiences", including the infamous converted IMAX theaters that Aziz Ansari railed on back in 2008.
In promoting the Hunger Games movie, IMAX executives spoke with movie blog Slashfilm about the current state of IMAX technology, and they maintain a consistent baseline experience for audiences. Despite some of the marketing-speak, there's some good insight into how IMAX current works, and what you should look for when deciding whether to pay a couple extra bucks to watch an IMAX-branded film.
There are three things to think about when considering watching IMAX film: how the movie was shot, how it was edited and processed, and how it's being projected. An IMAX shot Hollywood film, like The Dark Knight, is generally understood to have some of its scenes filmed on 70mm IMAX cameras. This 70mm film negative has many times the area of a traditional 35mm film negative, allowing not only for more detail but much more pronounced depth of field. According to IMAX, 35mm film has a digital equivalent of 6000 lines of horizontal resolution (6K), while 70mm film has the equivalent of 18,000 lines of digital resolution (more like 12,000 in reality). IMAX film cameras are heavy, loud, take a long time to reload film, and have limited mounting options on camera rigs, which is why no Hollywood film so far has been filmed entirely in 70mm IMAX. Christopher Nolan and Wally Pfister toyed with the idea for The Dark Knight Rises, but ended up shooting two thirds of the movie in 35mm.
How the director and cinematographer choose to shoot the non-IMAX parts of their movie also plays a big part in the viewing experience. Quick and seemingly random cuts between IMAX and non-IMAX shots can be extremely jarring, as in the fights scenes of the second Michael Bay Transformers movie. Putting many or all of the IMAX scenes in large blocks of the film, as Hunger Games: Catching Fire does is much more palatable. But even the non IMAX camera can be important. Today's digital cinema cameras, like the ARRI Alexa and RED Epic, have image sensors with a bigger frame than a 35mm "full-frame" equivalent that's closer to IMAX's aspect ratio. That means scenes shot with both IMAX film and those digital cameras can be edited more smoothly. And in the case of last year's Skyfall, cinematographer Roger Deakins was able to use an ARRI Alexa to shoot an IMAX film at a relatively tall 1.89:1 aspect ratio.
IMAX doesn't always mean film, either. 90s-era IMAX documentaries shot in 3D used a special IMAX 3D camera setup, but Hollywood directors find it too big and loud to use on location. So IMAX has developed a digital camera for 3D filming, using the same image sensors found in Vision Research's Phantom 65 camera. IMAX concedes that this digital version of their format doesn't match the resolution of its film cameras, but it's good enough for their purposes and can use IMAX developed lenses. Transformers 4 will be the first Hollywood film to use this camera.
Regardless of how a modern film is shot, it likely gets converted into a digital format for editing--a process called the Digital Intermediate. Most 35mm films go through either a 2K or 4K resolution intermediate process, then "scaled" back up when printed on film for projection. That means the film unfortunately loses some of the original detail in the negative, but the process is necessary for color grading, grain reduction, and adding digital effects. Christopher Nolan actually cut some of The Dark Knight Rises from the original IMAX negative to retain all of its image quality. IMAX has its own proprietary DI procedure called DMR (Digital Media Remastering), which is how 35mm films get upconverted to the IMAX format. The vast majority of "IMAX" films that you see in IMAX screens today are DMR films. Wikipedia has a comprehensive list here. IMAX has been vague about the specifics of its DMR process, and it's understood to be constantly evolving. The first DMR films in the early 2000s received mixed reviews from both audiences and filmmakers, but re-releases of 35mm films like Jurassic Park in DMR IMAX has been well received.
The DMR process also means that IMAX doesn't have to projected as 70mm film, either. In 2008, IMAX introduced a digital projector system for its DMR movies, which are played off of the company's proprietary IDF file format. The AMC converted "fake IMAX" theaters use these digital projectors, which are two 2K projectors that run at the same time for a brighter image. IMAX only began testing a 4K laser digital projector last year, which won't be deployed until 2014. Some older IMAX theaters even have dual-projector systems that allow projectionists to switch between 70mm and digital projectors depending on the film, so you're not always guaranteed the actual 70mm film experience even if you go to an older, trusted, IMAX theater.
Those are just a few things to think about the next time you're at a box office deciding which version of a film to watch. There's a case to be made that IMAX has been diluting its brand with its aggressive expansion into more theaters, but I think it's more that IMAX just hasn't been able to reconcile the state (and costs) of modern moviemaking technology with the standards and expectations they set when the format debuted in the mid 70s. Camera, editing, and projection equipment will keep getting better to a point where the different intermediate steps can't be differentiated. But any smart filmmaker knows that these are just tools, and that a great film is much more than the sum of its technology.