Friday, December 28, 2012

High Frame Rate Cinema Thoughts

I was able to get to the only theater in Indiana to see The Hobbit in high frame rate 3D, and I liked it!  I had already seen it in standard frame rate 3D and the comparison was interesting.  High frame rate, as it is used at present, is a film shot at 48 frames per second and displayed at 48 frames per second.  Since the 1920's the standard frame rate has been fixed at 24 fps, this has to do with sound recording and playback quality.  24 frames per second is the slowest possible frame rate that allows for acceptable audio at the time, that is, film costs money and filmmakers are either cheap or poor, so the frame rate is as slow as possible while still being watchable.

Douglas Trumbull pioneered HFR technology with film in the 1970's, Showscan [1] [2], which shot and displayed at 60 fps.  The technique runs through film stock at 2.5 times the normal rate and was too expensive to become commercially viable at the time.  With the advent of digital technology the added frames are more manageable and affordable than film.

Visual Aesthetic

I like the added temporal resolution of the HFR technology, meaning we get to see twice as much information while watching the movie. The HFR really shines with slower camera movements and action as the clarity of the scene is incredible. I particularly liked the early scenes introducing us to the Dwarven kingdom of Erebor, the views were stunning.  I had noticed several of the camera pans juddered quite a bit in the 24 fps version, but they looked very clear and detailed at 48 fps.  The faster action scenes were also benefited by the temporal resolution boost, though to a lesser extent which may have to do with exposure time per frame (more on that later).  The fight scenes, especially in Goblin Town, had a lot of cuts and quick edits that seemed to be more pronounced and visible in HFR.  Remember, editing is the Invisible Art, if I'm aware of the cuts, something is calling attention to them.  I think the art of the edit will need to adapt to high frame rate cinema to become invisible again.

Technical Thoughts

Standard frame rate cinema means 24 frames per second, with a standard shutter angle of 180°, means each frame is exposed for 1/48 of a second.  This means that slower motion is captured clearly and sharply in each frame while quicker motion exhibits some motion blur in each frame.  At the slower frame rate of 24 fps, this motion blur helps blend the frames together when projected to smooth the action, but it is really lost information.  This motion blur is a lack of detail and clarity of information.  Christie has a nice page about HFR.

HFR, in the case of The Hobbit, means 48 fps, with a 180° shutter angle that means each frame is exposed for 1/96 of a second (though a digital camera could expose a 360° shutter for 1/48 of a second per frame), this means much less motion blur per frame and more detail and information per frame.  A post in this forum thread talks about The Hobbit being shot with a 270° shutter angle as a compromise to best show 48 fps and 24 fps versions of the movie.

The toss-up here is the greater temporal resolution of the 48 fps and the reduced motion blur of a shorter exposure time per frame leading to the action scenes in The Hobbit being perceived as shuttering (this is different than judder).  A great example of shutter are the fight scenes from Gladiator.  I think this is a trade off, greater temporal resolution for shuttering, though I think that our threshold for perceiving shuttering is something we've learned from watching movies filmed with a 180° shutter for the most part, just like we've been conditioned to expect movies to "look" correct at 24 fps.


All in all I liked the movie and the exploration of new technologies for storytelling.  Staying with 24 fps movies for no other reason than "we've always shot at 24 fps" seems problematic.  Let's explore 3D, let's explore HFR (James Cameron will shoot the Avatar sequels at 60 fps and Trumbull is shooting 120 fps with Showscan Digital), let's explore new cinema.

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