By David Bush, Consultant and Director of Stereography
Many Cinematographers have learned through years of experience how to make projected films look “three dimensional” on the big screen, even though they have been projected on flat screens.
Lighting, lensing, colour, overall contrast, camera blocking and movements, editing, and many more techniques combined with the film’s sound have been used in many different ways to tell stories that sometimes have indeed seemed to jump out of the screen or pull us emotionally into the story line.
Additionally, the use of very narrow depth of field to focalize our attention, the creation of “depth planes” together with the slightly strobing 24 frames per second “filmic” look, have all contributed in some way to our belief and identification with the story being told to us; much of this, indeed, has been what we have perceived as the “theatrical experience”, giving us a heightened sense of immersion in the stories unfolding in front of our eyes on the big screen, letting us believe the unbelievable sometimes.
However, with the advent of stereo 3D, story telling gets a whole new added set of tools, and I believe that it can become stimulating to tell stories in a completely different way, as quite a few of the major international film directors have already discovered. Thanks to an added sense of depth now available, it doesn’t quite make sense to create it “artificially” anymore; in fact, it does indeed look a bit odd if we do try and make a 3D film in the way that we have always made traditional 2D “flat” films in the past.
I’ve recently heard and read that professionals in the industry complain that the current wave of 3D films seem very conservative in their stereo. The public often doesn’t perceive the added value of the stereo, and while some of this is down to the size of screens, the brightness of projection, the quality of the same and the types of glasses used in the cinemas, when not horrible digital 2D to 3D conversions, there are other causes too.
Some industry professionals think that this is because stereographers prefer not to risk over-doing the stereo, and I’ll admit that I’ve been cautious myself more than once, but, although there can be this too, I’m inclined to think that the relatively flat perception has also much to do with the large sensor formats that current 3D films have nearly always been shot with, with a resulting very shallow depth of field in the imagery. Using the habitual 2D widescreen format of 1:2.39 can also lead to less stereo perception than 1:1.85, as cutting out the ground also can mean that we perceive less stereo.
So, and without pretending in the least to offer an exhaustive explanation on the subject, here are some of the considerations that I feel I can make, following on from my own experiences in 3D film production and post, and which may, I hope, prove useful to those about to embark on filming in the format.
Starting from the basics, panning and tilting the cameras, and which are essentially 2D movements, don’t look all that hot in 3D unless used for minor adjustments in framing of Steadicam, Techno Crane, Jib and Track moves; whereas three dimensional movements of the cameras do indeed look much more interesting, as we are stimulated by continuously changing depth cues while we watch them; leave a stereo 3D shot with the camera locked off for a while, and it will soon look as if there is little or no stereo.
Another example; if we see a wide establishing shot with two people talking, we can see how far they are from each other in 3D space, so when we cut between them in close ups, there is not really any need to show the shoulders and backs of heads out of focus so that we can see where they are in 3D space, because if we do this in 3D then it will look awful, as objects in close up and out of focus look odd coming out of the screen into the theatre, and we already know where they are in 3D space anyway.
The accurate perception of depth means care must be taken with action shots where stuntmen are fighting, for example. We can quite easily see tricks that might have worked exceptionally well in 2D, like punches that appear to hit home on the adversary, but now, because we can see where things really are in three dimensional space, they need to be achieved differently.
The timing of scenes and shots changes, in as much as 3D stimulates and motivates a longer look at the surrounding scene. In this sense, I’ve noticed that the best approach to editing is to edit in 3D, and not in 2D first. If there is a 2D version, then this may well need a completely different edit, and it should be done afterwards.
I had joked with Dante Ferretti, Hugo’s excellent production designer, about the fact that he must have carefully chosen the many beautiful and refined objects for the scenes in Martin Scorsese’s recent film, and yet, I mused, haven’t you ever thought that we almost always see these objects out of focus in the finished film. He laughed. I said that it’s as if there were lots of large sheets of perspex smeared with generous layers of vaseline, hovering in front of the objects so that we can’t see them in focus. He laughed again.
I think I made my point. Personally I think that it is more interesting to see the background and set in focus in 3D, and set designers will probably not object, with their craft becoming more visible, so filmmakers should contemplate smaller sensor sized cameras to capture things in focus, gaining, at the same time the added advantage of greater mobility for the cameras.
To prove the point about smaller sensor cameras, I was once doing some interesting tests in 3D for a renowned Italian director. He was preparing a film at the time in which many of the scenes were to be shot in one room. He asked me if it were possible to make the audience feel as if they were in the same room as the actors. I suggested putting the cameras at waist height and very slightly tilted up with wide lenses, so as to create images with a similar ground perspective as that of the cinema where we would subsequently view them.
Keeping the left and right edges and the ceiling darker also helped to take away the idea of a “large window” that we are looking at in the cinema, even though the actors would be larger than life in the final projection.
His DOP insisted on shooting the tests with a pair of 35mm format digital cameras (Arri Alexas), but I also suggested shooting a backstage of the event with a smaller format stereo camera set. Out of curiosity, I asked the backstage cameraman to shoot all the Alexa set-ups too.
When the director asked to see the Alexa footage he was indeed very positively impressed with the effect, which was what he had asked for. I then showed him and the DOP the small format camera’s imagery, and this made him very excited. It was all in focus, so our eyes could look into every single part of the room and see it all in focus. The stereo looked much stronger. He would have much preferred that kind of end result, and stated that.
It almost goes without saying that subjective shots are far more interesting in stereo as we can feel where the subject’s eyes are looking much more than in 2D, so, apart from the mobility of the stereo cameras, which is indeed better achieved with the smaller format sensors, this brings up another point; the increased sense of realism that can be achieved if we use a higher frame rate for the film’s projection, say 48 frames per second (as per the Hobbit), or 60 frames per second (as per James Cameron’s Avatar 2 and 3); that which is now known as HFR.
This is a relatively new area of discussion, but I have done some testing of my own to see what happens; the first interesting result is a heightened sense of realism, which is complementary to the stereo 3D effect too. Another interesting advantage given by the higher speed timelines is a heightened sense of detail or resolution, something that can help smaller format, lower resolution cameras outperform their bigger brothers as our eyes perceive less noise, more detail and sharper images in stereo compared to 2D, and if we speed up the timeline, the temporal resolution increases all of this more still (as Douglas Trumbull discovered with Showscan some years ago).
So, although stereography isn’t just to do with smaller sensors, maybe these could indeed play an important part in creating stronger stereo in films.
David Bush is a freelance professional who has been working in the Film Industry for thirty five years. David is a Film Producer with a technical background and extensive experience in feature production and post production as Colour Grader, Editor, Producer, Stereographer and Visual Effects Supervisor/Producer.