3D Shooting Guide
One should approach these guidelines with an open mind. They are not hard and fast rules. As rules, they can be broken by using the artifacts of stereoscopy creatively providing the artist wants to experiment.
- Live action 3D is generally a wide angle lens medium using movement and positioning like humans do in daily life. Of all techniques to be aware of, Wider Angle Lenses, Movement, and Positioning are fundamentally important. This is not a firm rule, but a fact that Stereoscopy mimics real human visual awareness.
- Most good live action 3D is shot by constantly moving the camera to set up visual perspective cues. moving laterally or diagonally through a scene amplifies spatial cues which is 50 % of most 3D sensation.
- The theater space is generally divided into three areas 1) front of screen 2) screen plane 3) behind the screen. Subjects can flow seamlessly though these planes of space under proper stereoscopic capture methods.
- It is far better to move in or reposition closes and not zoom into a close up. A zoom lens move will not force the subject into the theater space.
- To bring the subject into the theater we need to move the camera to the subject and keep all important elements of the subject in the frame.
- Zoom lenses must be used with extreme care as it is very difficult to track and correct zoom lens optical alignment on the fly or even as fixed prime lenses. There are companies specializing in correcting this annoyance with very powerful digital re-purposing technologies during capture; Most of which requires additional on set hardware and expense which can be daunting to the flow of most productions.
- Telephoto lenses require careful application that can result in flat layers of subject space “cardboard cut outs.”
- Using wide inter-lens axis spacing or i/o (for inter-ocular); the separation between left eye and right eye cameras must be used appropriately. This technique in the extreme form is called “Hyper Stereo” The only net result of hyper stereo technique making the subject appear smaller in the theater. Beside convergence control Hyper Stereo is one of the most misunderstood conditions of 3D image capture. Some use wide i/o thinking it will create stronger 3D and bring the subject out into the theater for a better experience. This is only true in that as the subject comes closer it is a physical fact that its size must shrink because of the vertical viewing angle required forcing the subject into your eyes. The bottom line for hyper stereo is that while crossing the boundaries of normal scale our eyes and mind struggle to keep things the correct size the way we see in normal life. Once the 3D theater breaks down our perception ( by hyper stereo) our mind collapses into a state of this person place or thing is way too small and I am way to large.
- Convergence is a term used for several aspects of stereography. It is a necessity in our human vision and in stereo cinema. However the term can be applied to several conditions describing 3D capture and play back. Two most common are the convergence point of aiming lens axis and the convergence point of our eyes when looking through 3D glasses at our favorite subject in the theater. The later is the way we naturally view all things around us. The stereo camera mimicking the same way we see life can do this only as well, if it is set up to record the way we see life. (unless we are fooling the audience by intentional rule breaking).
The problem with 3D cinema is that we cannot jump out of our seat and run to the subject to get a closer look. So the camera must do this for us. The director moves us to the subject for a closer look but we are locked in theater space and theater geometry and theater feeling. The camera must then create the sense of getting closer by creating a larger image for us and increasing the apparent distance that we are to the subject by our built in stereo viewing eyes. The only way to make us closer to the subject is to bring the subject to us at our seat so we feel we are moving in. The stereo camera the lenses must be set at the spacing of human eyes, looking out to infinity (parallel) and drive in closer in order to achieve this. The lenses always aiming at infinity and moving closer have brought the subject into the theater. There is no way to do this by any other method.
At some point we will be too close for comfort and have to make adjustments – just like we do with our eyes in real life; But we are now close and it feels close and looks close. In order to get really close we must start to do what our eyes do and use convergence. So the camera lenses converge and the result is pushing the subject slightly farther away from our eyes so we can see it.