How does 3D work?
With the huge financial and critical success of films such as Avatar and Alice in Wonderland as well as major live sporting events, it is clear that 3D has finally arrived. The phenomenon of s3D has galvanised audiences across the globe, but what is s3D? How does it work? And what are the processes involved for s3D production?
Firstly, the need to understand how the eyes and brain work is the basis for understanding s3D. Our eyes and brain actually use eight depth cues to estimate depth and create a s3D image of the world around us. Lighting and shading also help to estimate the relative shape and position of objects. However, it is the last two cues, vergence and stereopsis that provide us with the most powerful depth cues.
Vergence:
This is the effect where our eyes slightly converge towards one another when we focus on an object near to us.
Stereopsis:
This is the small difference between what our left eye sees and our right eye sees.
3D Video:
This works by making use of two cameras to simultaneously record a scene. The cameras are set apart, roughly the same distance as the human eyes, this creates two separate images, and these two images are then merged into a single image. This is shown on display using s3D glasses and creates an illusion of depth that we know as s3D. s3D glasses will then split the image back into an image for each eye, convincing the brain seeing s3D.
Another important part of viewing s3D is the concept of parallax; this is the difference in the apparent position of an object viewed along two different lines of sight for each eye.
The understanding of parallax affects the end results and is crucial if you are to produce quality s3D.
When producing s3D, it is also vital to consider how the cameras will interact together, common mistakes include:
- Vertical or rotational misalignment
- Unmatched zoom tracking
- Poor focus
- Excessive convergence
The above points can easily distort the s3D illusion. However, we have made substantial investments in s3D, and much of the common mistakes can be rectified automatically with our Sony MPE-200 Stereo Image Processors, which is able to correct these issues in real time.
In post production there are still a number of things which need addressing. Fast cuts and zooms can provide an uncomfortable viewing experience, as the audience’s eyes constantly have to refocus, which can lead to headaches. This is why s3D productions should always be supported by experienced technical crews, something that Presteigne Charter prides itself on.