How Does 3D Photography Work
Looking at a 3D (3-dimensional) photograph can be exciting because it gives you an illusion of depth, with the image appearing like a real version of the object photographed.
One may wonder how such a photograph can be shot and how the images in it appear to be in 3D even though the photograph itself, whether in print form or on slide or on screen, is in a two-dimensional plane with no depth dimension.
To understand how 3D photography (also called stereoscopy) works, it is important to know how this illusion of depth is achieved.
The basic principle of 3D photography
The basic principle of 3D photography lies in simulating the Nature’s way of making us see 3D objects in real life. When we look at an object with both eyes open, our left and the right eyes view the object somewhat differently.
This happens because there is a separation of about 6.5cm between the eyes, which results in the eye optics being different for the left and the right eye. Hence, the two eyes project slightly different images of the object on the retina.
The brain then combines these two images and creates a 3D representation of the object. This is what we view as a real object in three dimensions.
You can comprehend this concept if you try to look at an object first by covering by hand one eye and seeing with the other, then opening this eye and closing the other, and then opening both the eyes together.
Creating the illusion of depth
For obtaining 3D photographic images what we need to do is recreate the two images: one that would have been seen by the left eye and the other that would have been seen by the right eye.
This means you need to shoot two almost identical pictures of the object.Based on this principle, a 3D image can be created even with an ordinary camera simply by clicking two pictures of the object from two different perspectives, ideally 6.5cm apart on a horizontal axis.
This is accomplished by moving the camera sideways, along the horizontal axis, without allowing it to rotate or twist. It is important the object remain stationary during the period between the two exposures.
All that remains to be done then is mounting these two images side by side, about 6.5cm apart, such that the left eye sees only the left image and the right eye only the right. From thereon the brain does the remaining task to create the illusion of a 3D image.
3D imaging of moving objects
This single-camera method described above is suitable only for still photography, not for videography, because the scenario changes in the period between the two exposures. One method that is suitable for still as well as moving objects is using a “twin rig”, which consists of two identical cameras mounted roughly 6.5cm apart on a horizontal bar and interlinked together in such a way that their shutters open at the same time.
Another type of camera that can be used for photographing moving objects is the special stereoscopic camera, which is a single camera having two in-built lenses that are spaced out by about 6.5cm. The stereo images are taken simultaneously. This type of camera is the most suitable one for taking action shots.
New developments in 3D photography
Digital 3D photography is the most exciting development in this field. The basic principle remains the same, but the quality of images is enhanced radically.
For 3D photography digital cameras come either as a single camera mounted on a slide bar or as a single unit of synchronized twin cameras that are custom-wired to click simultaneously. One can also use an ordinary digital camera for 3D photography by clicking the object twice from two different perspectives, as explained earlier.
The latest development is a 3D stereoscopic camera where the 3D image can be viewed directly on its LCD screen, without the need for any special viewing device.
Digital 3D photography becomes even more exciting when combined with computers. Software are now available that allow you to mount these stereo images side-by-side, as required, very easily and accurately for perfect viewing.
Viewing 3D images
Though free-viewing of 3D images is possible with naked eyes, it requires a lot of practice and training of the eyes. Viewing of 3D images becomes much easier by projecting the two stereoscopic images on special optical devices called stereo viewers or stereoscopes. The well-known “View-Master” is one popular example of a stereo viewer.
In a 3D movie, stereo images polarized in mutually perpendicular directions using polarized filters are superimposed and projected onto a silver screen. They are then viewed by wearing specially designed polarizing spectacles.