3D-Rig

With the help of a 3D rigs two cameras are connected to a 3D camera system to capture stereoscopic 3D movies and photos.

  • 3.1 Structure
  • 3.2 Field of application
  • 3.3 Advantages
  • 3.4 disadvantages

Background

To produce a stereoscopic depth illusion, two images to be shown with a horizontal parallax at the same time, one for each eye. These can be recorded simultaneously with two either sequentially by a camera or. If moving objects are captured, it is important that the images are taken at exactly the same time. Depending on the speed of the object can thereby lead to errors in the representation of depth tiniest asynchronicities. Therefore, in photography and especially in film, usually two cameras are used.

In addition, care must be taken that the two cameras are geometrically correctly aligned. Even minimal deviations from a parallel alignment of the two camera axes lead each other to a false impression of the room, or to the fact that the images produced nausea or headache cause. The challenge for a 3D rig, then, is that this two cameras are connected together so that they can be aligned in all axes, but this alignment is maintained even in movement. For the production of 3D films also the horizontal distance of the cameras with each other during recording should be changed by means of remote control, so as to address different photographic situations.

Basically there are two types of 3D rigs, side-by - side rigs and Spiegelrigs.

Side-By -Side Rig

Construction

The easiest way to capture a 3D image by placing two cameras side by side. The optical axes are aligned either parallel or can be converged so that they cross each other at a predetermined distance. In some side-by - side rigs, the cameras are rigidly connected. In addition to the rigs from hobbyists to this principle is for example the GoPro 3D rig and all 3D camcorders, since it is comparatively easy to implement. But Professional Side -by - side rigs offer the possibility to adjust the distance between the camera axes. It is important that the correct geometric orientation is then also obtained when the cameras are moved.

Area of ​​application

A Side-By -Side Rig is great for long shots such as landscapes or supervisors of sports broadcasts. Close-ups however, they are unsuitable, since this the distance between the camera axes must be less than the diameter of even small lenses.

Benefits

Side -by - side rigs are relatively easy to build and therefore cheap .. In addition, they often provide a greater maximum distance between the cameras to each other as Spiegelrigs. This can then be measured to achieve a miniaturization effect or Liliputismus and to make it look like a model landscape itself mountain ranges.

Disadvantages

Side -by - side rigs can not be used for close-ups, as the smallest possible distance between the camera axes is limited by the size of the lenses. Close-ups but this distance may sometimes not be larger than a few millimeters. Therefore be used in scenic filming usually Spiegelrigs.

Mirror rig

Construction

In a mirror rig, both cameras are on a semi-transparent mirror, called a beam splitter aligned. This reflects fifty percent of the incident light. The other fifty percent will be transmitted. A camera films the mirror image, the other looks through the mirror. Since the cameras are thus physically separated from each other, they can be located on the same optical axis. In the mirror image of the cameras overlap and can seemingly merge into one. In this case, the recorded image is the same. Based on them can now, any distance between the two optical axes set and thus the depth of the image are chosen freely.

Area of ​​application

The fact that even very small interaxial distances are possible, a broad spectrum can be converted to setting sizes. Characterized the mirror rig for use in scenic film is most suitable.

Benefits

By Spiegelrigs will tell with classic film style means possible. Also offers the possibility to place the optical axes of the two cameras exactly one above the other, the advantage that the Videoausspielungen for the geometrical alignment of the cameras can be used.

Disadvantages

The mirror is another optical element, which must be precisely manufactured and is prone to dust and scattered light, and other debris. The cost of high-quality beam splitter driving up the price of a Spiegelrigs in the air. In addition, the distribution of light for each camera causes a loss of brightness of a diaphragm. Levels of lower quality often cause a different color behavior of the two images, which must be corrected consuming in post-production. In addition, there may be problems if the mirror with light filtering depending on its polarization. This occurs especially in reflective materials, such as metal, leaves and rain-soaked roads.

In some Spiegelrigs only one of the two cameras can be moved. These have the disadvantage that they bring with Steadycam shots the entire system off balance if the distance between the cameras is changed each other. To avoid this there is Spiegelrigs in which both cameras are automatically moved simultaneously, so that the balance is maintained.

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