3D DIGITAL SHOOTING

WITH SMALL INTERAXIAL DISTANCE

There is a set of technological decisions for digital 3D shooting which can be divided into two groups under the basic optical circuit. It is shooting on perpendicular axes through a translucent mirror or the shooting cameras located side by side on parallel or conversional axes. In the first case, these systems, as a rule, are bulky and have bad ergonomics. In the second - the system has the big basis of shooting (inrearaxial distance between cameras glasses), with natural dimensions of cameras.

The size of basis of shooting influences distance between near and far borders of a removed stage. Similarly to depth of sharply represented space in a photo, this is the depth of space which can be comfortably perceived from the screen. The more the size of basis of shooting is, the less such depth is, the farther from the camera the forward border of reproduced space should be situated, if the composition has the big extention.

One of the ordinary errors is that the basis of shooting should correspond to the average the view basis - 65 mm. It would correspond to the truth if we observed images of objects on the screen in their real scales. Actually on a screen we notice images with the increased scale. In this case the basis of shooting equal to view basis will be considered as the increased basis. The increased basis of shooting creates effect of miniaturization of the image. It has empirically been determined: the more the scale of represented objects concerning real, the less basis of shooting must be. An indispensable condition for 3D shooting people, especially, their average and close ups, is two-multiple reduction of size of basis of shooting concerning size of the average view basis (65 mm) , at least. Otherwise we shall observe effect of miniaturization of people on the screen.

Parameters of 3D shootings, such as: the basis of shooting, a focal length, distance up to a plane of zero parallaxes, a lobby and far border of a composition of the seance, factor of a projection - are interconnected by mathematical formulas on the basis of which the interactive table developed by laboratory NIKFI on which the operator can calculate necessary sizes of parameters for each certain composition is designed.

Proceeding from the analysis of all previous systems of 3D shooting video and the requirements of stereo schedules, in a Russian Cinema and Photo Research Institute (NIKFI) the laboratory of a stereokino and new kinds of film-shows develops the technology in 3D shooting in digital HD TV format and the subsequent formatting of the shooting stock for a digital projection in 2Ê.

After strict expert examination and testing as base model digital camera Sony HDR-HC1E of format HD TV has been chosen. In the market of the videocameras, this was unique model, from having port of external synchronization which dimensions allowed to design an optical attachment for double reduction of basis of shooting. Simultaneously, so small dimensions of cameras allow to place them on so close distance, that the interaxial distance of video view founder practically equals to view basis of the people that transforms them into a binocular view founder and allows the operator to observe the direct 3D image at shooting. Now the model is taken off from manufacture, but on change to it there has come new model Sony HVR-A1U , absolutely identical dimensions and positioned as the camera of a professional class.

Synchronization of cameras occurs through Long-port by the external synchronizer. The control panel allows to include and switch off synchronously cameras, to include and switch off record, to operate zoom and sharpness. The multilevel interface of the display informs the operator on the set forth above control modes by synchronization and shows size unsynchronization in milliseconds.

Specially developed optical attachment discretely changes basis of shooting with 68 up to 34 mm. The reduced basis of shooting allows to conduct shooting without effect of miniaturization in a wide range of focal lengths and even to use the zoom.

The image observable in a screenhall settles down in two zones - Behind the screen and in front of the screen. The plane which divides the spatial image on these zones and which passes through a plane of the screen, refers to as a plane of a stage, or a plane of zero parallaxes because the same points of the image perceived in this plane are merged in one image and have a zero parallax. The same points of the image of the object perceived in behind screen pace have a positive parallax, and the same points of the image perceived in front screen space will have a negative parallax.

As in our case shooting is conducted on parallel axes, to points of a zero parallax there correspond to the images of the objects located in infinity. It means, that the image will have a negative parallax and will not reach in behind screen space. It will not correspond to that spatial picture which we observed at shooting.

Therefore the finished shooting image should be subjected to formatting on points of a zero parallax. Formatting occurs in program Adobe AfterEffect. In each finished shooting composition the distance on which there passes an imagined plane of a stage then the image of the left foreshortening is shifted concerning the image of the right foreshortening so is defined what the same points located on a distance of a plane of a stage were combined. After formatting we have two images of dynamical stereopair, one of which can be transferred to the director for installation, and the second will be automatically substituted in the project of the assembly program after end of installation.

The complex for 3D digital shooting has passed field tests to days of the Cannes festival in May, 2008 in shootings of opening of Russian House, a concert of group " TATU ", was shot the movie "New York in 3D", Musical festival "Spasskaya Bashny".

Authors of the project:
Sergey Rozhkov
Alexander Melkumov