SMPTE Meeting Presentation

3D shooting with a single digital camera with the use of 3D lenses of the stereoscopic system "Stereo-70"

Alexander Melkumov

Cinema and Photo Research Institute (NIKFI), Leningradskiy prospect 47, Moscow, Russia 125167, info@stereokino.ru.

Written for presentation at the

SMPTE International Conference on Stereoscopic 3D for Media and Entertainment

13 – 14 July, 2010

Abstract.

The Russian stereoscopic system is one of the oldest in the world. This system was used for production of 3D movies for more than 40 years. The important principle of this system is the use of a single camera, single lens and a single film.

The interaxial distance between the left and right lenses should not exceed 30 mm for live 3D shooting if we want to shoot the people and animals without effect of miniaturization and should have a sufficient distance of comfortably reproduced space between the front and background without large parallaxes.

For this reason in the majority of 3D stereoscopic rigs professional digital cameras must be placed not in parallel but at an angle of 90 degrees with the use of a translucent mirror.

The 3D lenses of the Stereo-70 cameras were designed specifically for 3D shooting of the live nature. The small size of optical blocks allows for interaxial distance of 26.4 mm. It is enough to have two 35 mm side by side standard frames on one 65-mm film negative.

The optical axis of each lens can be adjusted to a film when we want to change the distance of the point zero parallax. Remote control of the 3D lens allows cameramen to work without special computing tables.

Recently we have found the way to use the same optical system in digital format with the use of camera "Phantom-65" with a sensor similar to the 65-mm cinema frame.

The choice of single system allows solving the problem of synchronization of the left and right images automatically.

Keywords.
Stereoscopic system, 3D lens, 65-mm film, interaxial distance (basis of the shooting), “Stereo-70”, "Phantom-65", 3D camera.

Introduction

One of the main problems of creating technological systems for 3D shooting of life nature, especially people, is the basis of 3D shooting-the inter axial distance between the left and right lenses which should not exceed the basis of eyesight (65mm) and should have much smaller size, multiple degree to scale increase of the image on the screen. During long-time 3D shootings we came to the conclusion that the more the scale of increase on the screen is, the less the shooting basis should be. For example, if the average coefficient of scale of the image on the screen equals 2.5, the shooting basis should be 65mm/2.5=26mm. Otherwise we will face the problem of miniaturization effect. However, this effect is not a principal cause to stop 3D shooting with the large size of basis of shooting. Spectators can usually gradually adapt to this affect and stop focusing on it if you do not include scenes that were shot with different basis.
The main reason to stop 3D shooting with the basis that equals to or more than the basis of sight is the question of the size of comfortably perceived space. How should it be understood?

One of the key stereo parameter is the “parallax of infinity” which is the positive parallax of the same points of the image which are in infinity. The size of such parallax of infinity on the screen must not exceed 65 mm: Pscreen = Bsight. Otherwise spectators will see the image of background objects in divergention which will cause fatigue and discomfort in viewing a 3D movie.

The second key parameter of 3D shooting is “ramp distance”. It defines the distance from the camera to a virtual plane of zero parallaxes which subsequently should coincide with a plane of the screen in the screen hall. At construction of a composition, objects which will be cut off by frame of the screen should not settle down closer to this distance, otherwise due to the effect of "repellent out action of the screen” the plane of the zero parallaxes psychologically will not be perceived in the plane of the screen. Discrepancies of the plane of the zero parallaxes that were set at shooting with a plane of the screen will cause discomfort and fatigue in spectators during the long viewing of a 3D movie.

The third parameter of 3D shooting is the forward distance to the camera. For static objects which can psychologically be perceived in screen hall space, and are not subject of the wringing out effect of the screen, such distance is equal to half of the ramp distance (these restrictions are not applicable to the dynamical objects which are taking off to the hall). In this case images of such static objects have negative parallax on the screen that is equal to a parallax of infinity. (Fig 1)

Figure 1 illustrated that the role of the positive and negative parallaxes on the screen

Thus, if we want to give to the spectators a comfortable perception of the three-dimensional vision, the range of parallaxes on the screen from the nearest distance to the most distant - infinity should not exceed 130mm. In practice, taking into account physiological resources of the human visual – the affordable excess can be up to 50 % of the above described sizes. And in some occasions the parallax of infinity can be up to 90 mm.

The above mentioned parameters of 3D shooting are interdependent from a focal length of an objective and the basis of 3D shooting. This interdependence is expressed by the formula:

Where L ramp - a ramp distance, B – interaxial distance between left and right lenses, F - a focal length of an objective, H - coefficient of proportional transfer of space, equal 1, and P ? the maximal size of a parallax of the image on a film or a sensor of the camera, which will be 65mm on the screen with the projective increase

Each 3D lens under the certain basis has the main distance ramp under which the shooting is conducted under proportional - spatial parities when the same points of objects of infinity have the parallax equals to 65mm on the screen. In a case of the reduction of a distance of a ramp aside, objects of infinity will have the parallaxes considerably exceeding 65mm; therefore a scene composition should be limited by a background, located at the final distance that is determined by the formula:

If the background located at the final distance will have the parallax equals to infinity on the screen, the proportionality of space transfer will be broken. The Index Í designated the hypertrophy of space transfer is defined by the formula:

With the help of these formulas we produced the interactive table of stereo parameters. This table shows, how the shooting basis impacts the size of the range of comfortably perceived space (Fig.1 and 2).

Tables of the stereparameteres

Figure 2 illustrated, that shooting with interaxial distance 26 mm

Figure 3 illustrated that shooting with interaxial distance 65 mm

For example, in a case of a 3D lens of 35mm, at shooting basis of 65ìì we have restrictions from 11m to indefinitely, and the shooting with basis of 26ìì, this range will be essentially larger - from 4.5mm to indefinitely. Approaching the actor at the shorter distance, for example 3 meters, the restriction of space at 26mm will be from 3 up to 9 meters, and at base 65mm - from 3 up to 4 meters.

What is it “Stereo-70”?

The Russian stereoscopic system “Stereo-70” is one of the oldest in the world. This system was used in production of 3D movies for more than 40 years. It was designed for a 70mm cinema that is why it name is “Stereo-70”. The important principle of this system is using a single camera, single lens and a single film.

Two frames of a 35 mm format locate on the single 70mm film (Fig.4). In this case the interaxial distance between frames is 26,4mm that meets the requirements of shooting of the alive model described above.

Figure 4 illustrated that two side by side 35-mm image on single 70-mm film

Optical blocks of the small size could be placed on the interaxial distance of 24.4-26.4 mm (Fig.5). The blocks with built iris are placed in a special design which allows to remote control them synchronously.

Figure 5 illustrated that small size optical blocs

Optical blocks are located strictly in parallel, but the mechanism has been developed, allowing shifting them concerning the centers of the frames in a range of 2mm that allows a plane of zero parallaxes on various distances, down to infinity. In this case there is an “imaginary convergence” by lateral optical axes of the lenses (Fig.6).

Figure 6 illustrated that the imaginary convergence
1- plane of the film, 2 -plane of the focal lens, 3 - plane of the screen
B1 – interaxial distance between frames, B2 – interaxial distance between lenses

Thus, two optical blocks consolidated in a uniform frame will form a uniform 3D lens, having the remote control of the focus, iris and imaginary convergence. The cameraman has a complete set of seven 3D lenses: 23mm, 28mm, 32mm, 35mm, 40mm, 75mm and 100mm (Fig.7).

Figure 7 illustrated that line 3D lenses of the “Stereo-70”

An interaxial distance may be changed by optical attachments could allow to increase the basis up to 110 mm, and also to reduce it up to 15 mm. Changing of basis of shooting can be done discretely (Fig.8).

Figure 8 illustrated that optical attachment for changing interaxial distance of the 3D lens

Basic nozzles can be used with objectives, starting with the focus of 40mm, therefore now is developed short focal lens with optical blocks by a principle of a periscope when entrance interaxial distance exceeds target twice (Fig 9).

Figure 9 illustrated that 3D lens with large interaxial distance

The main difference between a 3D camera and the regular camera similar to 70mm format is the presence of a binocular view finder (Fig. 10).

The cameraman can directly observe the three dimensional image and a convergence of crosses visually to expose lenses on a distance of a zero parallax necessary for the cameraman. Frames of the film channel, the partition, established after optical blocks in the camera allows to have precise borders of the left and right frame of stereopair, and to avoid mutual imposing of images of the left and right foreshortenings.

Figure 10 illustrated that binocular view finder for 3D camera

3D cameras have various updating:

Type of Camera Drive System Frame Rate Reverse Filming Magazine Viewfinder Weight
"TRANSFORMER-65"

Hand-held & Steadicam

DC motor 12v external 8;12;16 fps
24;26;32 fps
Quartz-timed
No 245ft – 5 pcs
400ft – 2 pcs
500ft – 2pcs
Binocular viewfinder &
TV assist
8-10 kg

(18-22 lbs)

"SHOULDER-65"

Shoulder-mounted

DC motor 16v internal 1 – 50; manual 24; 25; 30
Quartz-timed
Yes 450ft – 5 pcs
500ft – 2 pcs
Rotary binocular viewfinder 15-25 kg

(33-55 lbs)

"HAND-65"

Hand-held

DC motor 12v external 1; 2; 4; 8;
12; 16; 24;
26; 32 fps
Quartz-timed
No 245ft – 5 pcs
400ft – 2 pcs
Binocular viewfinder 7-9 kg

(15-20 lbs)

"SPEED-65"

High-speed & single frame shooting

DC motor 30v external 1 to 72 fps Yes 1,000ft – 4 pcs Binocular viewfinder 25 kg

(55 lbs)

"BOX-65"

Underwater shooting

DC motor 16v internal 24 fps No 245ft – 5 pcs TV control 30 kg

(66 lbs)

General Specifications all models

Purpose

Shooting of feature and documentary films in 3D

Stereopair Type

Horizontal "SIDE BY SIDE"

Frame Size

26 õ 18.2 mm

Film Types

65 mm Black & White or Color.

Pull-Down and Pin-Registration

Dual forced

Registration Pin Vertical Instability of the Image

0.01mm

Shutter

150°

Noise level

45 dB

"TRANSFORMER 65"

“SHOLDER 65”



“HAND-65”

SPEED-65"

Everyone frame of the stereopare of 65-mm film-negative has information capacity at least 4K. The aspect ratio of the frame 3:4, is right for the Large Format for the Giant screen.

Under the technology "Stereo - 70", since 1967, it has been shot more than 30 3D films. System «Stereo - 70 " and its 3D lenses passed some stages of modernization. Last development of cameras has been carried out in the Moscow cinema equipment design bureau (MKBK) in 1995-1997. In 2009 under our technical project, the company «Optics Elites» had been developed new optical blocks in view of their application for digital cameras (Fig 11).

Using system «Stereo-70» in digital technology

The System «Stereo - 70» has been developed and created during an epoch of development of 70-mm cinema which now has no commercial distributions and which was ended by the end of 80th. of 20 century. Therefore, the production of 3D movies under this technology has been suspended in the beginning of 90th. The last attempt to produce the 3D movie under the Stereo – 70 cameras, has taken place in July 2009 in Spain during national holiday “San Fermin”, where took place the shooting of 3D trailer of the movie -“Running with Bulls ” – the producer - Chris Cary, the director - Aubrey Powell. The production company «San Fermin» has chosen the film technology as the movie should be filmed on the Large Format for Giant screens.

With the arrival of digital technologies the basic direction of our activity has been focused on the development of the technologies, allowing using the scientific potential of the system «Stereo - 70" in the creation of 3D movie without using the 70-mm film. We had the experience of the production of the 3D stop-motion animation of the system «Stereo - 70" since 70-years of the last century. But after stopping the production of 70mm format, 3D stop-motion animation began the most vulnerable in this question. Therefore, our first step was creation the technology for 3D shooting stop motion animation by a single still digital camera for the Giant screen (Authors: Alexander Melkumov and Sergey Rozhkov). The first presentation of this technology took place at the Galveston GSCA Conference in September 2006. The first 3D movie shot under this technology was "Scarecrow", developed together with the Estonian studio "NUKU-FILM". It was shown at the Vancouver GSCA conference in Canada in 2007. Now the full length film « Lisa Limonene » is being produced by the same studio.

Our next step was the creation of a 3D system based on two Sony HDV cameras. These small-size cameras allow to have the shooting basis to be equal of 68ìì and their view-finders play a role of a binocular view finder. For the reduction of the shooting basis that is necessary to the comfortable shooting, MKBK has developed a special prismatic nozzle that could reduce the shooting basis in 2 times to 34ìì (Fig. 12).

Figure 12 illustrated that 3D rig with prism attachment for two HDV cameras

In these two cases we adhered to principles of calculation of stereoparameters on system «Stereo – 70», and step by step came nearer to idea of creation of the specialized digital 3D camera which would not concede on convenience of work with film camera. We understood, that for use of «Stereo - 70» lenses it will be necessary to have the digital camera, at least, with dual sensor equal 35-mm format, or with single sensor as 70-mm cinema standard.

One of models of digital camera of the company «Vision Research » widely known as "Phantom", has received a prefix 65, because of the sizes of the sensor used in it corresponding to the size of the 65-mm film.

Subsequently MKBK made the big work on adaptation "Stereo - 70" lenses to "Phantom-65". It was insufficiently simple to design a lens mount (Fig. 13), it was necessary to create between a lens and a sensor the special shaft for division of the light streams falling from the right and left optical blocks (Fig.14).

Figure 13 illustrated that 3D lens with lens mount of the Phantom-65

Figure 14 illustrated that shaft for division of the light streams

The test-shootings with "Stereo - 70" lenses took place in April 2010, and the production of a full-length motion pictures under this technology is under consideration. However, a high-grade digital 3D camera similar to "Stereos - 70" camera does not have a binocular view finder for a cameramen. Currently, the control is conducted via the monitor with images from two stereopairs. The important stage in the preservation of the «Stereo - 70" system became the creation of the new generation 3D lenses in which the mechanical part of the remote control is replaced by the optical electronic block (Fig. 15).

Figure 15 illustrated that 3D lens «ZEPAR»

The focus, iris and imaginary convergence can be wirelessly controlled. The borders of the comfortably reproduced space determined by the "Stereo - 70" system can be programmed in the device. They are automatically shown on the display during the installation of the zero parallaxes distance by the cameramen.

The 3D digital camera«Phantom-Stereo-70”

«Phantom-65» with Stereo-70 lens (NIKFI) «Phantom-65» with “ZEPAR” lens (MKBK)

Conclusion

“To doubt that stereoscopic cinema has its tomorrow is also naive, how to doubt whether there will be tomorrow at all!" –a quote from the article «About stereoscopic cinema» by Russian director Sergey Ejzenshtejn which was written in 1947 under the impression of the first Soviet 3D movie "Robinson Cruise".

More than 60 years passed, a new area of 3D has come. But we are not ready for it. We do not have cameras to produce 3D movies that would be the same level as a traditional movie camera. The use of two camera systems for 3D is as archaic as we would try to use today a three black-white film for a color movie instead of a multilayered color film.

The «Stereo - 70" system with the principle of single camera, single lens and single film, is unique in its optical part. The same advantages of Stereo-70 can be used at designing the digital camera for 3D shooting.

The current approach of the adaptation of «Stere-70» 3D lenses to «Phantom-65» show us what kind should be modern 3D camera.

The Stereo - 70 film camera with the two 35-mm frames stereopairs has the 4K information capacity but each sensor of “Phantom-65 " with the joint capacity of 4Ê has only 2Ê each foreshortening. We hope that the companies developing digital cameras will fill the necessity of designing the digital cameras with the sensor 8K with size that will be equal to the 65-mm cinema standard for production of high-grade and quality 3D movies.

Video SMPTE Conference

Trailer "The Best Film in 3D" (was shot by "Phantom-65&Stereo-70")

Bibliography:

Journal Articles

A.S. Melkumov, “The new Renaissance of the stereoscopic cinema ”, Technical equipment and technology of cinema, ¹1, Moscow 2006

A.S. Melkumov, “3D shooting stop motion animation with one still digital camera”, Technical equipment and technology of cinema, ¹3, Moscow 2006

A.S. Melkumov, “3D shooting in digital format”, The Word of Technical Equipment of Cinema”, ¹ 4, Moscow 2008

A.S. Melkumov, “3D cameras for stereoscopic cinema”, Technical equipment and technology of cinema, ¹1, Moscow 2009

Articles Published in Proceedings:

A.G. Boltyanskiy, N.A. Ovsyanikova “Geometrical laws of shooting and projection of 3D films”, Proc. NIKFI, Moscow 1959, the edition 31

Books:

N.A. Valyus “Stereoscopic cinema”, Academy of sciences of the USSR, Moscow 1962

N.A. Valyus “Stereokino”, Moscow 1974

Chapter in a Book

S.M. Eisenstein. “About Stereoscopic cinema”, The Penguin Film Revue, ¹ 8, Penguin Books, London, 1949