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D-Cinema, E-Cinema and wide screen video projectors The first in Russia the non-film presentation of motion-picture film of Sergey Nikonenko “And in the morning they have woken up…” was hold in Khabarovsk relatively recently. It is the movie film that was transferred directly to cinema through the channel of satellite communication. By the program “National screen” the re-equipment of old cinemas with installation on their roofs the special antennas in 34 regions of Primorski Area is stipulated. So it is planned to capture that part of the film-market which the film cinematography does not use, — the most remote out-of-the-way place. Translation of one film costs 400 $. “Arguments and facts” newspaper, № 7, 2004. The first demonstration of digital cinema in Europe with distribution of film copies in cinemas through channels of a satellite communication was held within the framework of European project CyberCinema by autumn 1998 on festival of children’s films. Transmission was carried out by four multiplexed streams MPEG-2 and was received by Deutsche Telekom stations. At the same time, though since then has passed almost 6 years, and digital revolution in a motion-picture which count the greatest from time of appearing of the audio cinema, has already taken place, in global scale the digital films and cinemas on general background are almost imperceptible. The first in Russia demonstration of the digital cinema prototype was held at exhibition TRBE’2000 during realization of the seminar “Digital cinema and the High Definition TV”, organized by “Era” (Zhukovsky) and National Association of TV Broadcasters (NAT). Further actions with presentations of the real equipment have followed. At the international conference “E-Cinema. Production and distribution” (28.11.02) which was organized by NIKFI, in concert hall of Moscow hotel “Cosmos” by “Era” company and TKT magazine was demonstrated the equipment functioning on the 15-meter screen. The projector JVC DLA-QX1 with resolution 2048×1536, the disk HD-recorder, the digital VTRs D-VHS and HDCAM were used. Participants of conference were acquainted with the standard 1080/24p for high definition TV systems of (HDTV) and results of the comparative analysis of quality indicators of a digital and film cinema. The basic outputs by this conference were as follows. The first, by all parameters, except for perceptibility of the finest picture components, the modern digital cinema does not concede to film and is favorable at stages of production and distribution of movies; the second, the most perspective format of HDTV video recording for small and medium cinema halls is D-VHS by JVC Professional Products. On one cartridge of this format it is possible to write down the four-hour program of a HDTV with MPEG-2 compression and with high quality. Important argument for this format is low cost of the media. February 12, 2003, within the framework of an exhibition of cable and satellite television, broadband telecommunications CSTB-2003 the demonstration of digital movies in cinema halls of Moscow multiplex “Formula of Cinema” was carried out. Here the “Era” company have showed a version of compact equipment for halls with the 8-meter screen (projector DLA-M2000, 1365×1024, 2000 ANSI-lumen, weight 15.6 kg together with VTR D-VHS), and “NevaFilm” company (Saint Petersburg) have showed the project of system integration of digital cinema with DLP Cinema technology. This project maintained by companies Barco Digital Cinema (Belgium), Kinoton GMBH (Germany) and EVS Digital Cinema (Belgium), was developed by division “NevaFilm Digital”, created for practical realization of digital cinema systems in Russia. Its presentation was held in the 272-seat hall with screen 10.4×4.4 m and projection distance of 19.4 m. As a source of the information the floor DLP-projector Barco D-Cine Premiere DP 50 and digital server EVC CineStore were used. Depending to capacity of a xenon lamp used (2, 3, 5 or 7 kW), the light flux from this projector is sufficient for screens by width up to 20 meters. Resolution is equal to 1280×1024. The similar set with desktop projector DP 30 (lamp 2 kW, 85 kg, the screen up to 10 m) was installed at the Moscow cinema “Kinosphere”. Here December, 25, 2003 for the first time in Russia, simultaneously with all-Russian cinema-theatrical distribution, the digital presentation of Disney’s movie “In search of Nemo” is began, but it presentation have been continued not for long. Multiplex “Kinosphere” is part of popular entertainment cinema-complex TC Ramstore-city together with the first cinema in Russia Nescafe-IMAX, which was opened by BFC Cinema Company. It was found, that profiling one cinema hall of multiplex for presentation of digital video recordings of motion-picture films while does not justify itself, as while it is not enough (about 150) films of high definition is produced for demonstration at digital cinemas. For wide introduction of digital cinema, the state support and improvement of the business models providing benefits for each link of the movie production, distribution and film service system is necessary. There are also other problems. VideopiracyIntroduction of digital technologies demands new decisions in the field of protection of copyrights. According to the American association of cinema producers MPAA the annual losses of the film-industry from a piracy exceed 2 billion dollars. Therefore today on the next coil of actuality the immemorial problem “the lock and a master key” is came out. The conventional decisions regarding protection of digital films from the non-authorized access are not present yet, and it does not suit the Hollywood. We shall remind readers, that as was found out, 7 years back the decision of this problem was inefficient, and its coordination with Hollywood as a minimum for half-year has detained the approach of DVD era. Today the significance of a presence of an effective protection against a piracy is much higher, as it is necessary to protect the digital records with picture quality, almost indistinguishable from the film original that is much higher, than on DVD. As attempts of piracy penetration may be undertaken at any stage of manufacturing of the digital version of a motion-picture film, the systems of encryption of digital content, which are decoded only in projectors after receiving by them the distributive password on satellite TV channels directly before a cinema show, are created. Methods of putting on digital copies of the special symbols (watermarks) invisible to spectators, but making impossible a satisfactory re-shooting of motion-picture film by camcorder directly from the screen of a cinema are improved. D-Cinema and E-CinemaGlobal standardization of digital cinematography is finished. Work of the leading teams of ITU, SMPTE DC28 and MPEG in this direction is in progress by Digital Cinema Initiatives (DCI) organization, created by seven leading film studios from Hollywood for coordination in the area of digital cinema and interests’ protection of creators of the American movies. D-Cinema is understood as the picture with decomposition to 1080 lines with 1920 elements in each of them (1080×1920) and higher, which in long-term prospect will replace the film media by digital production. D-Cinema means the best presentation (an electronic projection) of this production and its protection against video piracy at all technological stages. While all Hollywood studios support D-Cinema only with micro-mirror projectors of category DLP Cinema from American corporation Texas Instruments. Under license agreements the DLP Cinema projectors are produced also by Barco, Christie and NEC Viewtechnology. One of serious players in D-Cinema area is airline company Boeing which is successfully strengthened itself provider positions for digital cinemas. This company is already ensured more than 10000 cinema shows through transmission of motion-picture films in cinemas of USA and Great Britain under satellite communication channels. The European Forum of digital cinema (European Digital Cinema Forum — EDCF) supports the D-Cinema platform on integration and cultural reasons (strengthening of the European cinematography and its revival in small cities). E-Cinema with HDTV resolution (1920×1080) and less takes into account interests of wide layers of the population in high quality of not only electronic cinema, but also “alive” translations of the alternative contents, for example, theatrical plays, musicals, sports competitions and education programs. It is supposed the projector application on the basis of alternative DLP Cinema technology. All European and American cinema networks are actively used the E-Cinema systems for presentation of the advertising, alternative programs and business-applications as in addition to existing projection from films though E-Cinema does not guarantee the protection against a piracy and does not meet the requirements of the motion-picture film creators. The basic requirements to video projectors for E-Cinema and D-Cinema applications are shown in the table.
From this table is followed, that in the field of the servers creation for D-Cinema some technologies are competed till now. It means, that digital films are created in formats incompatible among themselves that is unprofitable for film studios and cinemas. It is now observed that pushing out from the market of local formats for the benefit of standard formats SMPTE (MPEG, Motion JPEG), but DCI is intended to standardize its own system. It is possible, that it will be appeared the system offered by Sony which advanced in Hollywood by studio Sony Pictures (Columbia/TriStar). In such a way, the standardization was slowed down, and the new D-Cinema films shown in 2003, in comparison with 2002, are less. In Europe is believed, that D-Cinema is impossible without Hollywood which is presenting more motion-picture films, than all film studios of other countries altogether, and consider E-Cinema as an opportunity of demonstration of the alternative content, that is not the Hollywood films. The quality scale of an electronic projection begins with minimal, provided with data-transfer rate 25 Mbit/sec (DV, DVB, DVD) and extend up to the Digital-Cinema-Master level with picture decomposition to 2500 lines by 5000 elements in each. E-Cinema applications occupy the bottom part of a scale up to HD-DVD and HDTV level, that is between standard and HDTV-width of a frequency band, and D-Cinema its upper part. Media and hardware sources of the informationThe master-file of the film scanned with high resolution occupies the volume more than 10 TB. In cinemas the files are entered only in compressed state after digital correction of luminance, color palette of the picture and introduction of digital phonograms. Depending on used algorithm the compression degree may be various, for example, from 1:20 till 1:30 MPEG+, that without visible defects allows to compress the file with a two-hour motion-picture film up to 40…50 GB. Some methods of delivery of digital films and other content in a cinema are applied. The most widespread are the packets of 8…12 standard DVDs, loaded in the cinema server, D-VHS videocassettes, delivery through TV channels, cable and fiber-optic communication lines. HD DVDAs delivery and use of DVD packets for domestic cinema are problematic, the big hopes are assigned on high-resolution DVD, recorded by the blue laser. The international organization in the area of information technology DVD-forum in this year is planned to approve the uniform standard for HD-DVD. Generally in this area two development compete on this field: BDF (Blue-ray Disc Founders), advanced by Matsushita, Philips, Sony under support of Hitachi, JVC, LG, Mitsubishi, Samsung, Pioneer and Thomson, and AOD (Advanced Optical Disc) as well, offered by NEC and Toshiba under support of four duplicating companies, including Hollywood cinema company Warner Brothers. The standard BDF was developed earlier; the Blue ray disks and players are already produced. The standard AOD officially submitted for the approve by DVD-forum at the last summer, unlike BDF standard, is realized at maximal similarity of technological processes of manufacturing of new and already existing disks, that is almost without expenses for the production preparation. It is rather essential, that the AOD disk, unlike the Blue-ray disk, has reverse compatibility with existing DVDs and does not demand any protective cartridge. But AOD as the uniform standard for HD-DVD, is not approved yet, as the majority of the administrative board members of DVD-forum are supporters of BDF. Many observers consider the decision accepted by DVD-forum as politicized, connected with that it authority was captured by Sony/Columbia TriStar group. If it so the future may be any, from the approval of BDF standard from a tacit consent of AOD supporters to dissolution of DVD-forum by summer of this year because of expiration of 10-years authorized period of its existence. In the meantime in France, Germany and Great Britain the production of HD DVD with resolution 1440×816 and data compression by algorithm Microsoft Windows Media 9 (WM9) is begun. For the first time this algorithm was demonstrated by Microsoft on IBC-2002. WM9 Video Pro provides the storage of full-length motion-picture film with six-channel phonogram 5.1 on one standard DVD at resolution up to 1080p, that is approximately in 6 times higher than resolution of typical DVDs. As for SD/HD server with a player of disk media the DVD/HDD-recorder would be suitable for it, for example, Panasonic DMR-E100 on condition that it will support the playback of HD DVD. So with a choice of such server it is better to wait, while the confusing situation with HD DVD will not clear up. Delivery of digital content through satellite TV channelsDigital platform WM9 is used also in terrestrial and satellite HDTV broadcasting as in comparison with MPEG-2 and MPEG-4 provides the best video and audio quality at higher compression level. The service “Video on demand” have begun to work in 2002 under Hollywood support, and now for inhabitants of USA more than 200 motion-picture films are available. The largest European operator of satellite broadcasting the SES Astra company will soon start the regular broadcasting on WM9 platform within the framework of Euro1080 project through the HDTV channel through satellite Astra 4. In Germany the network of distribution E-Cinema through the satellite at HD-level with the centre in Leipzig with weekly change the films is expanded. The national operator of satellite communication RSCC Copmany has the largest Russian group from ten geostationary satellites of “Horizon” series, “Ekran-M” (“Screen-M”) and “Express-A”. This year the launch of five satellites of “Express-A” series is planned. One of perspective directions of work of the enterprise is creation of multiservice networks on the basis of VSAT-technologies for delivery to spectators of the TV and other programs with bit rate 2…45 Mbit/sec. The subscriber receiving terminal consists of the external unit with antenna by 1.2 m in diameter (Ku-range) and a receiver. Use of digital satellite TV for delivery of E-Cinema programs is convenient and favourable because of the following:
VTRsIf waiting of standardization of HD DVD and occurrence of players for them are tired, it is laziness to be equipped by “plate”, satellite TV receiver and to master the work with it, and it is required to realize at the minimal expenses a domestic cinema right now, it is necessary to pay attention to high-quality VTRs of D-VHS format. The best of them, for example JVC HM-D30000, are by HS category and are capable to work with bit rates up to 28.2 Mbit/sec in 1080/24p standard with a multichannel phonogram and provide 3.5 hours of recording on one cartridge with almost cinema quality of the color image. The maximal speed of bit rate at D-VHS VTRs of STD category is 14.1 Mbit/sec that it is twice less, than of HS category, but three times more, than of DVD (4.7 Mbit/sec). Therefore they provide obviously better quality, than DVD players as because of lack of information capacity of DVD the motion-picture films are recorded on them with compression. The D-VHS VTRs normally may work and in analog S-VHS/VHS formats and on several speeds of the tape movement. In the digital HS mode this speed is equal to standard SP speed for analog record system NTSC, that is 33.35 mm/sec, and twice smaller in the STD mode. The speeds slowed down for digital video recording in 2, 3, 5 and 7 times smaller than STD, are designated such as LS2, LS3, LS5 and LS7. Cartridges for digital videorecording have the appropriate trade mark and the designation, for example, DF-420, where the figure designates the playback duration in minutes. The information capacity of such cartridge is 44 GB as in contrast of 4.7 GB of DVD. Appearance of VTR D-VHS JVC HM-DR10000EU (468×145×369 mm, 8 kg) of STD category with the closed front panel is shown on figure. It is the universal VTR, capable to work with various tape speed. For digital record it is D-VHS PAL (STD and LS3 speeds), and for analog recording — S-VHS PAL, VHS PAL/MESECAM (SP and LP speeds) and playback NTSC on PAL TV sets (SP and EP speeds). The advantage of DR10000 is the opportunity of copying of PAL analog video with it conversion in digital which allows to keep quality of the image. Videocassettes D-VHS with digital video may be used as the keepers of film library in E-cinema theatre. However, it is considered, that duration of reliable storage of video records on magnetic tape is about 10 years because of natural wearing processes and ageing, as in contrast to DVD where this duration is more on the order. But in HS mode on one cartridge DF-420 is possible to record 3.5 hours of video with the highest quality of the color image inaccessible even for DVD in the foreseeable future, or 14 hours in LS2 mode with quality of typical DVDs. As follows from the following table, in LS3 mode the digital D-VHS recording gives the same picture quality as VHS VTRs (240 TV lines), and even smaller speeds in LS5 and LS7 modes are suitable for copying of highly compressed videoclips only.
Opportunities of recording by D-VHS VTRs of the uncompressed information on D-Theater platform of JVC Company providing the protection against piracy copying, were determinatives for producing of digital records of films by Hollywood studios. Some of them let out copies of the films on DVD and D-VHS. Formats of projection and projected film imagesThe international legislation on protection of copyrights demands, that at display of videomaterials their author’s formats were kept. The most of all formatted versions of the image have arisen in development of a motion-picture. Basically in present those from them which have been applied a 35-mm film for shooting are kept. For ratio of height of the shot frames 1:1.33 and 1:1.37 (approximately 3:4) it is typical silent and sound cinema, and 1.66:1 and 1.85:1 are wide-screen cinema with letter-box frame and 1:2.35 (CinemaScope) is wide-screen cinema with the anamorphic frame. As is known, that wide-screen images of motion-picture films with letter-box frame are formed by formatted sampling 1:1.66 or 1:1.85 with the help of the appropriate restrictive frames (cachet) and occupy a part of the area of general 35-mm frame. In contrast with them the images of CinemaScope system occupy all useful area of the film frame and are shoot with horizontal compression. For restoration of initial proportions of the shot objects the images CinemaScope under projection extend in horizontal direction twice with the help of a special lens or optical anamorphote component (extension or accessory) added to the basic lens of projector. The screen formats 1:1.33 (3:4) and 1:1.78 (9:16) for standard (SD) and high (HD) definition TV have also received are wide delivered. As shown at figure, the format 1:1.78 occupies the central place among the listed versions. It is the basic for E-cinema and authoring of DVD-versions of wide-screen motion-picture films. Luminance of the screen image, its size and light beam from projectorScreen luminance is defined at projection of a white field as the ratio of the light intensity, radiated by the screen in a sighted direction, to its area seen from this direction. A unit of measurements of light intensity in the SI system is candela (cd), luminance — cd/m², named also neat (nt), and a light flux — lumen (lm). Among experts in film-engineering till now are popular the following stand-alone units of luminance: lambert (1L = 104/π cd/m²) and foot-lambert (lm/ft², 1 fL = 3.426 cd/m²). So, in America for screen luminance (into blacked out halls) the specification 16 fL (55 cd/m², being the nominal rate for film projectors according to the SMPTE standard) is valid. As luminance of a screen is measured at absence of a film in the projector gate, and because of absorption of light the visible part of light beam is loosed, for the screens with the video projectors in E-cinemas the specification 12 fL (41 cd/m² is accepted by SMPTE. As non-standard unit of measurement and calculation of luminance of reflecting surface the apostilb is also applied (1 asb = 0.0929 fL = π cd/m²), convenient by that the product of required luminance (in asb) of the screen on its area (in sq. m) is the value of necessary light beam of a projector (in lm), which the more precisely, than reflecting ability of the screen is closer to 100%. Thus, the light beam of a projector for E-cinema should be numerically in 12·3.426·π ≈ 130 times more than the area of the screen expressed in m². As in process of the lump resource expenditure the light beam of a projector is lowered because of reduction of light efficiency of a lamp, this excess should be considered as minimal. As in cinema halls the wide-screen and general films may be shown, the universal screens of the widest format 1:2.35 with the motorized curtains covering redundant parts during display of films of other formats are applied. If the multimedia projectors of a format 3:4 will be applied to such screen, the essential part of their light beam will not be used. Really, the wide images occupy only a part of the projector gate, as shown in the figure. Therefore during display of a wide-screen motion-picture film by 1:2.35 format the redundant pixels of the projector modulators are switched off (they are painted over by blue and green). Hence, at an estimation of a necessary light beam of a multimedia projector it is necessary to accept the area of the screen in 2.35·0.75 ≈ 1.76 times more than actual area of the screen of 1:2.35 format.
The width of the screen image b (m) on the screen with high reflecting ability at determined luminance E (cd/m²) and at light beam Φ (lm) is estimated by expression b (m) = (Φ / πλE)1/2, where λ is formatted parameter, for example, λ1 = 3:4 of multimedia or λ2 = 9:16 of wide-aspect-ratio projectors. The convenient formula b ≈ 0.1(Φ)1/2 allows to estimate the screen width at its luminance Eλ1 ≈ 42.4 cd/m² and Eλ2 ≈ 56.6 cd/m². From here is follows, that with other equal conditions the wide-aspect-ratio projectors are provided on one third ligher luminance of the screen image, i.e. their application into E-cinema is advantageous. As the real light beam even at a new videoprojector is normally 25% less than promoted, a passport light beam of a projector should be not less than in 100 times to exceed a square of screen width. Perceptibility of the screen image pixelizationThe preferable distance from spectators up to the screen and a corner of its viewing during oversight of digital images is depended from the screen size and the system resolution. The studies have shown that spectators prefer to sit closer to the screen and to see it under angle exceeding 30°. The feeling of a reality (effect of participation) is increased with raising of the angle up to 100° and continues to grow until there is perceptible the pixel structure of the picture as the grid imposed on it. It is accepted, that resolution of vision makes one angular minute (under such corner we see stars in the sky). Hence, as imperceptibility margin of the pixel grid on the screen such distance from the screen up to the first row of spectators at which on one degree of vision of the screen 60 pixels are fallen may be accepted. At the same time, pixels of the LCD-projectors modulating transmission light, are represented the small squares, divided by opaque partitions, which size is approximately in 2.5…3 times less than transparent (active) part of pixel. Let’s assume that the screen image by the format 1:1.78, created by a projector with such modulators, contains 1080 horizontal lines with 1920 pixels in each line. Then the margin of the grid imperceptibility will be such arrangement of the first row from which on every pixel of picture in vertical direction it is fallen not more than 1 + (2.5…3) = 3.5…4 angular minutes of vision. Thus the field of vision of the whole image makes (3.5…4) · 1080 / 60 = 63…72° in vertical direction and (3.5…4) · 1920 / 60 = 112…128° in horizontal direction, that corresponds to the ratio of the screen height to distance up to the first row of spectators within the limits of 0.8…0.7. The projectors with modulation of reflected light beam are provided by the less distance between pixels, that provides the imperceptibility of pixel grid at application of such projectors with smaller resolution. For imperceptibility of pixel structure of the wide-screen image in a cinema hall with the lay-out shown in the third table if to take the criterion “not more than four angular minutes on a pixel”, the picture should contain not less 68 · 60 / 4 = 1020 pixels in each line in horizontal direction. The projectors with resolution not less 1024 · (1024 · 9/16) = 1024×576 (wXGA in terminology of computer graphics) are satisfied to these requirements. Thus, the resolution of projectors at E-cinema should be not lower than the wXGA level. Technology of projectionBy biological compatibility the closest are the images projected by liquid crystal projectors (LCD, D-ILA, LCOS, SXRD) as they are projected not line-by-line, but as a sequence of ready slides, that is almost the same as in a film cinematography. All pixels of these slides are simultaneously updated with it frame or multiple frequency, and without blanking of the screen and obturator overlapping of the frame gate needing in television and classical cinematography for invisibility of reverse motion of scanning and smearing of the image at film frame changes accordingly. The images formed by micro mirror projectors (DLP) the specific psychological load as visual averaging of luminance and color tones of all details of each frame are made. For a long time it is noticed, that the color palette of the images created by one-matrix (Single Chip) DLP-projectors, is perceived differently and their viewing results in fast fatigue because of necessity of visual averaging of luminance and especially of chrominance of each pixel. In a word, the proved opinion already exists, that DLP-images are not quite compatible with human nature, and single chip DLP-projectors though are ideal for mobile presentation, should not be applied for cinema show. “… The effect of ‘a rainbow’, consisting that the person sees the various color flashes instead of monophonic color, is only one of demonstrations of serial formation of chrominance. Many people are suffered from headaches and there are other unpleasant sensations. It is not yet known, that occurs with the person who nothing feels. It is possible, that as a result of passion by viewing of films on DLP-projector the person can be suffered from the cataract development or other illness…” M. Gabdrahmanov “Shine and poverty of DLP-technology”, Lay-out of cinema hallsAs at an initial stage of the cinematography development the projectors with the big light beam were absent, but everybody wanted to see the cinema, the normal, from the point of view of capacity, rectangular hall which length in 5 times exceeds a screen width was considered. In process of development of cinematography the good cinemas in the plan were began more and more “square”, and their capacity was increased both due to expansion of cinema hall, as due to the addition of balcony circle with seats. For designing of new cinemas and reconstruction of the big halls the lay-out versions adequate to specially requirements are applied. Characteristics of one of them with auditorium with 250 seats are given in the table.
In this case the width and height of the universal screen are 10 and 10:2.35 = 4.26 multiplicity accordingly, and angles of its vision in vertical direction from first and last raws of spectators are 32° and 14° accordingly. Thus from the first raw central seats the angles of vision of the wide-screen and general image in horizontal direction will be approximately 68° and 42°. Wide-aspect-ratio video projectorsUnder sufficient luminance and resolution the E-cinema projector must provide the projection with the maximal filling of the screen with aspect ratio 1:2.35. Overwhelming majority of multimedia projectors are equipped by light modulators of 3:4 formats, by lenses with an order of scaling up to 1.3, and their basic assignment is display of computer graphics. Powerful projectors of this series may be completed with replaceable optics, but as it was already marked, they are inefficient by way of the light beam application. Moreover, under projection of the wide-screen image 1:2.35 the resolution of wide-screen projectors in vertical direction decreases by 24% and under projection of general image (3:4) — by 43% in comparison with nominal value.
In figure the conditional 1:2.35 screen is framed ((its edges are painted by magenta) and is shown, in what manner the images from projectors with wide-aspect-ratio gate (9:16) under exact width filling of such screen are felt on. As the images by less wide formats are went beyond screen margin in vertical direction, they need to be scaled with demagnification from 2.35:1.85 (1.27) up to 1.34 for the images which are completely occupied the projector gate by it height. As a result the images of 1:1.78 (green frame) and 1:1.33 (blue frame) formats should appear inside black frame.
Hence, the E-cinema projector should be completed by replaceable optics providing the required projection ratios, or by a zoom with sufficient scaling value. Certainly, the second choice is more convenient in operation as does not demand the change of optics under demonstration of motion-picture films with different picture formats, but not all projectors may be provided by zooms suitable for concrete halls. From the last table follows, that at E-cinema with the specific area of 1 m²/seat the projector should provide not less than 25 lm of the light flux on each spectator.
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