1、 Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an internationally recognized standards-developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, includi
2、ng Standards, Recommended Practices and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and ITU.
3、SMPTE Engineering Documents are drafted in accordance with the rules given in Part XIII of its Administrative Practices. This document was prepared by Technology Committee A12. 1 Scope This standard specifies the spectral response of the photographic audio reproducer light source and receptor as a u
4、nit, including any optical filtering that can be interposed. The analog sound-track formats suitable for reproduction using such a reproducer include the cyan dye-only track (without redevelopment of silver) and both conventional and “high magenta” sound-tracks (with redevelopment of silver). 2 Norm
5、ative references The following standard contains provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this standard are encourag
6、ed to investigate the possibility of applying the most recent edition of the standard indicated below. ISO 20859:2005(E), Cinematography Spectral Response of Photographic Audio Reproducers for Analog Dye Sound Trcks on 35 mm Film 3 Spectral response 3.1 The peak or maximum response of the combined a
7、udio reproducer light source, filter and receptor shall be 660 nm + 20 nm 30 nm. 3.2 The integrated response of the unit to all wavelengths greater than 800 nm shall be less than 5 % of the total integrated response measured from 400 nm to 800 nm. Page 1 of 2 pages SMPTE 411M-2006 SMPTE STANDARD for
8、 Motion-Picture Film Cinematography Spectral Response of Photographic Audio Reproducers for Analog Dye Sound-Tracks on 35-mm Film Copyright 2006 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved June 27, 2006 SMPTE 411M-2006 Pag
9、e 2 of 2 pages Annex A (informative) Additional data The reproduction of analog photographic sound-tracks has long employed a tungsten light source and an infrared-sensitive photocell. The light beam is modulated by changes in the infrared energy absorption of the silver sound-track image. This prac
10、tice dates from black and white practice. When color release prints were introduced, the practice of redeveloping a silver sound-track, which consists of silver, magenta dye and cyan dye, was employed in order to maintain compatibility with all existing infrared-sensitive reproducers fitted to proje
11、ctors. A change to dye-only sound-tracks is taking place in order to provide environmental and other benefits. The elimination of the need for silver sound-track redevelopment allows a simplification of the color positive process with savings in the use of hazardous chemicals and water. Discontinuat
12、ion of silver redevelopment in release prints eliminates the discharge of silver into the environment because, when used, release prints are ultimately destroyed. The red-sensitive sound reproducers required for dye tracks employ solid-state light emitting diodes (LED) or lasers with a longer lifeti
13、me than tungsten lamps, providing increased reliability of sound reproduction in theatres. The conversion of sound reproducers from infrared-sensitive devices (for silver sound-tracks) to red-sensitive devices (for cyan dye sound-tracks) requires an intermediate sound-track format called “high magen
14、ta”. The “high magenta” sound-track eliminates the cyan dye from the silver sound-track, thus making the transmission level from 600 nm to 1 000 nm almost equal. This almost equal transmission range produces good sound quality, including cancellation of cross-modulation distortion, for infrared-sens
15、itive readers and all types of red-sensitive readers. A dye-only sound-track needs to use the dye density to modulate the scanning beam. Unlike the silver density that exists at all wavelengths, the cyan dye in film does not have sufficient density to modulate the scanning beam at wavelengths of les
16、s than 600 nm and at wavelengths of greater than 750 nm. Reading the cyan dye-only sound-track too far away from its wavelength of maximum absorption will cause degradation of sound quality (higher cross-modulation distortion, lower high-frequency response and lower signal-to-noise ratio). The purpose of limiting the spectral response of the audio reproducer is to use advantageously the absorption of the cyan dye image to modulate the scanning beam and to maintain the maximum sound quality of which the cyan dye record is capable.
