Editing NTSC (section)

==== SMPTE C ====
{{anchor|Color correction in studio monitors and home receivers}}

To ensure more uniform color reproduction, some manufacturers incorporated color correction circuits into sets, that converted the received signal—encoded for the colorimetric values listed above—adjusting for the actual phosphor characteristics used within the monitor. Since such color correction can not be performed accurately on the nonlinear [[Gamma correction|gamma corrected]] signals transmitted, the adjustment can only be approximated, introducing both hue and [[Luma (video)|luminance]] errors for highly saturated colors.

Similarly at the broadcaster stage, in 1968–69 the Conrac Corp., working with RCA, defined a set of controlled phosphors for use in broadcast color picture [[Display device|video monitors]].<ref name="DeMarsh, Leroy 1098">DeMarsh, Leroy (1993): TV Display Phosphors/Primaries&nbsp;— Some History. SMPTE Journal, December 1993: 1095–1098. {{doi|10.5594/J01650}}</ref> This specification survives today as the '''SMPTE C''' phosphor specification:<ref>{{cite web |title=SMPTE C Color Monitor Colorimetry RP 145-2004 |url=https://pub.smpte.org/latest/rp145/rp0145-2004_stable2010.pdf |access-date=July 15, 2024 |website=SMPTE}}</ref>

As with home receivers, it was further recommended<ref name="ITU470">International Telecommunication Union Recommendation ITU-R 470-6 (1970–1998): Conventional Television Systems, Annex 2.</ref> that studio monitors incorporate similar color correction circuits so that broadcasters would transmit pictures encoded for the original 1953 colorimetric values, in accordance with FCC standards.

In 1987, the [[Society of Motion Picture and Television Engineers]] (SMPTE) Committee on Television Technology, Working Group on Studio Monitor Colorimetry, adopted the SMPTE C (Conrac) phosphors for general use in Recommended Practice 145,<ref name="SMPTE_RP145">Society of Motion Picture and Television Engineers (1987–2004): Recommended Practice RP 145–2004. Color Monitor Colorimetry.</ref> prompting many manufacturers to modify their camera designs to directly encode for SMPTE C colorimetry without color correction,<ref name="SMPTE_EG27">Society of Motion Picture and Television Engineers (1994, 2004): Engineering Guideline EG 27-2004. Supplemental Information for SMPTE 170M and Background on the Development of NTSC Color Standards, pp. 9</ref> as approved in SMPTE standard 170M, "Composite Analog Video Signal&nbsp;– NTSC for Studio Applications" (1994). As a consequence, the [[ATSC standards|ATSC]] digital television standard states that for [[480i]] signals, SMPTE C colorimetry should be assumed unless colorimetric data is included in the transport stream.<ref>Advanced Television Systems Committee (2003): ATSC Direct-to-Home Satellite Broadcast Standard Doc. A/81, pp.18</ref>

Japanese NTSC never changed primaries and whitepoint to SMPTE C, continuing to use the 1953 NTSC primaries and whitepoint.<ref name="ITU470"/> Both the [[PAL]] and [[SECAM]] systems used the original 1953 NTSC colorimetry as well until 1970;<ref name="ITU470"/> unlike NTSC, however, the European Broadcasting Union (EBU) rejected color correction in receivers and studio monitors that year and instead explicitly called for all equipment to directly encode signals for the "EBU" colorimetric values.<ref name="EBU1975">European Broadcasting Union (1975) Tech. 3213-E.: E.B.U. Standard for Chromaticity Tolerances for Studio Monitors.</ref>