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The Set: Pete Deksnis's Site about the CT-100

Restoring a Vintage Color Television Set


Subject: color CRT soapbox
Date: Thu, 02 May 2002 03:28:44 -0500

Hi Pete,

As you well know, original NTSC had real good, wide gamut colorimetry, even better than the present standards for ATSC HDTV. But, over the years, the set makers compromised the wide gamut in the “brighter is better” wars of the late '50s to the 1970s.

By 1974, the images were much brighter, but red had become orange and green had become yellowish green to squeeze more light out of the CRT designs. The SMPTE (Society of Motion Picture and Television Engineers) revised the old NTSC standards and developed an RP (recommended practice) for monitor standards to try for consistency, even if the gamut was less than ideal. Their RP became what is now known as the SMPTE-C color coordinates recommended for color video broadcast monitors.

This was a way smaller gamut than your old 15GP22, but at least it was a defined standard. Up until then, the colorimetry of monitors was all over the place, and it was impossible to predict what anything would look like anyplace. Once this RP was in place, at least among studio monitors there was a consistency of color display, so product shots could look consistent from one monitor to the next.

The big fight in recent decades has been to get the TV set manufacturers to understand how important these standards are. Not until the home theater industry evolved with videophiles concerned about image quality did something start to happen on the home TV set field. As a result, you can actually buy a home set these days with something close to SMPTE-C colorimetry, but not too close to the original NTSC wide gamut specification -- unless you get a projection set equipped with color trim filters built into the projection lenses of the red and green CRT's (or you bought one of those Princeton color corrected HD monitors).

Toshiba was recently building these filtered CRT's for Princeton for a while when Princeton was building a special high-resolution multisync 32-in. 16:9 aspect monitor used for HD displays. These things were relatively cheap for a while but are no longer being built. Too bad, as the pictures looked great on them with the wide gamut display. Not exactly true 1953 NTSC, but closer than just about anything else in a direct view set built in the last 40 years. And, it was bright enough not to be viewed only in a dimly lit room. Much brighter than a 15GP22.

There is a lot of discussion being put into a study of colorimetry for setting standards for Digital Cinema. These guys (researchers, scientists, and engineers in the digital cinema electronic display fields) have a chance to get it right this time. I'm an observer of the discussions via emailed transcriptions of a committee of the SMPTE (Society of Motion Picture and Television Engineers) dealing with these issues. It's a hotly debated topic, and I'm hoping they come up with some good standards that will give the public the kind of wide gamut and accurate colorimetry we have all deserved, but have not gotten for all these years from either film or television.

Looks as though we may have a winner eventually, but the issues are hotly contested. The hardware used for large-screen projection is fully capable of being designed to give wide gamut color and bright images using current knowledge and light valve technologies (DLP, LCOS, ILA, etc.) if carefully built to tight standards.

I better step off this soap box before I fall off and get hurt.

Dave Corbitt, Telecine CRT Support: Sales and Engineering