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Hi All-
I looked for the NBC "Bonanza" memo this past weekend, and was unsuccessful, but I did locate two pieces of documentation related to this issue.
The first is a paper from the SMPTE "Color Television" collection dated November 1964, p.80, by Hank Kozanowski, head of advanced camera development at RCA, and the lead engineer on the TK-26. The paper is titled,"Infrared Transmission Characteristics of Various Color Release Prints and Their Effects on Color Television reproduction."
To receive the attention by Dr. Kozanowski, this subject had to have been of major importance. I have no doubt this was related to "Bonanza," as that show was likely NBC's biggest cash cow film program.
He describes tests done at NBC Burbank by Ken Erhardt on changes in telecine red channel black level adjustment when switching between Technicolor Imbibition print stock and Eastman 5385 film. Later, NBC-NY performed similar tests, affirming the Burbank results, showing a predominant red "haze" (elevated black level) from the Technicolor film.
Spectral measurements conducted in Camden revealed a 5-6 fold greater transmittance of near IR light in the 700-750 nM region of Technicolor print stock than the 35mm Eastman version. In addition, the original 1954 TK-26 red filter did not have a steep cutoff chaarteristic below 700 nM, but remained at about 20% transmittance beginning at approximately 650 nM.
Tests were conducted with a Technicolor T-1247 filter and also a filter from Fish-Schurman, both correcting the IR transmittance issue. The Technicolor filter began cutoff around 640 nM, and the F-S not as drastic. The final design was a combination red trim and IR cut filter, tested at NBC NY by Ed Betero, and installed in all NBC TK-26s, made by Fish-Schurman.
The second piece of documentation is an RCA Technical bulletin #G27 applying to all TK-26 models, encouraging customers to replace the original 1954 red filter with the better Fish-Schurman model, availabe from RCA as stock #230098. The change applied even to the TK-26C which was in production before the release of this paper.
The filter replacement addresses 4 items, according to the Tech Bulletin:
The modification was designed to improve the color fidelity and color balance tracking.
The amount of infrarared light transmitted through color film varies with the technique used in processing the film.
The red trim filter filter modification greatly reduces the amount of infrared light reaching the vidicon photo cathode.
The "red channel" pedestal shift, with changes in film of various processing techniques, is greatly produced. Thus the need to rebalance the equipment signals for changes in good color film is greatly reduced.
Again, I'm 99% certain this change was related to "Bonanza" and I'll keep searching for the NBC memo.
Regards,
JB
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