Film-Tech Forum ARCHIVE: Is P35-SL SMPTE signal level at Dolby level?

This is topic Is P35-SL SMPTE signal level at Dolby level? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005445

Posted by Warren Smyth (Member # 1838) on 10-12-2003, 11:42 PM:

I have been given some P35-SL signal level test film. I was actually wanting Dolby CAT 69 for Dolby level checks. I have been assured that P35-SL is at Dolby level and can be used as such, but I have always assumed that it is only 1,000 cycles reference only. Can any one confirm?

Posted by Steve Guttag (Member # 268) on 10-13-2003, 12:24 AM:

I do not believe you will find that it is at 50% modulation and as such, can NOT be used as a substitute for Dolby-Tone. P35-SL was intened to "balance" out the level between two-projectors for changeover back before Dolby. I think you will find that it is recorded substantially higher than 50% modulation.

I know that P16-SL (the 16mm equivalent) was recorded at 100% modulation.

Steve

Posted by Gordon McLeod (Member # 33) on 10-13-2003, 12:11 PM:

I don't believe there was a specified level for the SMPTE test film except it is high by a fair bit than 50% modulation of the dolby tone
The frequency doesn't really matter as DOlby tone is 800 and SMPTE is 1k
UltraStereo's 50% tone test film is 1KHz

Posted by Warren Smyth (Member # 1838) on 10-14-2003, 06:21 AM:

Thanks very much Gordon and Steve, you confirmed my view so I bought some cat 69T today. You are right, the P35-SL plays at a higher level. I would guess roughly about 6db. Once again, much appreciated.