Film-Tech Forum ARCHIVE: Kinoton reverse scan sound scanner

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Posted by Patrick de Groot (Member # 858) on 11-14-2004, 11:18 AM:

I did a test to see if the distance between picture-sound was good. I found that with the analog laser sound pickup the diamond was centered in front of the laser and the correspondending countdown number was in front of the gate. However with Kinotons newer digital/analog reverse scan sound device the diamond ended up in front of the digital sound LED/reader (the first LED the film comes accross)! A design fault?

Posted by Michael Schaffer (Member # 1204) on 11-14-2004, 02:36 PM:

The distance between aperture and analog reader is defined by the size of the lower loop and (obviously) threading the projector correctly. This can also be used to make up for the time it takes the sound to travel in very large auditoriums. For instance, if you have a very long room, you can make the lower loop a little smaller.

Posted by John Pytlak (Member # 331) on 11-15-2004, 09:02 AM:

Standard SMPTE 40 specifies the distance between the 35mm picture and corresponding analog sound to be 21 frames. Threading with 21 frames between picture and sound should produce "dead sync" at the screen speakers, and would be appropriate for a drive-in or small screening room. Since sound takes about 1/24 second (one frame) to travel to the central seating area of a mid-sized auditorium (approximately 50 feet from the screen speakers), most thread with 20 frames between picture and sound.

Posted by Patrick de Groot (Member # 858) on 11-15-2004, 03:06 PM:

I did know all what you said already (by finding the info here on the forum). Thats why I tried it out to see it myself (Kinoton FP 30).

However, as I said before, with the analog laser reader the theory stands, but with the newer digital/analog red led the diamond ends up in front of the digital led (first led the film passes when running). This can't be corrected by making the lower loop smaller... I think it isn't a problem, but it doesn't comply with the standard.

Anyone else tried this with a Kinoton reader?

Posted by Stephen Furley (Member # 1277) on 11-15-2004, 03:38 PM:

I haven't seen the new Kinoton sound head, all the machines II've run have had the old one. Do you mean that the sound head is closer to the gate than you expected, or further? By how much?

If the soundhead was lower than the standard, then the sound would be out of sync; I cannot believe that Kinoton would design it that way, and that nobody would have noticed it by now if they did.

The soundhead can be mounted higher than standard if the reproduced sound is delayed to bring it back into sync with the picture. I do not know if the Kinoton analogue head has such a delay. I can think of a case where this is done, the Kinoton 16/35 machines have the 16mm sound head above the gate, but 16mm optical sound is printed 26 frames in advance of the picture. The required delay, from pictures of the machine it looks like about 2-3 seconds, is provided dgitally.

Of course, digital tracks are also read ahead, in the case of Dolby penthouse readers, very much so.