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Posted by Paul Konen (Member # 41) on 08-19-2002, 11:38 AM:
 
What is the "Official" spec for frame offset of visual image to analog soundtrack?

The information would be great just by itself with a link being even better.

Thanks
Paul.
 


Posted by Josh Jones (Member # 447) on 08-19-2002, 11:46 AM:
 

I believe the SMPTE specifies a 21 frame offset from the analog sound scanning area to the picture aperature.

Josh
 


Posted by John Pytlak (Member # 331) on 08-19-2002, 03:20 PM:
 
Standard SMPTE 40 specifies 21 frames +/- 1/2 frame in the direction of travel during normal projection.
http://www.smpte.org/smpte_store/standards/

Thread with a 21 frame offset if you are very close to the speakers (e.g., a drive-in or small screening room). Otherwise, subtract a frame, assuming 50 feet from the screen speakers (sound takes about 1/24 second to travel 50 feet).

Bob Throop made a good catch, which I corrected:
"John,
You mean subtract a frame Don't you?"

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion


 


Posted by Robert Throop (Member # 61) on 08-19-2002, 03:55 PM:
 
John,
You mean subtract a frame Don't you?

------------------
Bob Throop
 


Posted by Kenneth Wuepper (Member # 1174) on 08-19-2002, 04:07 PM:
 
Lip Sync

Some academy leaders have strange diamonds between the count-down numbers. These have a purpose!

When a numbered frame in in the PROJECTION aperture (not the threading window), the diamond should be at the light slit in the standard mono reader.

I received a call from the manager the first night we were opening "The Godfather one". The laboratory was on the phone and I had to go down to the office to receive specific directions.

The lab had spliced a "watermelon girl color test" in the middle of the opening credits. The screen is black and the titles appear in the center of the screen as white letters. We had to get the color test out of there before the first showing.

The second direction was the one stated above regarding the lip synch threading. Marlon Brando whispers during much of the dialogue and so the lip synch was critical. Yes, we adjusted the loop for the size of the theatre. (2,125 seats)

Just thought you might like to check out your threading. I put a label in each sound head with the required number of frames in the after intermittent loop.

KEN
 


Posted by Brad Miller (Member # 2) on 08-19-2002, 05:46 PM:
 
With the Christies you have at your theater Paul, you really don't have a choice if you don't want to have film damage. Make the lower loop no larger than by this setpoint:

With film threaded, open the lower pad roller assembly and turn the projector over by hand. Make the lower loop small enough such that it tugs on the pad roller. One perforation at a time increase the size of the lower loop until it no longer tugs on the pad roller as the projector is being advanced manually (by hand). Once you reach that setting...GO NO LARGER!!! Personally I prefer the loop be as large as I can get it with it still tugging on the pad roller.
 


Posted by Paul Konen (Member # 41) on 08-19-2002, 06:28 PM:
 
Brad, that is how I get them to thread today. My point that I am wanting to enforce with my staff is that there is an offset between image and sound track.

The main problem is with the Coke ads. I need to train them where to cut the head so as not to destroy any audio. (It can be done). The staff I have seem to interested in projection so I can do some double education. This will also incorporate cue placements which also have an impact on presentation. Placed too close to the end of the black leader, audio / visual information lost. Placed too far away, uncomfortable silence until information is projected.

These small things can make a difference.

Paul.
 


Posted by Gordon McLeod (Member # 33) on 08-19-2002, 08:33 PM:
 
Thread the word picture start in the gate and then place the sound sync diamond across the reader
No other method works
 
Posted by Kenneth Wuepper (Member # 1174) on 08-19-2002, 10:08 PM:
 
Rule for Sync

I purchased a stainless steel frame ruler from Victor Duncan which has this critical spacing plainly marked. The ruler lives on the edge of the rewind table. This is also helpful in determining frame lines for the black lead ins of trailers.

KEN
 


Posted by Paul G. Thompson (Member # 655) on 08-19-2002, 11:02 PM:
 
Are we saying 21 frames inclusive? Or just 21 frames?

If you have 16 frames per foot, and the sound diamond is four frames away from the 16th frame, the last time I added 16 + 4, it came out to 20.


 


Posted by Steve Guttag (Member # 268) on 08-19-2002, 11:47 PM:
 
The 1 frame in advance is there (20 frames) since no one is sitting at the screen...a 1/24th second advance is built into the leader or 41.67msec....using kitchen physics...that is about 40 feet for sound. So the sound should appear dead-sync about 40 feet from the screen. Not too unreasonable. In larger theatres, you will want to shorten the loop some but it is a balance for the bulk of the crowd.

Steve

------------------
"Old projectionists never die, they just changeover!"
 


Posted by Paul G. Thompson (Member # 655) on 08-20-2002, 01:25 AM:
 
The more I think of it, the more I get screwed up. This picture is what I am trying to say:

Actually, I should have put a "0" in front of the 1 on the top count. That would show 21 frames inclusive. I should have flipped the picture horizontally so it makes more sense.

But anyway, you guys are providing some darn good information. Now if I can just get it to sink in... 21 frames (inclusive) ahead of the picture. (mumble mumble mumble)

John and Steve...is the 21 frame count shown on the bottom of my picture is what you are referencing? Then it makes sense. When I went through the MPO school in San Diego, they tested on "20 frames"...but apparently they were not counting the frame that is being projected. After 35 years of wrestling with this issue, I think I understand now...Thanks!

Thanks for the tip, Brad. I'll pass that one along to the others who run the Christies, too.

Paul Konen, This might help your operators, too.
http://www.wrslabs.com/filmsound.html

The last paragraph of that page says:

Sound Overlaps

In 35mm prints, sound overlaps are required at the roll changeover in theatrical projection. (Ref: ANSI PH 22.55). Whenever composite prints are made in multiple reels, where these reels might be splices together for projection, a sound overlap is required of the print at the end of the reel being spliced onto the head of the next reel. This overlap contains the sound information of the advance of the next reel (26 frames in 16mm and 20 frames in 35mm).

ARG!!!! Back to the 20 frames thing again. No wonder some people get confused!


 


Posted by John Pytlak (Member # 331) on 08-20-2002, 07:12 AM:
 
Standard SMPTE 301 "Theatre Projection Leader, Trailer and Cue Marks" specifies a distance of 20 frames between the "Picture Start" (frame 27) and the "35mm Sound Start" diamond (frame 7), and repeated every 16 frames though the length of the leader. Threading with 20 frames between the picture aperture and the analog sound slit will put the sound in sync about 40-50 feet from the screen.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
 


Posted by Christopher Seo (Member # 7) on 08-20-2002, 11:27 AM:
 
Paul,

I too thought I understood this, and then got confused again, until I read the actual SMPTE wording which is crystal clear: the optical track "shall be displaced longitudinally from the center of the corresponding picture by a distance of 21 frames +/- 1/2 frame in the direction of film travel"... (emphasis added)

So each 1/24 sec. soundbite is printed alongside the 21st frame before the corresponding picture frame, give or take.


 


Posted by Frank Angel (Member # 248) on 08-20-2002, 12:11 PM:
 
Some of the old Academy leaders (some are even in use today) make it easy. There is a PICTURE START frame and a SOUND START frame. Put the PICTURE START frame in the aperture, thread so your loops put the SOUND START frame at the slit and you've got it.

But then comes the fly in the ointment -- you look at the soundtrack and you see the start marks, those XXXs on many prints, and you see that they don't line up with the XXX's in the picture frame; logic tells me that these are supposed to be exactly together for correct sync. Yet I see lots of prints where these lineup marks don't match each other, sometimes by one or two sprockets, some as much as a full frame....even two. We are pulling hairs here over +/- half a frame to get perfect sync, when the pic neg/sound neg line-marks up can be off by more than that. And of course over the years all of us have gotten prints that had reels that were definitely out of sync -- OK if they were out in the direction that a shorter loop would correct, but you're up the creek if it is out in the other direction.

This has happened often enough to make me wonder why projector manufactures never designed a "sync" adjustment much like the framing adjustment, where just turning a knob would either shorten the distance between the aperture and sound scanner or lengthen it. Seems like that would be an easy addition to any projector or sound head design. You could then thread fix sync printing anomalies on the fly.

This would allow you to just "dial in" the distance in feet from the screen where you want lip-sync to be perfect. If you have a big house like I do, the projectonist could even adjust that point to match where the bulk of the audience is sitting for each show!


Frank

 


Posted by Jeffry L. Johnson (Member # 453) on 08-21-2002, 07:31 AM:
 
The Bauer U 2 has a "loop former" on the take-up sprocket that allows you to change the size of the lower loop while the projector runs.
 
Posted by Frank Angel (Member # 248) on 08-21-2002, 12:21 PM:
 
You mean they stole my idea?
 




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