Running the soundtrack edge downward, toward the platter's surface puts the film at many potential risks, including severe horizontal "platter scratches" and emulsion side scratches should the film drag around the brain.  Running soundtrack down can also cause focus problems and erratic payout of the film.

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Preo and Yavitz documented a significant improvement in screen image quality when 35mm theatrical release prints were wound, used and stored consistently in an emulsion-in orientation, including minimal focus drift and a much lower tendency toward flutter and in-and-out of focus. BUT, their work was based on the performance characteristics (e.g., curl, core-set) of TRIACETATE base film, using small-hub (2000-foot) reels. Unfortunately, a similar study has not been done for today's POLYESTER print films which have different curl and core-set characteristics, or with platter performance.

That said, many on Film-Tech have noted that POLYESTER prints usually perform better when wound emulsion-out (analog soundtrack up) on a platter. With platters, the effect of winding orientation on focus flutter is much less important. Compared to a core or reel, the hub diameter is much greater, so there is little "core-set". The preferred winding orientation on a platter depends mostly upon the curl of the film, which in turn, depends upon the relative humidity in the projection room. Use the orientation that gives the best winding quality, and the least tendency for "static cling" in your situation. It may vary with the humidity.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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Does the film sometimes drag around the brain partway? If it is soundtrack up there is no need to let this worry you, for there isn't enough pressure against the base side to matter. However, if you are running soundtrack down having the emulsion drag around the brain will start making light scratches that are visible after a certain number of runs.

All polyester film comes with a negative curl. Lay a short strip of film emulsion down against the surface of a flat table. Note only the edges touch the table. Now lay the film emulsion up, away from the surface. Note that the edges of the film no longer touch the table, but the center of the film does. This sort of curl will be magnified if the film is stored emulsion in (soundtrack down) and will cause focus issues in some projectors. Winding the film emulsion out will help the film to "flatten out" as it stays wound that way.

SMPTE is out of touch.

I just wanted to know if there was more to this. I do know that many theatres do have emulsion-out, but were never really given a great description of WHY. Thanks for all your information.

I noticed that others have brought up Steve G. Would that be Guttag? If so, I was also interested to hear what he would say, besides that my projector is running.

Soundtrack-Up, so it will be. But I have always been annoyed with these polyester static problems. I have tried many items from humidifiers to just plain "babysitting". Guttag introduced me to FILM-GUARD (well, the company) and we have not really had the usual brain wraps as before. It could also be that we recently moved from our old location to a newly built theatre.

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Still, I think any good projectionist should take a good, hard look at his setup and decide which way is best. Who knows, you may have some difference in your system that demands the film be run a certain way. No matter what your decision you have to get everybody on the same page as far as threading and running goes. Everybody MUST thread the film exactly the same way. Loop-for-loop... Twist-for-twist... carbon copies!

I have been to so many places where the people all thread different ways and that has caused me no end of grief! It is nigh-on impossible to fix things when a film problem (like a wrap) occurs because you have to decode some kid's threading pattern before you try to fix it. Furthermore, when somebody calls me and asks about some problem (the film getting scratched, for instance) I have to spend 1/2 hour questioning people about the way they thread before I can even begin to help them. The first thing I usually end up asking is, "Who's in the booth tonight."

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"All polyester film comes with a negative curl. Lay a short strip of film emulsion down against the surface of a flat table. Note only the edges touch the table. Now lay the film emulsion up, away from the surface. Note that the edges of the film no longer touch the table, but the center of the film does."

Not always the case. Curl depends mostly upon the relative humidity tha film is equilibrated to. Film emulsion is mostly gelatin, which expands as it absorbs moisture, and contract as it dries out. Polyester film base is very stable as the humidity changes, so when the humidity changes, the film's curl will change as the emulsion shrinks or expands relative to the base.

Processed print film is designed to lie flat between 50 and 60 percent relative humidity. As the humidity gets below 50 percent RH, the emulsion shrinks more than the base, causing the film to curl inward toward the emulsion. This is termed "POSITIVE" curl, not negative as Brad described. In really damp conditions, the gelatin emulsion may absorb enough moisture to expand and cause the film to curl toward the base side -- this is termed "NEGATIVE" curl:
Definition of Curl
Description of Curl

Under very dry or very moist conditions, there may be enough positive or negative curl to cause winding difficulties (e.g., spoking, roll taking the form of a polygon rather than a circle). Use the winding orientation that give the best winding quality and least tendency to pull in with "static cling":
Platter Patter article

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

The SMPTE reviews and revises standards and recommended practices on a five-year schedule. It's likely the last review of RP39 was done before there was sufficient experience with polyester prints to make a change. It still does apply to triacetate prints.

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