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This topic comprises 2 pages: 1 2
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Topic: 70mm filmwinds on platter
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Thomas Dieter
Expert Film Handler
Posts: 234
From: Yakima, WA
Registered: Jun 2004
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posted 03-18-2005 05:35 PM
Okay, now it's my turn to play newbie, granted I am one compaired to the amount of time I've been on FT. But, I can still teach alot of people that have had more experience in the booth than I, why certian things shouldn't be done. (see one of my post in AKA outing bad.... for more details)
Sence I've started work at the Picture Show at Altomonte Springs, I have heard more people refer to the sides of the film as Emulsion and Oxide. I don't under stand this, and it wasn't taught to me when I was in training. Naturally, I try to pick up on things, and figure out things on my own. I also hear "Emulsion Scratch" more often than I do anything else. How can you tell what side the scratch is on, with out touching the film? (Light Reflection?)
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 03-18-2005 07:25 PM
quote: Monte L. Fullmer
Any special reason for this [winding 70mm film emulsion in/base out], or is this the norm for 5/70mm winds.
All the relevant standard-setting bodies recommend that triacetate elements be would emulsion in for archival storage, as 'stretching' the emulsion exacerbates the effect of deformation caused by base shrinkage, and emulsion in helps protect the emulsion itself. The same does not necessarily hold true for projection in general, platter use and/or polyester prints, though; and in a projection context, this issue has been flogged to death in many previous threads.
One other reason why 70mm might always have been wound base out is that when you're running it reel to reel, you can't introduce a twist in the film path. So the oxide stripes have to be on the correct side of the film as it is pulled from the feed spool to make contact with the heads in the projector. Since you can only coat the oxide stripes onto the base side of the film, the orientation of the film as it is wound onto a projection spool does have to be standardised, because this affects the design of the film path components related to magnetic sound playback.
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 03-18-2005 08:00 PM
It's a bit difficult to describe without drawing a diagram! What I was trying to say is that the design of the mag head & scanning drum assembly in a projector needs the film to be entering the mechanism the right way round for the oxide to make physical contact with the head. Furthermore the oxide stripe can only be coated onto the base side. This is unlike with optical sound, with which a combined print can be struck so that either the base or emulsion side faces the projector's lens in order for the image to be the right way round. OK, almost all the combined optical prints you get nowadays are SMPTE, base facing the lens ones: but there are some DIN prints still kicking about. As far as the projectionist is concerned, though, getting the optical track the right way round is all (s)he needs to worry about. So in order to minimise the risk of a mislacing screw up, there's no need to standardise whether prints are supplied and shipped with the emulsion or base side facing outwards, because the layout of the film is not symmetrical.
The layout of a 70mm mag print does appear to be symmetrical at first glance. So in order to make sure that the SMPTE 'base facing the lens' orientation is followed through, you need to standardise which way round the mag heads are positioned in a projector's film path. It also helps a great deal to standardise which way round prints are wound onto reels, because at first glance the topography of the film looks symmetrical. As with a 35mm full-gate silent print you have to look a bit more closely to make sure that you're feeding it into the projector the right way round. So sticking to one orientation on reels when shipping 70mm mag prints around offers an extra safety net.
Point taken - the feed spool can be mounted so that the film is being pulled clockwise from 3 o'clock or anticlockwise from 9 o'clock to ensure the correct orientation as the film enters the projector, if necessary. I was just suggesting that the convention of winding 70mm prints one way reduces the chance of anything going wrong.
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Monte L Fullmer
Film God
Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004
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posted 03-19-2005 03:00 AM
What was Leo mentioning on winds, is like with me imaging that the platter deck is like a reel with one side of the flanges removed.
Imagine, with the decks turning in the anti-clockwise direction, the reel is "laying on it's side" turning in that anti-clockwise direction. Then, if we take this image and re-align ourselves by looking underneath at the deck's rotation and compare this rotating deck to a standard takeup reel's clockwise rotation on a projector. We would then see where the magnetic striping's position on the deck when it's winding back from the machine, being this deck is that takeup reel laying on its side, in the rotation of that required clockwise direction on the lower reel arm and spindle.
And this is why of my opening statement of "soundtrack down." (or base out..)
Same goes for 35mm "rewinds" and I can almost see why some theatres wind their prints soundtrack down - like an actual clockwise rotation of a takeup reel of a projector.
(if this makes any sense....one have to think reverse on this one).
.....
quote: Thomas Dieter
How can you tell what side the scratch is on, with out touching the film? (Light Reflection?)
easy way is to get the "reflection" of the film under light and one can see that the emulsion side has a sheen,semi gloss texture, whereas the base side has a more shiner side.
Big thing, even though this isn't always the case, with new prints that are heads up, mounted on the right spindle of the rewind bench, the lead is trailing off the left side of the reel, image is upside down, sountrack is towards you and the emulsion is on the outside.
Tails is the result when one notices that the image is right side up when tailing off of the reel, and emulsion is wound inboard (at most of the time..unless ones turns the film around on a Christie MUT during breakdown, which this is a small tip: on breakdowns on Christie MUTS, the soundtrack be facing inward towards the roller tower and away from you, since the reel is spinning in an anti-clockwise direction).
-Monte
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 03-19-2005 03:45 AM
Leo,
quote: Leo Enticknap
All the relevant standard-setting bodies recommend that triacetate elements be would emulsion in for archival storage, as 'stretching' the emulsion exacerbates the effect of deformation caused by base shrinkage, and emulsion in helps protect the emulsion itself.
The negatives which I had returned to me from a lab a few years ago were wound emulsion out; in response to a question from myself somebody replied that negatives are always stored this way. Cleary, original camera negs are intended for long-term archival storage; is there some reason why they are stored this way when the recommendation is for triacetate prints to be stored emulsion in? i.e. is there some difference between triacetate negatives and triacetate prints from the storage point of view?
quote: Leo Enticknap
One other reason why 70mm might always have been wound base out is that when you're running it reel to reel, you can't introduce a twist in the film path. So the oxide stripes have to be on the correct side of the film as it is pulled from the feed spool to make contact with the heads in the projector.
Yes, I agree with this.
quote: Leo Enticknap
Since you can only coat the oxide stripes onto the base side of the film, the orientation of the film as it is wound onto a projection spool does have to be standardised, because this affects the design of the film path components related to magnetic sound playback.
I don't follow this. The MOMI cinema used to run 70mm emulsion in on DP-70s when they had them; this is a link to Hugh's site: web page . The Empire Leicester Square can clearly be seen to be running the same model of projector, but feeding emulsion out. Both arrangements seem to work. If you had projectors designed so that the feed spool had to turn in one particular direction, then I would agree with you.
Strictly speaking, it is not correct that you can only coat the oxide on the base side of the film, though they will always be on this side with 70mm. With 8, 9.5 and 16mm the standard is to have the stripes on the side facing the lamp, not the lens, i.e. the opposite to the way it is on 35 and 70mm. This works fine if you want to stripe a reversal camera original, but causes problems if you need to stripe a contact print. A few years ago I had some 16mm film striped by EVT Magnetics, in Surrey. They were able to apply paste stripe to triacetate or polyester base, or to the emulsion side of film. (They could also apply laminate stripe to triacetate base.) The oxide emulsion used was different in each case; the emulsion side stripe was not quite as good as the normal base side stripe, but it an be done. There was also a device which removed the emulsion from the edge of 8mm film to allow laminate stripe to be applied to the emulsion side.
quote: Leo Enticknap
The layout of a 70mm mag print does appear to be symmetrical at first glance. So in order to make sure that the SMPTE 'base facing the lens' orientation is followed through, you need to standardise which way round the mag heads are positioned in a projector's film path. It also helps a great deal to standardise which way round prints are wound onto reels, because at first glance the topography of the film looks symmetrical. As with a 35mm full-gate silent print you have to look a bit more closely to make sure that you're feeding it into the projector the right way round. So sticking to one orientation on reels when shipping 70mm mag prints around offers an extra safety net.
I'm sorry, but I don't follow this either. I do find that particularly with polyester prints I sometimes need to look quite closly to see which is the emulsion side, but it would be difficult to mistake which side of a print the mag stripes are on, surely. If the leader is not striped then you only need to pull down to the start of the reel itself to check that you've got it right.
Something I've wondered about in the past: In the 'French' section of MOMI the picture was direct rear projected, i.e. no mirror. Was a special reversed print made for this, or was it a special projector, with the sound head on the opposite edge? Acording to a book that I've got the sound head on the GBN portable could be reversed to read from either edge of the film for this purpose.
Brad,
On this forum the terms 'track up' and 'track down' and often used to refer to the wind of a 35mm print on a platter, and these terms seem to be used to equate to 'emulsion out' and 'emulsion in', or have I got that the wrong way round?
If you were to pick up a print from a platter, and flip it over then the track position would have changed, but not the wind, emulsion in or out. Of course, the print would now be wound in the opposite direction, clockwise/anti-clockwise. If track up or down can identify which way a print is wound on a platter, does this mean that all makes and models of platter always rotate in the same direction?
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