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Question about transparency film


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#1 tanner wolfe

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Posted 09 May 2011 - 03:39 PM

I'm very curious what the substance is that the emulsion adheres to on a piece of film. Especially for transparency films like Velvia or Ektrachrome. This is not strictly a cinematography project that I'm working on, but I'm having trouble finding this answer anywhere else. I believe that the emulsion adheres to an acetate backing. Is there anywhere on the web that I can find a break down of the layers making up a strip of film. Pls. advise.

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#2 Charles MacDonald

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Posted 09 May 2011 - 06:55 PM

I'm very curious what the substance is that the emulsion adheres to on a piece of film. _This is not strictly a cinematography project _

HI Tanner, no it is certainly not a direct cinematography question, and it is one that requires a book rather then a brief answer..

Try looking at
http://www.fujifilm....4_datasheet.pdf If the current version is the one in my files, you want to look at section 16 or so,..
One note the layers are VERY thin, while the base is very thick, they don't show them to scale in that diagram.
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#3 John Salim

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Posted 10 May 2011 - 07:43 AM

Tanner,
Almost every 'camera' film ( stills and MP ) is coated on tri-acetate base, with the only example I can think of being Kodak EIR Infra Red film ( process EA-5 or E-6 ) which was coated on Estar ( polyester ) ....now discontinued.

There are polyester based films around, but these are generally 'scientific use' films, and of course some intermediate and most print films.

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#4 Nicholas Rapak

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Posted 10 May 2011 - 11:58 AM

As John said, almost all photographic films are coated on cellulose triacetate. One notable exception in the cine world is Fuji's Single-8 films. These are coated on a polyester base so 50 ft of film can fit in a cartridge.
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#5 Charles MacDonald

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Posted 10 May 2011 - 07:14 PM

As John said, almost all photographic films are coated on cellulose triacetate. One notable exception in the cine world is Fuji's Single-8 films. These are coated on a polyester base so 50 ft of film can fit in a cartridge.


Yes, the rule of acetate (triacetate) is true for film that goes in a camera. Prints used in teh theatre and elsewhere are always on Polyester these days. Almost every still camera film is also triacetate, although some of the Smaller makers like EFKE have switched to polyester as it is easier for them to obtain.
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#6 Alan Duckworth

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Posted 18 May 2011 - 06:51 PM

My understanding as to why camera stocks are still mostly acetate base, is that if there is a malfunction or jam the perfs will blow out of acetate and/or the film itself snaps, whereas polyester would not do so and therefore likely damage the camera.

You can easily test the film itself to see what the base is. Apply film cement or even just hardware store acetone to the film base - acetate will soften or dissolve, polyester will be unaffected. This is a destructive test, so use only an unimportant sample.
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#7 John Salim

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Posted 19 May 2011 - 04:04 AM

You can easily test the film itself to see what the base is. Apply film cement or even just hardware store acetone to the film base - acetate will soften or dissolve, polyester will be unaffected. This is a destructive test, so use only an unimportant sample.


....or you can try to tear the film.
Acetate will tear whereas polyester won't and will stretch before cutting your hand !

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#8 Tim Gray

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Posted 20 May 2011 - 09:44 AM

Sounds like you got your answers, but in the future, know that the Kodak and Fuji spec sheets for these films usually tell you what the film base is for still films. It varies depending on the format. For example, if you go to the following link, you'll see all the spec sheets for Kodak reversal still films. If you want to see the sheets for other films, click on the appropriate film category on the left, then click on the link 'Tech Pubs'.

The film bases and thicknesses for each format are usually listed on the first page of the pdf for Kodak films.

http://www.kodak.com...3319/1229/13395
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#9 Brian Pritchard

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Posted 21 May 2011 - 03:55 AM

....or you can try to tear the film.
Acetate will tear whereas polyester won't and will stretch before cutting your hand !

John S

A non-destructive test is to look at the film sandwiched between cross polariaers. Acetate will be opaque whilst polyester will be transparent.
Brian

Edited by Brian Pritchard, 21 May 2011 - 03:55 AM.

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#10 Brian Pritchard

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Posted 23 May 2011 - 10:24 AM

Here is a photo of a piece of acetate on the left and poly on the right seen through a pair of crossed polariser.

Brian
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