[rollei_list] Re: Rollie R3 film
----- Original Message ----- From: "Carlos Manuel Freaza" <cmfreaza@xxxxxxxxxxxx> 
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, July 30, 2007 2:31 PM
Subject: [rollei_list] Re: Rollie R3 film



Richard, the film base support for the R3 is
polyester, not cellulose and it is one of the most
advanced films made today.
Multiple layer emulsions are not new. They have been used for decades to extend the density range of the film and tailor the characteristic curve. Multiple layers are also used in some color films. Agfa, for instance had two or three layers for each color. I think this was partly to control the curve shape but may also have been to allow different couplers in each coating. If R-3 is based on Agfa technology it likely has more than three layers. Agfa also included separator layers. They may not be needed in a B&W silver film. Some of their films had something like 12 or 14 layers. All of these must be extraordinarly thin, the coating technology is quite awe inspiring. Most color films have the anti-halation layer under the emulsion. It is indeed a better way to do it than including a dye in the back coating and also eliminates problems with light-piping. Light piping is why 35mm B&W negative films have a pigment in the support, the under the emulsion anti-halation layer eliminates the need for this. However, there is probably still a back coating to reduce curling. Curling is due to the difference in expansion/contraction of the emulsion and support. The use of a polyester support, such as Kodak Estar, results in excellent dimentional stability plus the material is supposed to be much more resistant to change with time than any of the cellulose bases. However, it still requires subbing to make the emulsion stick to it. Somehow the roll under discussion got subjected to something that made the entire emulsion and back coating come off. The emulsion will come off in one piece even though it is made up of several coatings. 

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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