DOCSLIB.ORG

Thickness Uniformity of Kodak Aerial Films

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Thickness Uniformity of Kodak Aerial Films B. C. MICHENER~ Eastman Kodak Company Rochester, N. Y. 14650 Thickness Uniformity of Kodak Aerial Films The maximum thickness variation found in the film was less than two-thirds of that allowed for the platen of the camera. ERIAL PHOTOGRAPHIC films are manufac- negative-type films intended primarily for A tured in various thicknesses to meet the conventional reconnaissance and photogram- requirements of different systems which use metric applications. This support is about 20 aerial photography as a means of recording to 25 percent thinner than the cellulose ester- information. The thickness of an aerial film type film bases which were used for so many is mainly determined by the thickness of the years for these types of aerial films. The transparent plastic material used for the film physical characteristics of the 102 pm thick support. The film support in all Kodak aerial Estar base are vastly superior to the former films is polyethylene terephthalate, a poly- thicker cellulose ester film supports. ester resin, which Eastman Kodak Company Estar thin base and Estar ultra-thin base calls Estar* polyester support. At the present supports are for aerial films used in sophisti- time Estar support is made in four different cated reconnaissance systems where maxi- thicknesses for aerial film use. Included in the mum footage and minimum weight are a ABSTRACT:Eastman Kodak Company conducted an extensive series of tests on one of its popular aerial films which has Estar as its base-Kodak Double-X Aerographic film 2405. The materials were tested with a special electrome- chanical thickness gage which had an accuracy of 2.5 pm and a sensitivity of 0.25 pm. As the emulsion and film-backing coatings are very thin relative to the Jilm base, and also have relatively small thickness variations, any noticeable variation in total thickness was essentially due to that of the base itself. The maximum variation amounted to approximately 9 pm. Thinner film bases had still smaller variations. official name of each aerial film are adjectives prime requirement. Some conventional aerial which give the film support thickness as cameras can successfully use Estar thin-base shown in Table 1. products but film transport and flatness Estar thick base would produce a film too problems can exist in other cameras. The use thick and stiff to give good performance in of Estar ultra-thin base films requires spe- existing aerial cameras so presently this sup- cially designed systems for satisfactory port is not used for aerial negative-type films. performance. It makes an excellent support for aerial dupli- As the photogrammetrist is mainly con- cating film where dimensional stability is the cerned with films on 102 pm Estar base, the prime consideration. Films of this type are balance of this paper will deal primarily with beginning, in some applications, to replace the thickness and thickness variations of these glass diapositive plates used in stereo plotters. products. The three principal aerial camera Estar base, with a thickness aim of 102 pm, negative films used in mapping produced on is the film support mainly used for camera this base are listed in Table 2. There is a difference of 14 pm in the thick- ness aim among these three products. The t Presented at the Symposium on Image Defor- mation, Ottawa, Canada, June 1971. difference is entirely in the thickness of the * Estar is a registered trademark. light-sensitive emulsion. Color-film emulsions THICKNESS UNIFORMITY OF KODAK AERIAL FILMS are generally thicker than black-and-white film emulsions because they contain many more individual layers. To maintain uniform photographic and sensitometric character- Thickness Aims, Micrometers istics within a product, it is necessary to con- trol precisely the thickness of the emulsion Static Resistanl Sup Emul- Total layers. The emulsion layers, being relatively Backing port sion thin and controlled within +5 percent, con- -- - Kodak Plus-X Aerographic tribute very little to the thickness variation film 2402 (Estar base) <1 102 7.6 110 of the total film. Results of several large studies have consistently shown that the Kodak Double-X Aerographic film 2405 (Estar base) <1 102 10.8 114 thickness variation in a complete film is no greater than that which exists in the film Kodak Aerocolor negative film 2445 (Estar base) <l 102 21.3 124 support on which the emulsion is coated. The static resistant backing on these three film products is a thin, transparent coating connected in series opposition. At some neu- which reduces the possibility of static elec- tral position of the armature, a null signal tricity generation. The backing layer being output results. The direction and magnitude extremely thin also contributes very little to of armature displacement from this null are the film's total thickness variation. indicated by the phase and magnitude of the The precise control over the thickness of output voltage from LVDT. the emulsion layers and the backing layer The amplifying equipment supplies the leaves the film support as the only significant 2400 Hz excitation for the transducer and contributor to thickness variations in the converts the electrical thickness indication complete film. into a form suitable for driving the recorder Thickness variations for this study were of the measuring instrument. These two measured on an electromechanical thickness items of equipment were manufactured by the gauge designed and built at Kodak Park. Sanborn Company in Waltham, Massachu- This gauge continuously records the thickness setts, and are designated as their Model of a section along a center line of a 35 mm 151-5460 Single Channel Basic Assembly wide sample. The instrument is capable of equipped with 150-110 Carrier Preamplifier. recording the sample thickness to an absolute The 35 mm wide sample to be measured is accuracy of 2.5 pm and of reliably detecting driven through the instrument by rubber- thickness variations as small as 0.25 pm. tired transport wheels located directly under A photograph of the thickness gauge is the pressure wheels. The transport wheels are shown in Figure 1. Operation of the measur- designed to give a sample speed equal to the ing device depends on a transducer which record-chart speed so that record and sample converts minute displacements into electrical can be compared directly. The measuring signals. The particular transducer used is a spindle that includes in its structure the commercially available "Linear Variable Dif- armature of the linear variable differential ferential Transformer" (Schaevitz LVDT- transformer has a replaceable, hardened, Model 100ML). It consists of three coaxial spherical shaped, tool-steel point which rides coils wound on a ceramic tube and a soft iron directly on the film surface. The anvil over cylindrical armature which moves coaxially which the other surface of the film slides has within the coils. The center coil is energized a cylindrical surface of sapphire to minimize with a 2400 Hz supply. The outer coils are wear. The measuring spindle applies a force oi about 20 grams to the film surface. In actual use an accurate feeler gauge is used to preset the instrument so that the null point is located in the center of the trace. Thickness variations of f 12.5 pm can then Nominal Thickness be recorded using the full width of the re- Description of cording paper. Micrometers (pm) Inchas Shown in Figures 2 and 3 are typical thick- ness profile traces obtained on samples of Estar thick base 178 0.0070 Kodak Double-X Aerographic film 2405 Estar base 102 0.0040 Estar thin base 64 0.0025 (Estar base). The upper trace in each figure Estar ultra-thin base 38 0.0015 shows the thickness variation in the complete film while the lower trace was produced from ~HOTOGRAMMETRICENGINEERING, 1972 I - )' , I hi* FIG.1. Thickness recording gage. the identical strip after the emulsion layer variation in this profile is greater than the was chemically removed. These traces graphi- average found in a large study. cally show that variations in film thickness Thickness profiles of complete films are not are primarily the direct result of thickness made routinely so, as part of this study, a variations in the film support. Figure 2 shows full-width production roll of Kodak Double-X a profile having about a 1.3 pm thickness Aerographic film 2405 (Estar base) was ana- variation over the 24 crn distance and repre- lyzed for thickness variation. Several strips sents a flatter than average film. The profile 35 mm wide were cut across the width of the in Figure 3 shows about a 5 pm thickness master roll at two locations about 30 meters variation which occurs over a distance of apart. The remaining film between these about 6 cm. As will be shown, the thickness locations was then slit into 35 mm strips in Canplete film - Emulsion removed 24cm b FIG.2. Thickness profile of Kodal Double-X Aerographic film 2405 (Estar base). THICKNESS UNIFORMITY OF KODAK AERIAL FILMS --- Comlete film I Emulsion removed I FIG. 3. Thickness profile of Kodak Double-X Aerographic film 2405 (Estar base). the length direction of the roll. Thickness shall not depart from a true plane by more profiles were made of these strips. than 13 pm (0.0005 inch). The variation al- Included in the analysis of these data was lowed in the unevenness oi the camera platen the thickness variation found within a 23 cm is over 50 percent larger than the average X23 cm (9 inchesX9 inches) film format. The thickness variation found in the film. thickness variation was determined in 54 Standard deviations of the thickness varia- locations over each 23 cmX23 cm-format. tions were also calculated for across-the-width This procedure was repeated on 96 formats and along-the-length of the master roll.
Load more

Recommended publications
  • Photographic Films
    PHOTOGRAPHIC FILMS A camera has been called a “magic box.” Why? Because the box captures an image that can be made permanent. Photographic films capture the image formed by light reflecting from the surface being photographed. This instruction sheet describes the nature of photographic films, especially those used in the graphic communications industries. THE STRUCTURE OF FILM Protective Coating Emulsion Base Anti-Halation Backing Photographic films are composed of several layers. These layers include the base, the emulsion, the anti-halation backing and the protective coating. THE BASE The base, the thickest of the layers, supports the other layers. Originally, the base was made of glass. However, today the base can be made from any number of materials ranging from paper to aluminum. Photographers primarily use films with either a plastic (polyester) or paper base. Plastic-based films are commonly called “films” while paper-based films are called “photographic papers.” Polyester is a particularly suitable base for film because it is dimensionally stable. Dimensionally stable materials do not appreciably change size when the temperature or moisture- level of the film change. Films are subjected to heated liquids during processing (developing) and to heat during use in graphic processes. Therefore, dimensional stability is very important for graphic communications photographers because their final images must always match the given size. Conversely, paper is not dimen- sionally stable and is only appropriate as a film base when the “photographic print” is the final product (as contrasted to an intermediate step in a multi-step process). THE EMULSION The emulsion is the true “heart” of film.
    [Show full text]
  • Graphic Materials: Rules for Describing Original Items and Historical Collections
    GRAPHIC MATERIALS Rules for Describing Original Items and Historical Collections compiled by Elisabeth W. Betz Library of Congress, Washington, D.C., 1982 WordPerfect version 6/7/8 (July 2000; with MARC21 tagging added March 2002) With cumulated updates: 1982-1996 and List of areas to update for second edition: 1997-2000 Cover illustration: "Sculptor. Der Formschneider." Woodcut by Jost Amman in Hartmann Schopper's Panoplia, omnium illiberalium mechanicarum aut sedentariarum artium genera continens, printed at Frankfurt am Main by S. Feyerabent, 1568. Rosenwald Collection, Rare Book and Special Collections Division. (Neg. no. LC-USZ62-44613) TABLE OF CONTENTS Graphic Materials (1996-1997 Updates)...................p. i Issues to consider for second edition (1997-2000).......p. iii Preface.................................................p. 1 Introduction............................................p. 3 0. General Rules........................................p. 8 0A. Scope.............................................p. 8 0B. Sources of information............................p. 9 0C. Punctuation.......................................p. 10 0D. Levels of description.............................p. 12 0E. Language and script of the description............p. 13 0F. Inaccuracies......................................p. 14 0G. Accents and other diacritical marks (including capitalization)..................................p. 14 0H. Abbreviations, initials, etc......................p. 14 0J. Interpolations....................................p. 15 1.
    [Show full text]
  • April 29–May 1 Dryden Theatre
    DRYDEN THEATRE APRIL 29–MAY 1 2016 DEDICATION The 2nd Nitrate Picture Show Festival of Film Conservation Dryden Theatre April 29–May 1, 2016 2 decades. 226 students. 28 countries. Honorary President Kevin Brownlow Celebrating 20 years and a lasting Museum Director Bruce Barnes impact throughout the world. Festival Director Paolo Cherchi Usai Executive Director Jared Case Technical Director Deborah Stoiber “The only way to learn how to be an archivist is to get your hands dirty working in an archive. The Selznick School afforded me the opportunity Curator of Film Exhibitions Jurij Meden to dive into my work, to absorb the knowledge of my teachers and to Special Events Director Allen Buell learn how to do things for myself. It taught me how to troubleshoot in Registration Coordinator Caroline Yeager a field where problems are a dime a dozen. I’m not sure if I would be Hospitality Coordinator Daniela Currò ready, willing, or able to handle my position today had I not attended Student Coordinator Jeff Stoiber the Selznick School.” Nitrate Projection Manager Ben Tucker — Andrew Lampert, archivist, Anthology Film Archives Nitrate Projection Specialist Spencer Christiano Class of 2003 Designer Amy Schelemanow Catalogue Editor Ryan Conrath “The Selznick School is like a good wine: It’s getting better and better Copy Editor Molly Tarbell with time (and with no vinegar syndrome!). I belong to the first class Assistant Designer Amy Slentz of students who completed this program in a new millennium. Saving Public Relations Manager Kellie Fraver our moving image heritage for the future generations is a deeply Dryden Theatre Manager Malin Kan important task.
    [Show full text]
  • IPI Storage Guide for Acetate Film
    IPI Storage Guide for Acetate Film James M. Reilly • Director, Image Permanence Institute Instructions for Using the Wheel, Graphs, and Table Basic Strategy for Film Preservation l The IPI Storage Guide for Acetate Film provides an overview of environmental specifications for film storage. It explains the relationship between temperature, relative humidity (RH), and “vinegar syndrome,” the slow chemical decomposition of acetate plastics leading to loss of their value in a film collection. l The main purpose of the Guide is to help collection managers evaluate the quality of the storage environment they provide for their film. The Guide is not meant to predict the life of any individual film; it merely uses predicted life span as a yardstick to measure the quality of the storage environment. l CONTENTS What the Guide Is (and What It Is Not) ................... 2 The Wheel ................................................................ 4 Time Contours for Vinegar Syndrome .................... 7 The Time Out of Storage Table ............................... 8 Chemical Deterioration of Film Bases .................. 10 The Course of the Vinegar Syndrome .................. 13 Does the Guide Apply to Nitrate Film? ................. 15 Polyester Base Film ............................................... 15 The General Philosophy of Film Storage .............. 16 History of Film Supports ........................................ 21 References ............................................................. 23 ANSI and ISO Film Storage Standards ................. 24 Rochester Institute of Technology, 70 Lomb Memorial Drive, Rochester, NY 14623-5604 Phone: 716-475-5199 Fax: 716-475-7230 Image Permanence Institute Image Permanence l WHAT THE GUIDE IS (AND WHAT IT IS NOT) The IPI Storage Guide for Acetate Film is a tool for evaluating and planning storage environments for acetate base photographic film, cinema film, and microfilms.
    [Show full text]
  • Preservation of PHOTOGRAPHIC MATERIAL Preservation of Photographic Material
    Preservation of PHOTOGRAPHIC MATERIAL Preservation of photographic material Introduction Photographs are housed in libraries, archives and museums all over the world. Practical photographic conservation treatment provides an option for photographs that are damaged or have deteriorated. However, it is also possible to prolong the life of a photograph through good preservation practices in handling, housekeeping and storage. This booklet describes the most common historical photographic processes, outlines the causes of deterioration and provides guidelines on good preservation practice. It is aimed at people working or volunteering in libraries, archives and museums whose responsibilities include working with photographic collections. Whilst the booklet focuses on historic black and white or monochrome photographs, much of the information is applicable to colour photographs and other imaging materials such as microfilm, x-rays and motion picture film. What is a photograph? A photograph is an image produced by the action of light. The light initiates a chemical reaction which leads to a long-lasting chemical change in a light-sensitive compound bound to a support. The support is usually made of paper, plastic, glass, or metal, but is sometimes made from other materials such as leather or cloth. Photographic images are usually continuous in tone, meaning changes in shading between light and dark are gradual and no patterns are seen, such as the regularly spaced dots or grids found in photomechanical printing processes. History Photography was officially invented in 1839 with the public announcement of Louis Jacques Mandé Daguerre’s daguerreotype process in France and William Henry Fox Talbot’s photogenic drawing process in England.
    [Show full text]
  • The Essential Reference Guide for Filmmakers
    THE ESSENTIAL REFERENCE GUIDE FOR FILMMAKERS IDEAS AND TECHNOLOGY IDEAS AND TECHNOLOGY AN INTRODUCTION TO THE ESSENTIAL REFERENCE GUIDE FOR FILMMAKERS Good films—those that e1ectively communicate the desired message—are the result of an almost magical blend of ideas and technological ingredients. And with an understanding of the tools and techniques available to the filmmaker, you can truly realize your vision. The “idea” ingredient is well documented, for beginner and professional alike. Books covering virtually all aspects of the aesthetics and mechanics of filmmaking abound—how to choose an appropriate film style, the importance of sound, how to write an e1ective film script, the basic elements of visual continuity, etc. Although equally important, becoming fluent with the technological aspects of filmmaking can be intimidating. With that in mind, we have produced this book, The Essential Reference Guide for Filmmakers. In it you will find technical information—about light meters, cameras, light, film selection, postproduction, and workflows—in an easy-to-read- and-apply format. Ours is a business that’s more than 100 years old, and from the beginning, Kodak has recognized that cinema is a form of artistic expression. Today’s cinematographers have at their disposal a variety of tools to assist them in manipulating and fine-tuning their images. And with all the changes taking place in film, digital, and hybrid technologies, you are involved with the entertainment industry at one of its most dynamic times. As you enter the exciting world of cinematography, remember that Kodak is an absolute treasure trove of information, and we are here to assist you in your journey.
    [Show full text]
  • The Acetate Negative Survey
    THE ACETATE NEGATIVE SURVEY FINAL REPORT A PROJECT FUNDED BY THE UNIVERSITY OF LOUISVILLE AND THE NATIONAL MUSEUM ACT David G. Horvath University of Louisville Ekstrom Library Photographic Archives February 1987 The University of Louisville Photographic Archives Ekstrom Library Louisville, KY 40292 ACKNOWLEDGMENTS The subject of this study should be of great interest to those who are responsible for the preservation of historical photographic negatives. It has involved the cooperation and advice of many people who, piece by piece, have helped construct the method, process, and format of the final product. My wife, Mary has been very supportive and kept me from becoming discouraged by the endless details of the project. My colleagues at the Photographic Archives were most helpful in their constant encouragement, suggestions and warm friendship, especially Andy Anderson, Bill Carner, and Barbara Crawford; Michel C. Atlas was invaluable for her editorial contributions. I thank the National Museum Act of the Smithsonian Institution and the University of Louisville for their assistance and support, especially Barbara Schneider and Martha Bowman, the University of Louisville Librarian. I am indebted to all the institutions which allowed me access to their collections and provided me with a wealth of background information upon which much of this study is based. I owe special thanks to Ford Peatross, Carol Johnson, and Stephen Ostrow of the Library of Congress; Amy Doherty of the Special Collection Department at Syracuse University; Tim Peterson
    [Show full text]
  • The Dangers of Cellulose Nitrate Film INDG469
    Health and Safety Executive The dangers of cellulose nitrate film This leaflet is aimed at private individuals and voluntary groups who have or find old film in domestic or other non-workplace premises. It gives advice on: ■ why cellulose nitrate film is hazardous; ■ how to identify cellulose nitrate films and negatives; ■ how to recognise signs of decomposition; ■ what to do if you have cellulose nitrate film; ■ contact points for information and advice. The leaflet does not cover requirements for the storage and handling of a large number of cellulose nitrate films and negatives such as may be found in archives on commercial or industrial premises or in museums. Exacting standards are defined for such activity (see British Standard BS ISO 10356:1996 and National Fire Protection Association Code NFPA 40), and it is covered by workplace health, safety and fire legislation including the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). Cellulose nitrate film is extremely dangerous. It catches fire very easily and once alight is difficult to put out. Fires involving cellulose nitrate burn extremely quickly with a hot, intense flame and the smoke is particularly toxic, containing large quantities of poisonous gases. Any cellulose nitrate film that you come across now will be extremely old. This is a problem because the high fire risk from cellulose nitrate film increases as it ages. Old cinematographic film and old photographic negatives (including X-ray film) may be made from cellulose nitrate (which means they contain nitrated cellulose or other nitrated product). These films are sometimes referred to as ‘nitrate’, ‘nitrate-based’, ‘nitro-cellulose-based’ or ‘celluloid’ film (although the term ‘celluloid’ is often used these days to refer to film in general, the film may not actually contain cellulose nitrate – see identification methods later in the leaflet).
    [Show full text]
  • KODAK PARK Its Products and People on the Cover: Testing a Kodak Color Film
    KODAK PARK Its Products and People On the cover: Testing a Kodak color film. Copyright 1951, 1953, and 1954, Eostman Kod.ok Company, Rochester, New York Photography in Action POWERFUL, dramatic, this news picture sym­ bolizes one important field-the press­ through which photography enters your daily lives. Other photos on the next two pages also show how photography furthers human knowl­ edge, enjoyment and progress. PLANT TOURS. .. th . V, s,tors rn rOUgh Frida ay take 9U;d ys, except hol"d ed tours of K d layS, beginn; 0 ok Park on M ng at 9:30 a ondoyS ·rn . and 1.30 . P.rn . Shooting an industrial scene on 16mm motion-picture film. 4 PICTURES: - In Worlc and Play COME with us via this brief booklet on a tour of our Kodak Park Works. For we'd like to show you how some of the "raw ma­ terials of photography" are produced in this, our largest plant. From Kodak Park to customers in many lands go shipments of Kodak films, papers, plates and chemicals. They are some of the "sensitized" materials that help to make modern photography. For these materials "react" when ex­ posed to light. And that is the basis of photography-the action of light on a chemical! y prepared substance. For aerial photography. The pictures you see on these two pages show a few of the ways-and the results­ ~~- of using some of the products we make here. But they only begin to tel! the part pho­ tography plays in your life today.
    [Show full text]
  • PRESERVATION of MOTION PICTURE FILM a Background
    .. I ?I! YlCTdRE, GROADCASTlM ' :,XCORDED SUUND DIVISION PRESERVATION OF MOTION PICTURE FILM A Background Paper for the National Film Preservation Board Milton R. Shefter MILJOY ENTERPRISES, INC. Preservation Consultation and Project Management January, 1993 MlWOY ENTERPRISES, INC. - PRESERVATION OF MOTION PICTURE FILM Motion picture film is now 100 years old. Since Edison and Eastman collaborated through their companies to produce continuous rolls of film at a standardized width of 35mm, our visual cultural history has been recorded in theatrical, documentary and newsreel forms. The light and shadows, which later included color, have enthralled, entertained, educated and emotionally moved audiences since the beginning of the century. Tragically, half of the 21,000 films produced in the first 50 years no longer exist. They are lost, destroyed or deteriorated. Time, the greatest enemy of motion picture film, claims more victims each day. The necessity for preservation of motion picture film is a given. The need for immediate action is what we must address now. Motion picture film was never designed to be long-lasting. Early films were produced for weekly runs at "nickelodeons" and then had no further use. While prints of some of these early productions still survive, most of the original elements that produced the screening prints have deteriorated into oblivion. To understand the need for film preservation, one must examine the physical properties of film as well as its subject matter. Film, physically, is comprised of three main layers: emulsion, adhering binder and support base. The emulsion is a colloidal (gelatin) medium which contains dispersions of light-sensitive materials.
    [Show full text]
  • 5.2 Types of Photographs, Part 1: 19Th and Early 20Th Century
    PRESERVATION LEAFLET PHOTOGRAPHS 5.2 Types of Photographs, part 1: 19th and Early 20th Century Gary Albright Conservator in Private Practice Monique Fischer Senior Photograph Conservator Northeast Document Conservation Center INTRODUCTION Coated paper: A support that has a binder layer on its surface consisting of albumen, gelatin, or collodion. This layer holds the This leaflet introduces the different types of photographs and light-sensitive photographic salts. A three-layer structure has as their distinguishing characteristics and should serve as a basic its third layer barium sulfate (aka Baryta layer). This layer occurs guide in identifying individual photoprints and negatives. between the paper and the image layer. DEFINITIONS Uncoated paper: A paper support without any binder layer. The First, a few useful terms and concepts: image often appears to be within the paper. POP (printing-out paper): A photographic paper that forms a DISTINGUISHING CHARACTERISTICS visible image directly from the reaction of light on light-sensitive When considering a photographic object, there are a few materials. POP prints are warm in tone, tending towards a primary features to consider: brown, purple, or reddish color. They are usually made in contact with a negative. 1. Positive or negative 2. Nature of support material DOP (developing-out paper): A photographic paper that forms a 3. Texture, surface quality visible image using a chemical developer to reveal the latent 4. Color, tone image made by exposure to light. DOP prints are cool in color -- 5. Characteristics of deterioration blue, neutral, or black -- unless they have been toned or are faded/chemically damaged. They may be either contact-printed or enlarged from a negative.
    [Show full text]
  • Film Structure Film Structure
    FILM STRUCTURE FILM STRUCTURE What is motion picture film? The American National Standards Institute (ANSI) describes it as “a thick flexible strip of plastic, complying with a dimensional standard as defined within, whose use is specific to the process of manufacturing a motion picture.” That definition leads to about a dozen pages of further definitions about various aspects of motion picture film. For our purposes, let’s take a look at how film is made, and how an image is formed on that film. THE STRUCTURE OF FILM Film is made up of layers, and it’s the combination of these layers that give each film its character. Motion picture film consists of a transparent support film base, a light-sensitive emulsion, and a number of layers coated on both sides. Some layers are diEerent from those coated on still film and are designed to help motion picture film travel smoothly through the camera. Film Base The supporting layer in film is called the base. This base has to be transparent (with some optical density), free from imperfections, chemically stable, insensitive photographically, and resistant to moisture and processing chemicals, while remaining mechanically strong, resistant to tearing, flexible, and dimensionally stable. Three plastics have been widely used as a motion picture film base: • Cellulose nitrate was the first material used. Discontinued in the 1950s because it was highly flammable, cellulose nitrate is chemically unstable if stored in conditions that are too damp (it can decompose) or too hot (it can self-ignite). • Cellulose acetates were developed to replace nitrate. Cellulose triacetate, called safety base, is much safer to use and store than nitrate.
    [Show full text]