FILM PRODUCTS FOR AERIAL PHOTOGRAPHY 
J. J. Graham - 
Manager, Aerial Products 
Eastman Kodak Company 
ROCHESTER N.Y. 14650 
U.S.A. 
Both the need and value of aerial photography have been well established for many years. 
Applications of the technique abound and new applications are being put to use regularly. Today more 
and more city planners, land managers, cartographers, geologists, oceanographers, foresters, engineers 
and scientists are depending on aerial photography to assist them in their daily activities. 
Development in aerial films produced by Kodak have been keeping pace with these new applications. 
Improvements have been made in film sensitivity, granularity, resolving power and sharpness. In 
addition, all Kodak aerial films, because of their polyester base with thinner harder emulsions, can be 
processed in modern continuous high speed processors. Coupled with the emulsion technology that pro- 
vided harder thinner emulsions with lower swell and therefore reduced carry out are new easy to mix 
chemical processing solutions that permit lower replenishment rates for each film. 
FILM BASE 
A new class of polymers called polyesters which could be formed into plastic sheeting and film base 
was developed after World War II and was used with aerial films in the early 1960's.  Polyethylene 
terephthalate is one of these polyesters and can be made from ethylene glycol and dimethyl tereph- 
thalate by ester interchange and polymerization with the elimination of methanol. This poly-conden- 
sation reaction requires a suitable catalyst and heat. 
Since polyethylene terephthalate is insoluable in common solvents, it is impractical to use the 
solvent-casting method. Therefore, this material is converted to film base by the melt-casting process. 
The methods developed for the melt-casting and biaxial orientation of polyesters, such as polyethylene 
terephthalate, are given in literature ("Properties of Kodak Materials for Aerial Photographic Systems 
Kodak Aerial Films and Photographic Plates," M-61, page 27). The molten polymer is fed into an 
extrusion hopper and forced through a long, narrow slot onto the casting wheel where the molton 
material is rapidly cooled. This is followed by the orientation process in which the sheet is 
stretched in both width and length at a carefully controlled temperature. The original cast sheet, 
therefore, must be several times the thickness desired in the finished film base. Stretching the sheet 
under proper conditions causes the long polymer molecules to become oriented in the plane of the film 
with resulting improvement in flexibility, strength, and other physical properties. 
The stretched polyethlene terephthalate film base is next "heat set" by heating it while it is 
under tension to a temperature above that used for orientation. Crystallization occurs, and the 
density of the sheet increases. This treatment locks the polymer molecules into place so that sub- 
sequent shrinkage of the sheet, at temperatures up to the heat-setting temperature is practically 
eliminated. 
At the present time, all Kodak aerial films feature ESTAR Base. This polyester forms an out- .. 
standing base for these products because of its toughness, flexibility, and stability. Although it is 
made as uniaxial as possible in production, a slight predominance in molecular orientation may prevail, 
and the direction of this orientation may not coincide with either the length or the width of the film 
strand. 
ESTAR Base is manufactured in four standard thicknesses: 
ESTAR Ultra-Thin Base mils ( 38 ym) 
1.5 
ESTAR Thin Base 2.5 mils ( 64 um) 
ESTAR Base : 4.0 mils (102 um) 
7.0 
ESTAR Thick Base mils (178 um) 
Of these, the 7.0-mil product provides the best dimensional stability, and the 1.5-mil base gives 
the greatest square footage of film in a given volume. 
EMULSION TECHNOLOGY 
Emulsion technology continues to progress providing us with finer grain, higher resolution and 
faster speed films. A comparison between KODAK PANATOMIC-X AERECON Film Type 3410, now discontinued, 
KODAK High Definition Film Type 3414, and KODAK PANATOMIC-X AERECON II Film Type 3412 illustrates such 
improvements. 
A good example of these advances is the requirement for a film that would extend flight times 
because of sun angle, minimize IMC compensation and increase shutter speed but have low-grain and high 
resolving power. 
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