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equipment and a Fairchild dryer with solution temperatures usually between 
65 and 70°F to produce gammas with an average value of 1-2. A wedge is 
processed with each film to check processing. Mechanically driven spool tank 
developing equipment with A5 type dryers are used by another firm with solu 
tion temperatures of 60 to 65°F in the United Kingdom and 60 to 75°F outside 
the United Kingdom. This equipment produces gammas of 1 • 2 to 1 • 6. Routine 
sensitometric control is used only in the one case indicated. Storage conditions 
for film handled by this last processing equipment are as follows: The film is 
kept in the sealed tin provided by the makers until 24 hours before exposure 
and is then conditioned to 70% relative humidity and 65°F. The film is recon 
ditioned between processing and printing to 70% relative humidity and is stored 
at 70% relative humidity and 65°F. 
Finland 
For most work Kodak Super XX topographic base film is used. It is pro 
cessed by winding it back and forth between two reels and is air dried on reels 
3 metres in diameter. Solution temperature is 17-5 to 18-5°C. A gamma of 
about 0-8 is obtained. There is no routine sensitometric control. 
For forestry purposes some Kodak infrared aerographic film is used. 
France 
Regular IGN surveys are photographed on Panchroquil fast panchromatic 
plates manufactured in France by the Société Guilleminot, Boespflug et Cie. 
Their speed is approximately 100 ASA and their resolving power on high con 
trast target is 14 microns for a complete period. The veiling density is ()• 18 and 
the gamma used is 1-2. The support material is drawn glass of thickness 1-7 
mm +0-1 mm. The tolerance on flatness is 0-01 mm. The back of the plate 
is coated with non-sensitized gelatin so that flatness will not be affected by 
humidity changes. A semi-automatic developing machine to handle 2,000 to 
3,000 plates per day is in an experimental stage Refrigeration and electrical 
heating will control the bath temperatures at 18°C. 
Plates for tropical use are coated with a gelatin tanned at a high fusion 
point. They are wrapped by dozens in paraffin paper and shipped in zinc-lined 
cases which contain the quantity required for two magazines. 
The film used is French Kodak Pathé Super XX with an ASA speed of about 
100, resolving power of 15 microns, a veiling density of 0-15 and a gamma of 
0-9 which is considered somewhat low. The support is cellulose triacetate. IGN 
tests of dimensional stability have shown that aceto-buterate gives the least 
mean shrinkage followed by triacetate, diacetate and nitrate. However, the 
advantage of the aceto-buterate over the triacetate with regard to isotropy of 
distortion is not very pronounced. Film rolls are supplied in taped tins. After 
processing the films are stored flat at 18°C ±1° and 60 to 65% relative humidity. 
Films are processed either on the American Fairchild-Smith or the similar French 
Sauret equipment. 
Samples of negative materials used at IGN are checked by obtaining 
characteristic curves, spectral sensitivity, and resolving power under various 
conditions of development.