REPORT.OF COMMISSION VII 63
azines increased, the more the blue part of the radiation disappears, then the green,
, and and, at last, the red. Thus, the rays travel with less interruption the longer the
sport- wave length used.
nlarg- Finally, the ability of penetration of the long-wave radiation depends on the
ke up nature and size of the particles met. If these are of very small size, as in haze,
small the long-wave rays are only slightly bent. When the size of the water particles
n the approaches that of those in damp fog, the deflection is considerable. Fogs are
usually more or less impenetrable obstacles even for the long-wave radiation.
posed Undesirable rays are absorbed with the help of suitable color filters. At very
>xam- great distances, and in hazy weather, it is advantageous to use infrared-sensitive
Insti- negative material, and a filter which permits the passage of the infrared and also
nse of
about
| prin-
tates
nove-
n the
ut 0.5
same
t, the
in the
. The
( 34.3"
aking
/scope
rama. FrG. 2. Swedish built long distance reconnaissance camera, about 10 ft. in length.
ircuit. (Manufactured by AGA, Stockholm-Lidingo.)
LATE some of the visible red, but, on the other hand, absorbs all other radiation.
> the | À wood, which cannot be penetrated on account of blue haze, appears in the
at the | infrared photo as very detailed terrain with individual trees and bushes standing
posite | out. In like manner, the details of a ship are reproduced with absolute clarity
| cm.) |
ishore | FrG. 3. Swedish built long distance camera Ju.
with a focal length of 96" (250 cm.) and f/15,
ulated | mounted on a temporary stand for operation from
| long | the top of a slope in ‘terrain. The constructor of
Isider- the camera, Mr. E. Aulin, with his assistant, Mr.
esired R. Melander, is pointing out the telephone post,
one mile away on the other side of a valley, to
which they afterwards drove in order to be long
eously distance photographed, See Figs. 5-7. (Manufac-
n also tured by AGA, Stockholm-Lidingô.)
ter at |
World |
of the | in infrared photos, in spite of the diffusing effect of the distance haze. However,
satisfactory results are often achieved even with the now faster and faster pan-
color chromatic emulsions which are very sensitive to red, together with suitable
taking | red filters.
e sun- | As already mentioned very long focal lengths are usually used when taking
solid, long distance photographs. As a rule, one tries for very detailed pictures, but
-wave often must be content with a scale which permits nothing more than identifying
short- the target. A scale of 1:10,000 may be taken as a suitable minimum, and is
ince is | obtained with a camera with a focal length of 118" (300 cm.) at a distance of 18.6
