Evening star. [volume] (Washington, D.C.) 1854-1972, 1894-01-13
LONG DISTANCE PHOTOGRAPHY.
Picture of Mont Blanc Recently
Taken From n Spot Eight Miles Away.

n PICTURE OF mont hl0nc Recently
Taken From n Spot Eight Miles Away.
A truly marvellous development in camera
work Is what has been termed telephotog.
raphy, whereby pictures of distant objects
can be made with the same clearness and
sharpness of detail as IL they were close at
hand. But to secure a successful picture by
this process many difficulties have usually
to be contended with, and according to the
Globe-Democrat 1t is compa "a lively seldom
that the most favorable conditions occur.
The main difficulty is the presence In the air
of minute particles of dust In large towns,
and even in their neighborhood, the air is
filled with an inconceivable quantity of such
particles. and the result is a grayness of
the atmosphere. which. on the Photographic
negative, blurs the outline OF remote OBJ
jects. Where these conditions obtain ii is
possible to procure a good proof only in the
morning. after a nocturnal shower has
cleared the air. Such Is the absorbent power
of dusty air that all attempts at taking
long distance photographs in the vicinity of
Paris, where much experiment ting was done.
resulted unsatisfactory beyond a range of
300 yards, even when the occasion was
apparently propitious. In the neighborhood
of the sea and of the mountains. where the
air is much purer, photographs can be made
at much greater distances; but here a singu-
lar obstacle presents itself in the unequal
density of the various strata Of air. Es-
pecially in hot weather certain beds of air,
heated by the rays of the sun, will be actu-
ated by an upward movement and this i'm
parts a trembling appearance to the land
scape. The presence of rivers. or marshes,
or land much exposed to the solar rays, is
likely to give rise to vertical currents of
vapor of great absorptive power. Again,
the humid vapors of the atmosphere clothe
far distance with blush haze, which con-
fuses the lines of the picture and obscures
the effects of light and shade. This is RENE
died by employing orthochromatic lenses and
yellow glass to neutralize the blue tint.
The camera must be absolutely still, the
most minute vibration being multiplied in
definitely and causing hopeless confusion in
the negative.
1t Will thus be seen that telephotography
Is both difficult and a delicate process. A
most remarkable illustration of it's posi-
bilities has been achieved by M. Boissonnas
of Geneva, in a photograph Of Mont Blanc.
taken at a distance of eight and one-half
miles. The proof has been published by NJ
Fourier, who also shows, in order to sug-
gest more strongly the wonderful nature
of the achievement, the size the picture
would be If taken by an ordinary object
glass. The latter measures GIG inches by
3-S inches, and the telephotograph is 3-4
inches by "a inches. The lines of the mas
sive, far-oh mountain stand out in bold re-
lief. and the details of the intervening
country are distinctly shown. Such a pic
ture, however, is not made without almost
unlimited pains and perseverance. 1t cost
NJ. Boissonnas four months of experiment
ing before he could determine on the best
place and the best time at which to take it.
For the benefit of those who may have to
tread YEARLY over the same ground, he tells
the conditions that obtained at the eventfui
moment. 1t was q o'clock in the evening,
about twenty minutes before the sun sank
behind the mountains. From experience he
found that this was the most favorable mo-
ment to obtain a harmonious proof. and the
distinctness of outline and details in the
clouds was greatly increased from the fact
that they were tinged first with pale yell
low and then with orange.