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has been slowly ripening. The Photostereograph Beta was born in my mind with à 
pose — never admitted — of replying indirectly to criticisms made of me over in 
pathy I showed for the too simple direct optical projection plotters, but that m 
ment should, as they say, take me by the hand and go beyond my most LN 
hopes, proving to be an extremely simple instrument in spite of the category and M 
which it belongs, cannot but be a source of satisfaction for me and for photos 
who now have available a new plotter, whose principle and design confer MAN 
useful characteristics upon it. m 
Thus the Photostereograph model Beta/2 is a universal autographie plotter of t. 
order precision based on the Porro-Koppe principle, but one in which the Servitudes i. 
ing from the application of this principle in instrument designs as known today ki. 
eliminated, restoring to these plotters all the advantages that have always iem iy 
nized, without the burden of the complex and onerous mechanical and optical devices 
weighed heavily on their design and had a negative influence on the economy of ii 
practical use. t 
The cameras in the Photostereograph Beta/2 remain immobile when plotting; iy 
can be replaced with others with different geometric features with extreme od 
without disturbing the general adjustment of the instrument. 
Furthermore the plotter, independently of the cameras, permits the use of any fy 
of diapositives having different principal distances within limits more than sufficient f 
the normal differences that exist among the principal distances of the take cameras! 
the same model and the same geometric optical features. 
The mechanical optical system for bringing the images under stereoscopic obser 
is relieved of the need for an excessive accuracy of construction and for the req 
maintenance of a rigorous adjustment when plotting, because the images of the markal 
the photograph, in the form of parallel beams, fuse into one single image coming fm 
infinity, before entering the optical system, thus eliminating beforehand any worry ab 
the introduction of any dangerous parallaxes between the images of the photograph ai 
o 
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the mark. 
The Photostereograph Beta/2 possesses all those indispensable requisites for fi 
multiple uses that these instruments properly have; it permits, in fact, the comp 
rotation of the images of the cameras for both diapositive or negative use and peni: 
the transposition of the observation of the camera images with respect to the observatin 
eye-pieces for accomplishing the spatial triangulation; furthermore it is equipped vil 
an enlargement variator placed along the course of the optical train for the observatin 
of the photographs, thus compensating for the differences in scale which arise in i 
images, as dependent upon the angles of tilt of the beams emerging from the camer 
Its construction is extremely simple and strong, and the new arrangement of ft 
instrumental axes, which has permitted the shift of most of the weight below, assures f 
most complete stability of the plotter for the preservation of the optical model. 
The observation always takes place in the nucleal plane exactly as it takes phe: 
natural sight according to the gift with which Mother Nature has endowed us; it shout 
be remembered that the observation in the nucleal planes, which is an advantage oft 
Porro-Koppe principle, always permits stereoscopic viewing according to the maxim 
value of the linear parallax. 
The observation of the images of the stereos : 
photographs in their every point, as imposed by the principle on which some plotes 
based, does not provide any real benefit in comparison with the observation in the iii 
planes, as is shown by the fact that operators aceustomed to those types of plotter > 
with no difficulty in using plotters based on the Porro-Koppe principle. Thus i 
hypothesis which I have never found to be confirmed in practice even as it never 
been in the theoretical field. 
tits ois m i ati hat th 
Furthermore it is my personal opinion, one confirmed in practical use, that 
scopic pair normally at the plane qi 
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