comptée dans le plan des clichés, et A une constante qui constitue le seul para 
mètre de la formule qui doit être déterminé par l’expérience. 
Si l’appareil stéréoscopique comporte des prismes ou des miroirs, les distances 
cl et s concernent le plan image des clichés par rapport à ces systèmes. Si l’appa 
reil comporte un système de lentilles tel que le grossissement angulaire résultant 
est G, il faut, en première approximation, remplacer la distance d par d : G. 
Si la formule (2) se révélait, à l’usage, insuffisante pour couvrir tout le domaine 
de l’observation stéréoscopique artificielle, il suffirait de prendre un plus grand 
nombre de termes dans la série, et de déterminer les coefficients par l’expérience. 
La détermination de ces coefficients est susceptible d’apporter en retour une aide 
aux recherches physiologiques, et de préciser la correspondance entre l’espace 
objectif et l’espace visuel. 
D’autre part, le facteur E étant ainsi déterminé, on peut se proposer d’étudier 
son influence sur les 'pentes apparentes du modèle. Ce calcul est rendu plus 
simple, sans rien perdre en généralité, par les relations de correspondance affine 
précisées par l’auteur. 
P. L. Baetslé: Vertical exaggeration in the observation of stereograms. 
In spite of the fact that numerous articles in the physiological publications are devoted to 
binocular vision, the author has not been able to find any that should be immediately applicable 
to vertical exaggeration in photogrammetry. The paper of C. 0. Roelofs and W. P. C. Zeeman 1 
about apparent size of objects can nevertheless suggest a way to a provisional solution. 
Since experience shows that the exaggeration factor must be univocally defined only by the 
geometrical circumstances of observation, a functional relation may be admitted to exist between 
the geometrical convergence and the »physiological» one. The exaggeration factor can then be 
expressed by formula (1), wherein the function y of c has to be determined by considerations such 
as the conclusions of the paper quoted above. Among the many possible expressions for y when 
expanded in series, one may choose a very simple one, that leads to formula (2); in this formula, 
only one parameter is to be determined experimentally. 
Some quantities appearing in the formula are to be interpreted in such a way that the optical 
systems of the stereoscopic device can be taken into account. 
If practical use shows that formula (2) does not cover all cases of artificial stereoscopy, the 
series proposed for y should be extended to a greater number of terms, involving more parameters. 
Such determinations are in turn able to strengthen physiological knowledge, and to bring clearness 
into the relationship between objective and visual spaces. 
On the other hand, once the exaggeration factor has been determined, one must calculate its 
influence upon apparent slopes. This calculation is made easier, without losing generality, by a 
simple law of affine correspondence, stated by the author. 
P. 0. Fagerholm: Stereo vision capacity of 900 tested persons of different age 
and profession. 
In order to get an approximate base-material for developing a method and 
an instrument for testing of stereo-vision capacity, the author has tested (1949— 
1954) 900 persons. 
The tests have been made with: 
1. A lens-stereoscope with the old Zeiss’ test picture »Prüfungstafel», with 
circles and other geometric signs, which has been modified. 
2. With polaroid Wirt Stereotest. 
Rather great differences have been established between the results with the 
two methods. Preliminary values for both methods for the variation of the 
stereovision capacity with sex, age, eyebase etc. have been determined. It seems 
to be quite obvious that the lens stereoscope test, when testing persons unac 
customed to stereoscopes, binoculars etc., can give misleading results. 
P. 0. Fagerholm: Priifung des Stereosehens. 
Um ein approximatives Grundmaterial fiir die Entwicklung einer Priifungsmethode zu schaffen, 
hat der Verfasser (1949—1954) das Stereosehenvermogen fiir 900 Personen untersucht. 
Zwei Methoden sind gebraucht worden. 
1 Ophthalmologica, 129 (1955,1) 166—86. 
P. 0. Fagerholm: 
Stereovision capacity of 
900 tested persons. 
149