( TRAINING to be able to execute a visual task is closely related with 
Learning. We probably say "training" when the learning process is 
carried out more consiously than in the case of learning of primary 
visual acts, and often think of repetition, of practicing a task, up 
to the stage where performance satisfies ourselves or our instructor. 
It surely has in common with learning the "do-it-yourself" routine = 
— but training is more associated with drill and drive, whereas 
learning to see simply is an internal must, 
Training counteracts visual fatigue, up to a certain degree, as 
everybody knows. It also improves pointing accuracy, to mention just 
one particular visual act which is important for photogrammetry, but 
9 it is largely unknown how effective it is and what period of training 
  
is necessary and optimum. Recent research on parallax clearance 
capability of a skilled operator astonishingly gave at each weekly 
. . 47 . n " . nico 
repetition a 10% improvement, even after 6 weeks (Hempenius, 1968). 
  
lobviously, training, by often carrying out a task, is rather 
essential to maintain a good performance or a high efficiency. 
For photo-interpretation, Vernon's conolusions are valuable 
(Vernon, 1962, p. 241): "It is natural to suppose that people do 
vary in their capacity to perceive, or at least to cognize 
their surroundings, just as they vary in their other psychological 
  
  
capacities. This variation may be merely one of efficiency; some 
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people perceive more quickly and accurately than do others. 
Undoubtedly some people are better able than others to control 
the direction and concentration of their attention. These varia- 
tions are to a considerable extent functions of training and 
experience, but they may also have an innate basis, like intellec- 
  
tual efficiency. ..... . Some investigations suggest, that people 
tend to be relatively more efficient in some types of perception 
j and in some perceptual situations than in others." 
Ali-round perceptual efficiency cannot be obtained by training, 
probably the information handling capacity is limited by design] 
[LL ADAPTATION covers in this context &ll aspects of learning and momen- 
tary changes of the visual sense, which serve the purpose of being 
prepared for the perceptual task. lt is possible to distinguish 
between gradual adaptation, instantaneous adaptation, conscious and 
unconscious adaptation, and so on. Geometry lessons on school and 
perspective drawing exercises probably will train hand and eye 
muscles both, such that straight lines can easily be distinguished 
from slightly curved lines, and perpendicular line crossings from 
oblique intersection of lines.