When we listen to someone speaking (or playing music), we are normally quite aware of being asked to enter into another dimension - beyond the physical world - a mental universe in which verbs prevail over nouns and where objects loose their stability and changes take over. On the other hand, when looking at images, this invitation into another world is much less overt. Perhaps because they too are objects, images draw us into the world they portray without explicitly declaring their intention. In fact it is quite difficult not to yield to this unpercievable illusion (it has taken philosophers and artists to denounce it), for images, thanks to a partial isomorphism with the space of our everyday experience, literally make us see their object. Even though they refer to something that is not there, images in fact represent the object as if it were right before our eyes (or try to take us where the object is). Perhaps, we allow them to delude us because the world they draw us into is much simpler than the one of actions and reactions we dangerously interact with in our everyday life. Hence, if we do not want to indulge in passive connivance with this illusion, we have to understand and constantly remind ourselves that images too are effects produced by human activity, even though with a different degree of independence from their object compared to music or voice sounds. This obviously applies to scientific images as well, no matter how impersonal and objective they claim to be.
By taking images metaphorically away from the light they too, just
like other objects, are normally bathed in, and by looking at them
in a backlight, we are able to realize that they are objects but
not the objects they pretend to be: they bear a mark of their production.
Something like a watermark, that can only be seen if it is held
up to the light.
Image classification
The main problem in classifying things consists in determining
which aspects are to be considered the most relevant and which are,
on the other hand, to be disregarded. The classification of scientific
images we are using here avoids considering the images in themselves
(photo/graphics, color/black&white, still/movie, etc.) or in terms
of their scientific content only (biology, physics, geology, etc.),
dealing instead with the relationship between the image and its
object. Rather than a classification of images, you could say it
is a classification of the scientific usage of imaging techniques.
The main divisions are firstly between the techniques that produce
images as direct recordings of a real object and those that use
scientific data to construct an image representing the data, and
secondly between the observative and the theoretical models of a
given object. To each of the resulting three main categories corresponds
a different degree of autonomy of the image: ranging from the total
dependence from the real object of images such as photos (or other
kinds of -graphs and -grams), to the perfect indipendence of the
figures of geometry. In the von Koch line hereunder used as the
site map, the three sections are visualised with a different color.
Each of the three sections are subsequently divided into three subsections.
Each of the nine subsections is in turn a link to a page where the
pictures issued by the imaging techiques corresponding to that category
can be found.