In this article I provide a historical-critical inquiry into Simondon's work about the invention and the production of perceptive forms provided with informational potential, thus underlining the effects of undetermined factors during the process of perception. According to Simondon, during the operation of perception, perceptive images/forms are invented especially thanks to elements that cannot be reduced to a principle of order and simplicity. From this perspective, perceptive images or perceptive forms (these two terms are used by Simondon in a synonymic way) are not only the simple product of the application of innate and determined schemes: they are, on the contrary, an inventive result including "undetermined" elements. This can be especially observed in the case of the long duration perception of a turning linear object, as Simondon notes in his article La perception de la longue durée(1969–1970). Before analysing Simondon's peculiar viewpoint about perception, I analyse Simondonian theory of changes, namely allagmatic, to show his original position and his distance from determinism and pure indeterminism.