Photography in the boundaries of the visible. From Santiago Ramón y Cajal to Cecil Frank Powell

In this article, we analyze the use of photographic technologies of two renowned researchers whose investigation results would have been impossible to carry out, as occurs in Galileo a few centuries before with the use of imaging techniques, without the use of photography: Santiago Ramón y Cajal and Cecil Frank Powell, Nobel Prize winners in medicine in 1906 and in physics in 1950, respectively. These researchers were selected, first, because of their close relation with photography and, second, to clearly illustrate the gradual transgression of scientific photographic representation starting in the late nineteenth century from the visible to the invisible