Abstract

Digital pictures can be type-identical in respect of colours, shapes and sizes (allographic), but they are not tokens of notational systems, because the types under which they are identical have vague limits and do not meet the requirements for notational characters. Digital display devices are designed to instantiate only limited ranges of objective properties (light intensities, sizes and shapes). Those ranges keep differences in objective magnitudes below sensory discrimination thresholds, and thus define objective conditions sufficient, but not necessary, for the phenomenal type-identity of pictures. The fact that digital pictures are types shows that pictures are not necessarily autographic. Moreover, the reasons why digital pictures are allographic (essentially, the consistent manipulation of sub-phenomenal information) could in principle also be made to apply to non-digital pictures.