Stock photography artists get inspiration everywhere and that includes someone else's great work. But, when is this part of the creative process and when is it considered copying someone else's image and therefore not copyright-able by you? One word most stock photo artists are familiar with is "derivative." According to iStockphoto.com, a derivative work is photos stock that consist of editorial revisions, annotations, elaborations and other modifications, which, as a whole, represent an original work of authorship. These types of artistic works are not copyright-able by you if you created them based on someone else's art.