Using the theme of Currency to invite reflection on the contemporary power of the photograph to relay and relate meaning across distance, the Triennial of Photography Hamburg explores the value of photography in the 21st century. The extension of this economic term to art and visual culture allows for a sustained engagement with photography and its relationship to value-making, canon-making, access, circulation, and knowledge production. At a time when the production, distribution, and consumption of photographic images has become ubiquitous and we have learned to structure our contemporary world through a lens, the digital image has become the currency of exchange on social platforms. Fostering interdisciplinary dialogue, the Critical Reader Lucid Knowledge: The Currency of the Photographic Image gathers international perspectives that reflect on how photography shapes today's narratives, as well as our perception and experience of the world.