Stock photography involves the supplying of photographs licensed for specific uses. The photographer's photos are marketed to buyers who need them for catalogs, books, magazines, ads, or a variety of other uses. Images are filed at an agency that negotiates licensing fees on the photographer's behalf in exchange for a percentage. Pricing is determined by size of audience or readership, how long the image is to be used, the country or region where the images will be used and whether royalties are due to the image creator or owner.