A method, system, and computer-readable storage medium are disclosed for determining focal lengths of photographs. Image content is displayed in a graphical user interface. The image content is derived from a photograph taken with a lens having a focal length. The focal length is unknown when the image content is initially displayed. A user interface control is displayed in the graphical user interface. The user interface control is displayed on or proximate to the image content. User input comprising a change in position of the user interface control is received. The focal length is determined based on the change in position of the user interface control.