The Sony HVL-F20M External Flash is an on-camera flash that supports the use of the Sony Alpha TTL system and is compatible with Sony's Multi Interface shoe. When compared to the built-in pop-up flash of many cameras, this flash helps to extend the effective flash working distance by providing a guide number of 65.6' / 20m at ISO 100. Additionally, this flash can serve as a wireless controller for triggering an off-camera flash. For controlling the flash exposure the Advanced Distance Integration (ADI) flash metering system works in collaboration with Alpha cameras and lenses that feature an integrated distance encoder to intelligently produce balanced results. By accounting for the subject-to-camera distance, as well as ambient light and subject reflectivity, the ADI system works to control the flash output in order to provide precise, consistent flash exposures. A built-in diffuser helps to control the spread of the flash; when enabled the spread is wider to suit working with wide-angle lenses, and when disabled the flash beam is narrower and longer to benefit working with telephoto lenses. Additionally, the head can tilt between 0-75