DNG (Digital Negative) is a patented, open, lossless raw image format developed by Adobe. It was created to address the issue of proprietary raw formats by providing a single, standard format for archiving raw image data. DNG allows photographers to store their images in a format that is compatible with a wide range of software, ensuring long-term accessibility. Sample DNG files are used to test raw image compatibility across different applications. Developers use them to verify that their software can read generic raw data without needing updates for every new camera model. They are also used to test DNG converters and to ensure that proprietary metadata is correctly preserved when converting from camera-native raw formats.