NEF (Nikon Electronic Format) is the raw image format exclusively used by Nikon cameras. It stores the raw sensor data along with an instruction set for how the image was processed in-camera. NEF files maintain 12-bit or 14-bit data, allowing for extensive adjustments to exposure and color without degrading image quality. Sample NEF files are essential for testing Nikon camera support. Developers use them to verify accurate rendering of Nikon's raw data and to test the handling of proprietary metadata fields like lens information and active D-lighting settings. They are also used to benchmark raw decoding performance.