The Nikon D600 raw format is .NEF (Nikon Electronic Format). Every new Nikon camera model, including the D600, has a different .NEF format. The Nikon NEF file contains direct output from the camera sensor and camera specific settings. This requires that any program that reads the Nikon RAW .NEF format be updated to include the camera-specific information. If you try to open the NEF using a program made before the D600 was released, it will not be able to read the .NEF file. You can either update your program to a new version, or use a converter to change the format.
To open Nikon D600 RAW files (.NEF) directly you can use Adobe Photoshop Lightroom 5 or Adobe Photoshop Lightroom 4.2 or newer. Older versions of Lightroom will not read the new D600 .NEF files. There are no updates to previous branches of Lightroom (version 3), you must upgrade to version 4.2 or newer. Version 4.2 offers preliminary support, Version 4.3 and above offers full D600 support.
You can open D600 NEF files with Adobe Photoshop CS6, provided you have updated Adobe Camera RAW to version 7.2 or newer. Earlier versions of Photoshop (CS5 and older) can not be updated to Camera Raw 7.2 and will not open Nikon the D600 .NEF files directly. ACR Version 7.2 offers preliminary support for D600, while version 7.3 offers full support for the Nikon D600.
You can convert D600 NEF files to .DNG using Adobe DNG Converter and then open the .DNG files with earlier versions of Photoshop. You can also open these converted .DNG files with other programs that support the format. Version 7.2 can open D600 NEF files, but version 7.3 is the first to officially offer full support for the Nikon D600.
DO NOT USE the Nikon Transfer program to copy the images to your computer. This program is known to corrupt the NEF files and you may have problems opening and editing the files. Use your operating system to copy files, or copy/open them directly using Adobe Lightroom or View NX2. If you have previously copied NEF files using Nikon Transfer and have problems, you can fix them using this tool.
The Nikon D600 RAW format .NEF files can be opened using current Nikon software. You can use Nikon ViewNX2 software to open the D600 RAW files and perform basic editing. You can also save the D600 NEF files as TIFF and open in the editor of your choice. Nikon ViewNX2 is included with the camera, but you can also download the latest version free from Nikon.
You can also open and edit D600 .NEF files using CaptureNX2 version 2.3.4. Capture NX2 allows advanced editing and features 64-bit compatibility with modern operating systems. CaptureNX2 is commerical software. If you already own CaptureNX2 you can upgrade, or you can buy the full version, or download the demo and try it for 60-days.