How to Convert NEF to JPEG on a Mac
NEF is the format for RAW image files shot on a Nikon camera. This format is incompatible with many types of software. For example, any version of Photoshop prior to CS5 cannot open or convert an NEF file, and neither can Aperture on your Mac. However, Nikon provides free software, Nikon ViewNX, for Mac OS X that lets you easily convert your NEF files to the more common JPEG format.
Navigate to Nikon's website and download a free copy of ViewNX for Mac OS X (see Resources).
Drop the application icon into your "Applications" folder after the download is complete. Double-click the "ViewNX" icon to open the application.
Click the "Folders" tab in the left toolbar of the application. Locate the folder containing the NEF images you want to convert and click to select it.
Select the images you want to convert to JPEGs. Click a single image to select it. To select multiply images in a row, click the first image and click the last image while holding the "Shift" key. To select multiple nonconsecutive images, hold the "Command" key while clicking each image icon.
Click the "Convert" button in the top-left corner of the ViewNX application window.
Click the tab next to "File Format" and then select "JPEG." ViewNX automatically saves your JPEG file in the same folder as your NEF file unless you specify another destination.
Click the "Convert" button to convert your images. The conversion process can take 30 minutes or more if you are converting several hundred images.