Choosing the Raw Image Format for a Nikon DSLR
Aside from the default image file type (JPEG), the other picture file type you can create on your Nikon D3100, D5100 or D7000 is Camera Raw, or just Raw (as in uncooked) for short.
Each manufacturer has its own flavor of Raw. Nikon’s is NEF, for Nikon Electronic Format, so you see the three-letter extension NEF at the end of Raw filenames.
Raw is popular with advanced, very demanding photographers, for three reasons:
Greater creative control: With JPEG, internal camera software tweaks your images, adjusting color, exposure, and sharpness as needed to produce the results that Nikon believes its customers prefer. With Raw, the camera simply records the original, unprocessed image data. The photographer then copies the image file to the computer and uses special software known as a Raw converter to produce the actual image, making decisions about color, exposure, and so on at that point. The upshot is that shooting Raw enables you, not the camera, to have the final say on the visual characteristics of your image.
Higher bit depth: Bit depth is a measure of how many distinct color values an image file can contain. JPEG files restrict you to 8 bits each for the red, blue, and green color components, or channels, that make up a digital image, for a total of 24 bits. That translates to roughly 16.7 million possible colors. A Raw file delivers a higher bit count.
Best picture quality: Because Raw doesn’t apply the destructive compression associated with JPEG, you don’t run the risk of the artifacting that can occur with JPEG.
But of course, as with most things in life, Raw isn't without its disadvantages. To wit:
You can’t do much with your pictures until you process them in a Raw converter. You can't share them online, for example, or put them into a text document or multimedia presentation. You can view and print them immediately if you use the free Nikon ViewNX 2 software, but most other photo programs require you to convert the Raw files to a standard format first. Ditto for retail photo printing. So when you shoot Raw, you add to the time you must spend in front of the computer instead of behind the camera lens.
Raw files are larger than JPEGs. Unlike JPEG, Raw doesn’t apply lossy compression to shrink files. In addition, Raw files are always captured at the maximum resolution available on your camera, even if you don’t really need all those pixels. For both reasons, Raw files are significantly larger than JPEGs, so they take up more room on your memory card and on your computer’s hard drive or other picture-storage device.
To get the full benefit of Raw, you need software other than Nikon ViewNX 2. The ViewNX 2 software that ships free with your camera does have a command that enables you to convert Raw files to JPEG or to TIFF, another standard imaging format. However, this free tool gives you limited control over how your original data is translated in terms of color, exposure, and other characteristics. The same is true for the Raw converter built into the camera.
Whether the upside of Raw outweighs the down is a decision that you need to ponder based on your photographic needs, your schedule, and your computer-comfort level.