It would have been best if you post the TIFF file (upload it somewhere). Without it, my best guess is this:
data = Import["file.tiff", "Data"] will import the integers stored in the TIFF. These may have various ranges depending of the type of TIFF file. For an 8-bit one, you'll get values between 0..255, for a 16-bit one between 0..65535, etc.
data only has the raw data from the image file without any meta information such as what range of values should be assumed.
Image[data] thus assumed a default range of 0..1 and creates a
Real type image (
ImageType). Thus in your case you should manually specify the type of image you want to create, e.g.
Image[data, "Bit16"] as
dcraw outputs 16-bit files with the
If you want to import the data as an image, just use
Import["file.tiff"]. Also note that since version 10.1 Mathematica can import NEF files directly, without any help from