RAW files are considered to be the “digital negatives” for digital cameras. High-end cameras offer the option of saving images in unprocessed RAW format. RAW is analogous to negatives or slides in the analog world. Each manufacturer uses its own RAW format, which can even vary among a manufacturer’s different models.

With film scanners, it is a bit more complicated. Good scanning software also offers RAW as an option, but the type of RAW format depends on the combination of film scanner and scanning software. There is a big difference, for example, between generating RAW files from a Nikon scanner with Nikon Scan or with VueScan. Furthermore, if you have selected correction techniques such as Digital ICE before the scan, such corrections will be permanently applied to the image. Therefore, the meaning of a “digital negative” is not so clear when it comes to film scanners. The definition of a digital negative needs to be extended in comparison to digital cameras. The digital negative is the source file upon which all further processing steps are based. It must never be modified unless the processing steps are reversible.

Analog originals (slides or negatives) must go through a film scanner to become image files. This is where analog to digital conversion occurs. A file is generated from the analog original. Inevitably some image information gets lost in the process. During scanning, the goal is to extract as much image information as possible from the original and save it as a digital negative: the master file. Only then can the best image quality be achieved in post-processing. If any modifications to the image information contained in the digital negative are irreversible, the image would have to be rescanned to restore the original master file.

RAW comes closest to an ideal digital negative. If the scanning software does not allow you to save in RAW, you can use another lossless format such as TIFF as your digital negative. Whichever format is used, it is important that the full extent of the image information obtained with the scanner is preserved in the file.

Image files are easily corrupted, and in most cases this happens accidentally by the user! Unlike an analog negative, the image file can be quickly and easily modified, and image information will be subsequently lost. If, for example, you crop a TIFF file and save it to a file with the same name, the cropped portions of the original image are gone. Nikon Capture Editor handles this situation better than most with Nikon Electronic Format (NEF): the selected crop is saved in a configuration file as opposed to an image file without changing the underlying image. This allows one to revert to full image size later if necessary.

Conventional image editors offer less controlled access when working with an image file. For example, when working with Photoshop, one usually works on different copies of a file to avoid losses. With the right plug-in, Photoshop can open RAW files, including Nikon Camera NEF files, but modifications to an image can only be saved in a different format, such as TIFF. In this case, the digital negative - the master file – remains intact. If your source file is TIFF, on the other hand, the editor can overwrite the original with a modified version and permanently discard cropped borders. Therefore, modifications should be saved as copies, even though this costs additional storage space and can make it more difficult to keep track of versions.

It is more elegant to edit images at the RAW level, the way Nikon does it with the Capture NX2 Editor. All editing steps are saved to a configuration file and can be undone completely or individually. There is no need for an additional work-in-progress copy. There is also no risk of losing image information by editing. This is a truly nondestructive workflow. Any change is fully reversible.

However, editing at RAW level cannot yet offer all of the powerful functions available in Photoshop. Functions such as layers, retouching, or filters are generally not supported with RAW editing programs. Hence, RAW editors are less suited for creative image editing. And that did not really change with the introduction of Nikon Capture NX2 editor which has at least some of this features implemented. Although Photoshop does have functions similar to adjustment layers, image handling with Photoshop cannot compete with Capture NX2. For each correction (e.g., levels, curves, or color balance), a new layer must be created, and seemingly simple operations like reversible cropping are not possible. All in all, you have to use RAW editors and Photoshop in parallel to get full advantage for processing your pictures.