Yes, that’s right. Convert JPG to RAW.
In my workshops, I show how it is possible to do this using Nikon Capture NX2 as well other software packages such as Lightroom and Aperture. I want to state up front that what I describe here isn’t truly creating a RAW file from a JPG. Rather, it is converting the JPG into a file that allows you to make nondestructive changes to it. Fundamentally, what you are doing is taking a JPG, which is a lossy file format, and bringing it into a new architecture that makes it a lossless format.
After you convert the JPG into a RAW, it still remains at 8-bits per color channel, versus 12 bit, 14 bit or 16 bit per color channel for RAW files. Also, even though this conversion doesn’t allow all the flexibility of RAW files such as white balance, it is still a worthwhile process because you’ll be able to make all kinds of changes to the image without recompressing it each time you save your changes.
How it Works
I use Nikon Capture NX2 and Adobe Lightroom in my workflow, so I’ll talk about both of them here.
In the case of Nikon Capture NX2, open up a JPG photo that was taken by any camera. Make any changes you want to it such as New Steps, Color Control Points, Hue, Saturation, Nik Color Efex Pro filters or anything else. Then, save the file as a NEF/NRW. The acronym NEF stands for Nikon Electronic Format and NRW stands for Nikon Raw.
This action takes the JPG and then writes the settings into an instruction set that only Nikon Capture NX2 can read. If you open the image in Nikon Capture NX2 in the future, then you can change or modify all the adjustments previously make inside NX2. If you want to remove an adjustment or even perhaps convert the image to black and white, then you simply make those changes with no detrimental effects on the image. After you are finished working on the image, if you save it again as a NEF, then the save is nondestructive. You don’t degrade the original JPG image because you are actually just saving instructions for Capture NX2 to read.
Lightroom (and Aperture) work in a similar, but slightly different way. If you import a JPG image into Lightroom, then make a bunch of changes, it saves the instruction set with the original JPG as a sidecar file. This sidecar is called an XMP file and all the instructions are encoded here for future use in Lightroom.
What I described above does not apply to Photoshop. For example, let’s say you open a JPG in Photoshop and make changes to it. If you save that JPG over itself, then the changes are applied directly to the file AND you will recompress the data. Therefore, this action is a “lossy” save and will degrade your image (albeit slightly) over time. My recommendation for working in Photoshop is to use the Save As command so you keep your original JPG untouched.
One more point I want to make here regarding this idea of converting your JPG into a “RAW” file. This conversion is only visible inside the original host program. In other words, if you convert your JPG into a NEF inside Nikon Capture NX2, then try to open your new NEF inside Lightroom, you won’t see any of your NX2 changes. This is because Lightroom uses different instruction sets than NX2. In fact, neither program can use the other program’s instructions. Kind of a bummer, but that’s the current reality.