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The dcraw.exe Software Program




One of the challenges of the Nikon Project is dealing with the RAW files after they are captured. You see, they are monochrome image files saved in a color image format. They haven't been debayered yet, but nearly all image processing programs try to do that as a first step to dealing with the files. Enter dcraw.exe, a program written to specifically deal with RAW image files primarily for high-end digital cameras. The program was written and is available as a free "open source" piece of software written by Dave Coffin. Dcraw can convert RAW files into .tiff format image files compatible with image processing programs. The advantage of dcraw.exe is that it is very flexible and has a number of different options for the conversion process. Most important in this case is the ability to transform the RAW file into a black and white .tiff file without debayering it first.

So, that's the good part of dcraw.exe. It enables us to turn our mono RAW files directly into mono .tiff files. Now we get to the downside of dcraw.exe. It has no normal Windows user interface. Or, actually, any consumer interface at all. I don't think it was really designed for you and me. You access the program and its options from a dos prompt. When was the last time any of us used a dos prompt?

Here is how the program was explained to me. By the way, this is the way you do it in Windows XP. If you have something newer than that, you may have to modify this procedure a bit, or maybe not, I don't really know... You create a file folder on your harddrive. You can call it anything, I called mine "Nikon." In the folder you place a copy of the dcraw.exe program and then all of the RAW files you want to transform into mono .tiff files. You start a dos session. You do this by clicking on "Start" and then "Run..." from the Windows desktop and then type "cmd" in the box. In Windows XP, this opens up a dos box like the one pictured below. At the prompt, type "cd\Nikon" if you named your folder as I did (gee, I even remembered an old dos command). If you named your folder DCRAW, then type "cd\DCRAW" instead. OK? The command to start the process is to type at the dos prompt "dcraw -D -T *.nef" and the transformation will begin. The new .tiff files will be saved to the same folder the RAW files were in. Now, to break down that command, "dcraw" calls the program, the" -D" command tells dcraw to "extract an image with the pure RAW data without any demosaicing or scaling applied." The "-T" command tells dcraw that the output should be a .tiff image file. And the "*.nef" command tells dcraw to do this transformation on every .nef file it finds in the folder. As a side note, on my beat-up, old, and slow Pentium desktop running Windows XP, dcraw takes about 5 seconds per image. You can get your own copy of dcraw.exe from a number of sources on the web, just do a Goggle search for dcraw. The image below depicts an actual session in which over a hundred RAW images were transformed into mono .tiff images, ready for aligning, stacking, and further processing.




DosCommands.jpg










 

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