Spaced Out ::

As part of my project exploring the use of kite-based remote sensing I have been using a Nikon D70 to take aerial imagery. Initially I have been shooting images and storing then as RAW mode files. This is an interesting area as, for the D70, the images are initially captured in 12-bit mode (per channel). I was quite surprised by this as I had been expecting 24-bit colour images, with 8-bits for each of the red, green and blue channels. The Nikon is somewhat unusual as it stores then in the proprietary Nikon NEF format; this can be uncompressed or compressed. It would appear that the compressed format (the only one available for the D70) quantises the data down to 9.5-bit, although the dynamic range is maintained.

Anyway, once you have NEF files (or any other RAW mode files) you need to convert them to something that most bits of image processing or remote sensing software can understand. I had initially used Adobe Photoshop, however it applies a shed-load of post-processing to the file (to make it look nice). If you are interested in “raw” pixel values then you need something else. Thankfully DCRAW came to the rescue. This is a command line programme that has reverse-engineered the structure of a whole swathe of commercial RAW files, allowing you to convert them to PSD (Photoshop) or TIFF formats. Usefully for an impatient person like me, RAWDROP has provided a graphical frontend to this. The final result does not look nice, but you do get the raw pixel values to play with.