Raw images have some problems which are usually corrected by processing.
- They are all grayscale (color pictures are made by registering and compositing
grayscale images that were taken through colored filters).
- They include camera artifacts and blemishes and sections of missing data.
- They have not been pre-selected for quality; many images will be uninteresting.
Vidicon cameras -- 1970's technology used on the Voyagers and the Viking
Orbiters -- have additional problems; they distort the image and add
a hard-to-predict shading factor to the intensities. To allow image processing to
correct for the first problem, the cameras were made with a grid of black dots,
called reseau marks or reseaux, which make viewing the raw image
even harder. For more information, see the introduction to the
PDS documentation.
However, those of us who do image processing are very glad that PDS released images
in raw format. Had they released only processed images, valuable information
that algorithms such as our
super-resolution
algorithm would probably have been discarded.
Therefore, this atlas will mainly be useful to people (such as planetary scientists) who
have a very specific interest in high-resolution images of
particular sites on Mars, or who need unprocessed images.