User:Van der Hoorn/Viking/Filters

Color images of the Viking landers can be generated by using the original .blu, .grn and .red images in the NASA Viking 1 image archive and NASA Viking 2 image archive. Those red, green and blue images don't have the same maximum wavelength as human vision has (see the table below) and thus the generated color images have a different coloring than we would consider 'true color'.

To generate images that are closer to our perception, we can use channel mixing. To create a more or less 'true color' image, do the following:
 * 1) Download the .blu, .grn and .red PDS images from the NASA Viking image archive.
 * 2) Convert those images to a format of your liking (e.g. jpeg, gif, png). You can use Nasaview to convert the PDS images to gif or jpeg.
 * 3) Open the three images in Adobe Photoshop (or some other image editor of your liking).
 * 4) In the channel view, use the 'Merge Channels..." function and select the RGB option. Then apply the correct image to the associated channel.
 * 5) Use the Channel Mixer (Image > Adjustments > Channel Mixer...).
 * 6) Set the Red output channel to Red 70% and Green 30%.
 * 7) Set the Green output channel to Green 50% and Blue 50%.
 * 8) Leave the Blue output channel as it is (Blue 100%).
 * 9) Now your image should have the peak wavelengths in the last column of the table above, which matches the peak wavelengths of human vision quite closely.