From SO site: This filter was designed with Mars in mind, but will find uses elsewhere as well.
Mars has reddish disks with dark blue and green markings.
This filter emphasizes these two spectral regions by rejecting the very dominant yellow and greenish-yellow regions.Blue-greens and reds will maintain a very high transmission with this filter. Mars will have a magenta color with the darker features sharply defined. This filter is well suited for smaller apertures because the image isn't darkened as much as with many color filters.
As with all contrast enhancement filters, this is not an end-all tool, but will greatly aid in pulling out additional detail from Mars.
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