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Arcsinh Stretch Hue Shift?

Wayne Hixson
in PixInsight
I love the use of Arcsinh to maintain color as we stretch the image, but I've run into a couple issues. I did M33 with a OSC camera and extracted the Lum for later integration. I used Arcsinh to stretch  the RGB image and got much stronger colors than with HT, but as I applied it the second and third time, the blues in the image seemed to shift to purple. Using Curves Saturation on a HT stretched image seemed to do better with retaining more blue. Have you run into hue shifts like this?

Also, any suggestions for protecting the brighter stars from color halos during Arcsinh stretching?

Wayne

Comments

  • BlockHeadBlockHead
    Yes, I mention the hue shift in the lesson. At this point, I have been treating ArcSinhStretch as a method for getting color in faint objects (or areas). All of its drawbacks relate to already bright things. In terms of a Hue Shift...I would basically shift it back. In terms of stars- my best solution at this point is to either mask the brightest stars or do a substitution with the original RGB stars (stretched in a normal HT like manner). So mixing and matching is important... no particular process is an all-in-one tool in this case.

    -the Blockhead
  • Scott Iver
    Wild thought...   Since it would seem that Arc effects brighter area's to detriment, what about using something like range selection to mask just the brightest stars when stretching, and to that not mask them at 100% so that the stretch would not be applied as drastically to only those areas?
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