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Histogram Processing Questions

Astrophotography Beginner
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#1 leisuredrome

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Posted 09 April 2021 - 11:42 AM

I am following this (one of many out there) amazing tutorial on reducing egregious star halos in Pixinsight and it is working great. But it did lead to a couple of questions:

 

Raising the black point and moving the midtones slider seem to have the same visual effect. Clearly they are different, but what's the practical difference for processing in most situations? Why does the tutorial suggest moving the black point slider versus the midtones slider?

 

In order to minimize the halo and make the masked the area of the star halo match its surrounding environment, you manipulate the histogram using the HistogramTransformation tool. The screenshots show dragging the black point slider to the right. Seems to work fine for me. But I can get, to my untrained & unscientific eye, the seemingly same effect by dragging the either slider to the right.

 

Is there a way to be more precise with my histogram manipulation? 

 

I haven't been using this tool or doing photo editing for very long. But I have learned that my visual assessment is downright terrible at best. The truth is in the pixel values. In the star halo case, what values should I sample and insert into the histogram tool to match the surrounding area more accurately?

 

In general, are there any caveats here? 

 

Feel free to tell me to RTFM. Histogram manipulation seem tricky, so getting practical advice is much appreciated. 

 

 


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#2 cybermayberry

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Posted 09 April 2021 - 03:17 PM

https://www.youtube....h?v=LRwPK4UDYPc




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