Selective Contrast

[Nigel Ball]

Evening all

Well I decided to process my latest Ha subs of NGC7000/Pelican entirely in PI.

So far so good but I've now hit a problem or rather a gap in my knowledge

When I used to use CS4 I used the Lasso and then Imade/Adjustments/Contrast&Brightness to tease out htos faint areas of nebulosity

How would I go about this in PI

Thanks in advance

Nigel

[Jack Harvey]

Not sure this will work in PI.  The general philosophy is to avoid selecting parts of the image for selective enhancement.  I doubt such a tool is on Juan's list, but I could be wrong.

Hqve you tried using the Dark Structure Enhance script.  It is in Scripts> Utilities.  Be sure to check the box that makes the mask so you will have the mask to operate on using curves or histogram.  I run the script and then undo the result on the image so I can adjust the mask and apply it then use curves or histogram on the masked image.  Hope that makes sense.  Sometimes just running the script will produce the desired result.

[Carlos Milovic]

Not exactly the answer for your question, but I want to write a process that enhances contrast locally. The algorithm is called Adaptative Histogram Equalization. At first, it will be a very naive implementation, but your thoughs are highly wellcome to make this more useful I'll keep you informed

[Nigel Ball]

Have you tried using the Dark Structure Enhance script.  

Thanks Jack

I ran this Script a few times with a different parameters and it does seem to bring out some of the faint stuff

Nigel

[Nocturnal]

I used it on my CA Nebula. In my experience it does not increase detail perse but it does darken the dark areas, as the name implies. The effect is subtle, which is good.