Blacm Halo around stars

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dbbcedt

New member
Aloha
I created a starless background and a star mask. Processed both separetaly and now I am trying to combine them back together, however I cannot get rid of a black halo around the stars (looks like a drop shadow).
I have tried pixelmath both way: background+stars, and max(background,stars). But to no avail.
Any suggestions greatly appreciated.
mahalo
 
Aloha
Yes this is much better, thank you. I will adopt this method, but I also saw that in the process of separating the stars to the background it leave darker area where some of the stars were, so I had to clone stamp it to even the background. But I am very happy with you pixel math method.
Mahalo
 
pfile said:
try ~(~stars*~starless_image)
Click to expand...

Is that for stretched or linear or both?

Why does that work?

I think I follow that it ends up being (stars + starless + stars * starless), and I get that the last term would add some more brightness in the middle area (whatever that means), but I thought starnless masks from starnet were supposed to be exactly the difference?
 
i am not sure if it works for linear frames, i don't think i've ever tried it, but it should work i think...

i think it works out to stars + starless - stars*starless, right?

1 - ((1 - stars) * (1 - starless))
1 - (1 - starless - stars + stars*starless)
1 - 1 + starless + stars - stars*starless)
starless + stars - stars*starless.

so i think it is removing some brightness. the idea being that the color of the nebula was never "behind" the star since it's in front of the nebula. but now you've filled in where the star was with some made up nebula color, and when you are adding back the stars you need to subtract that. i suppose if you are adding back a completely unprocessed star image it is correct without this term, but if you are trying to put in RGB stars that came from another image you need to knock down the fake nebula background before adding the stars over top of it.

rob
 
Thanks for the correction in the last term -- doing math in my head no longer works apparently.

That's even a bit more of a surprise as you would think it darkens an area whereas the original issue was a dark halo. But I'll give it a try.
 
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