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Adjusting the alpha value based on color

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Hello, i've been working with PdN for a while, and now im mostly using it to combine/touch up renders, im going to get more into creating with it soon. So my question is; I have an image, and i want the black in the image to be more transparent, like around a sun, it would gradually fade from light>transparent, not suddenly shifting, I cant find this explained anywhere. If requested I will post the images, but they are quite large filesize, so it would take a good amount of time to upload.

Thank you for your time


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Use the advanced option of curves+.

Input - Luminosity

Output - Alpha.

Then leave the rest as it is, and hit OK.

for the area you highlighted (or the whole picture), luminosity (brightness) will now = alpha.

You can play around with it and fine tune it as well.


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