Unconventional Masking Techniques

[BobinBend]

I am currently working in an image of M100 which has some terrible vignetting issues on the bottom left corner of the image. I know the source of the problem but I'd still like to save this image. Using the Histogram Transformation process I can darken the background sky. But if I darken it to the point of eliminating the vignetting brightness I also loose a lot of the galaxy and faint stars.

Is there a way to mask a portion of the image so I can darken just the vignetting portion without affecting my galaxy?
Thanks,
Bob

[Enzo De Bernardini]

Hi Bob,

Try RangeSelection. You can also create a radial gradient with PixelMath and use it as mask, but this will require some trial and error tests:

• RGB/K = (~max( 0, ( rdist( cx, cy ) / r )))*h
• Symbols: cx=256, cy=256, r=200, h=1.5

References:

• cx, cy = center coordinates
• r = radius
• h = hardness

Process icon attached. Remember create a new image as target, with the same dimensions of your image.

Greetings,

Enzo.

[BobinBend]

Enzo,
Thanks for your help. It worked just like I needed!

Bob