Auras when exporting to smaller size

[josed66360387]

I am working with some photos i took at night, when exporting to a smaller size (than the original), this marks appear on the sky. Source files are D750 RAW, i tried seveal exporting settings and have no luck.

Do you have any idea how to get rid of this problem? thanks.

some photos:

and google drive link:

Muestras - Google Drive

thanks in advance.

[Rob_Cullen · Accepted solution]

I think you are seeing "Banding" that is typical in JPG images when tonal compression changes from the 12-14 bit (16) image to the 8-bit image (regardless of the "quality" setting). Often more noticeable on areas like skies where the tones in the original change very smoothly.

For an excellent link on JPG compression go to- Jeffrey Friedl's Blog » An Analysis of Lightroom JPEG Export Quality Settings

Editing the image to introduce grain or noise to the areas that show banding is sometimes used as a fix.

https://www.slrlounge.com/remove-banding-photoshop/

[josed66360387]

You are awesome, thanks for the help.