>Hi, all. > >I have a picture of comet 46P/Wirtanen from a few nights ago. > >I'm new to GIMP and it's like a space shuttle control panel to me. > >Can you please provide step-by-step instructions to >1. reduce vignetting in the corners >2. smooth out the background noise >3. keep stars (the brightest ones are already over-saturated) and >comet and approximately the same brightness but make the background >sky darker > >I tried playing with levels picking various black/white/mid points but >wasn't happy with the results. > >I also tried gaussian blur but could not figure out how to apply it to >the photo without bluring the stars. Perhaps some mask needs to be >created to isolate stars and comet so that the gauss filter can be >applied to the rest of the pixels and allow to keep the comet and >stars sharp? > >Thanks!
First a caveat, I would not recognise a comet at 100 metres. Always many ways with Gimp but try: (with screenshots) 1. I would promote the image to 16 bit, might be that already, I see your jpg has a quality setting of 55 to get a smaller file size. Use your best image. https://i.imgur.com/BqFWbsG.jpg 2. Duplicate the layer "Layer -> Duplicate layer" and apply a large gaussian blur to the new layer. "Filters -> Blur -> Gaussian Blur". The value will go above 100, do not be fooled by the sliders. Round about 200 https://i.imgur.com/llKHYQy.jpg 3. Put that blurred layer into "Difference" mode. That will even out the background. https://i.imgur.com/J3lfW0R.jpg 4. Rather than destroying your work combine those layers "Layer -> New From Visible". Apply "Colors-> Levels" to this layer. Use the White point picker and choose one of those larger white-ish stars. https://i.imgur.com/RRFP2iN.jpg 5. Get rid of the smaller stars/junk "Filters -> Generic -> Erode". If you feel it needs it, repeat. https://i.imgur.com/dcNks8Y.jpg Attached a result, again lower quality setting to get the file size down. Might/might not be what you require. Attachments: * http://www.gimpusers.com/system/attachments/1073/original/Comet01.jpg -- rich404 (via www.gimpusers.com/forums) _______________________________________________ gimp-user-list mailing list List address: gimp-user-list@gnome.org List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list List archives: https://mail.gnome.org/archives/gimp-user-list
