I have a shot here that illustrates very clearly the point I'm trying to make. It's a timed animated GIF file. It will flip after a couple of seconds. There's nothing flash about this pic. It's a failed attempt to do some Ha from my light polluted backyard on the Xmas tree/cone nebula.
Never happened. Not one for the burbs. Too faint. Anyway I had a crack at it using that star removal method. Have a quick look at the before and after shot. Even if you tweak the levels in the original I started from you’ll see that it’s hard to get the contrast of the final. It obviously has some sharpening artifacts as the data was so poor to start with but you can see the technique has its advantages because without the stars in the way you can focus your processing on the nebulosity. It's easier from a user's point of view.
The after looks fantastic. Great result. You use that astro anarchy guy's technique? His PS actions?
I used a bit of the steps that were recorded in the actions combined with some other techniques in the tutorials for the tone mapping. Namely removing the stars with multiple iterations of the dust and scratches filter in PS with decreasing parameters each pass, then overlaying the original as a darken blend to put back the dark bits you might have left behind without putting the stars back in. Then what I really like is the difference blending between the starless version and the original to get the stars only. That's genius. With the appropriate Threshold and colour range selection and proper feathering on the selection you can truly isolate every single spec in the picture and move it to a separate star layer. Once you got that right you're 99% there. The rest is just standard stuff. When you're done you blend the stars back in with a lighten mode or other to suit your taste. I tried screen, pin light. Depends on the picture. I now also use the difference layer trick to isolate clipping in stars or nebulosity so I can then tweak the highlights back down. I did that on the tip of the cone and also on the planetary top right. Very very cool.
Here's a link to the procedure I used as a few people showed some interest. This should give you a base to start from and an idea of the processing flow. Feel free to add your own stuff and experiment. That's what it's all about.
Hi Marc,
Great technique!!! I do not fully understand what you are doing with Noiseware. Are you just doing a noise clean up, or are you doing something else?
Thanks!
I do not fully understand what you are doing with Noiseware. Are you just doing a noise clean up, or are you doing something else?
Hi Gray. Just basic noise reduction. I like noiseware because it's subtle and has loads of parameters. John Glossop put me on it years ago (JohnG). Never looked back. It can sharpen also if you choose to but I turn that to the minimum. I also have noise ninja That Greg Bradley uses a lot and neatimage. They all do things differently and are good to have to.
Last edited by multiweb; 10-06-2010 at 09:16 AM.
Reason: clarification
Out of interest, what settings did you use in noiseware?
What's on the snapshot (10% max). Depends on the picture or layer I'm working on at the time. I usually blink between before/after and do very small incremental passes. I also never sharpen while doing noise reduction. Highpass filter will always introduce noise so I do a noise reduction prior and after also.
There's only that many noise reductions you can do on a pic before starting to see artifacts so the idea is to "spread it" over multiple stages within your processing if that makes sense. If you blow the budget too early or too late it's no good.
G'day Marc, sorry about the thread resurrection. Was playing around on the weekend with some old data, looking at star removal etc. Came back to this thread, followed your method pretty much and it was all very clear. Even made an action for the star removal so it's kinda one click now. Refer attached Oh yeah, go the ED80.
Question time...
Adding the stars back in! I'm ending up with halos of dark around the stars because the starless nebula is stretched I guess. Got any tips/tricks on that one? Also finding the stars look a bit wrong, kinda too small. I don't want to blow them out, but they don't look proportionate to the nebulosity if that makes sense.
That's like some kind of surrealist art. Beautiful work, Troy. Print that and hang on wall.
I've found processing this object to be a pain in the arse. It's got a very limited dynamic range to work with in the nebulosity itself.
I captured this for 2 hours at Snake Valley this year (it was somewhat low in the sky), but, I might need to remove the stars and see if I can turn it into a work of art such as you have here. I doubt it, though, I was imaging with the 40D with the 127ED at 952mm focal length. A bit too in your face, whereas this has the much needed empty space around it.
Adding the stars back in! I'm ending up with halos of dark around the stars because the starless nebula is stretched I guess. Got any tips/tricks on that one? Also finding the stars look a bit wrong, kinda too small. I don't want to blow them out, but they don't look proportionate to the nebulosity if that makes sense.
When adding the stars back in, try adding them as a separate layer on top of the nebula and setting the star layer's blend mode to 'Lighten'. That way only the portion of the layer that is lighter than the underlying layer is added in. Before doing that you can try sharpening the stars, and/or adjusting levels & curves for them if you think they don't quite fit the appearance of the stretched nebula.
Adding the stars back in! I'm ending up with halos of dark around the stars because the starless nebula is stretched I guess. Got any tips/tricks on that one? Also finding the stars look a bit wrong, kinda too small. I don't want to blow them out, but they don't look proportionate to the nebulosity if that makes sense.
The star layer should be set as lighten or lighter color so you don't get black ringing. Another trick is to select the stars with eyedropper and colour range then do a slight shadow/highlight filter on them. That gets rid of black outline. I use that per channel some time on blue channel when doing RGB.
If the stars are too small then the original selection was too tight. Try to increase the expand to 4px and feather more so you have more area to play with and blend in around the stars.
Oh yeah, go the ED80.
