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Astrophotography and Sketching >> CCD Imaging & Processing

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Hilmi
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PI noise removal without orange peal new
      #6426887 - 03/24/14 04:28 PM

I have no imaging setup now, which is dangerous as in such instances I actually start resuming normal sleeping hours and I also start to question the sanity of this hobby we call astro-imaging. In an effort to distract myself from such dangerous thoughts I decide to spend this time without a telescope learning how to use the noise reduction algorithms available to me without that horrible horrendous orange peel effect that instantly screams PI.

I have tried both TGVDenoise and ACDNR and with my limited knowledge of mathematics I can't get the noise reduction algorithms to behave.

I want a smooth background without the mottled appearance and I don't have the luxury of spending 100 hours on a single target to achieve it.

Somebody teach me how this works, the way the Pros do it


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NOMH
sage


Reged: 06/26/13

Re: PI noise removal without orange peal new [Re: Hilmi]
      #6427291 - 03/24/14 08:41 PM

Well I'm no pro and have only been using PI for a couple of months, however, I really like ACDNR and I do it in two stages. I look at the object and see where the noise is and adjust the mask size and strength accordingly. The first pass is with very little protection on the object IF that is what is required. On the first pass I use 1.0 lightness/1.5 chrominance with the lightness mask check box checked. I then do another pass but adjust the mask to get more of the background to show and using settings of 5.0 lightness/5.5 chrominance. I always create a preview window to test the settings and only apply to the image when satisfied.

I find if the background is mottled I need to strengthen the mask to protect the background.

Of course its a bit more complicated than this filled with lots of trial and error but this is a good start.

Harry has a great tutorial also:

http://www.harrysastroshed.com/pixuser/acnr.html

JB


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: PI noise removal without orange peal new [Re: Hilmi]
      #6427554 - 03/24/14 10:59 PM

If the noise is in the background sky, ATROUS wavelets can help.

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bluedandelion
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Re: PI noise removal without orange peal new [Re: JJK]
      #6427717 - 03/25/14 01:00 AM

TGVDenoise is the best tool. Works on linear and non-linear images. Here's a tutorial from Warren and Rogelio:
http://pixinsight.com/forum/index.php?topic=5829.0

As with everything in PI a little experimentation is necessary. The first couple of images may take a little while. Save the process icons and then use those as starting points for future images.

Also see thi spost for another example:
http://pixinsight.com/forum/index.php?topic=5612.0


Cheers,
Ajay


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Hilmi
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Re: PI noise removal without orange peal new [Re: bluedandelion]
      #6427756 - 03/25/14 01:46 AM

Looking at those images, I would say these denoise procedures need a relatively clean image to start with. So the way I see it, they are of limited utility if you are taking your images from light polluted skies and thus starting off with noisy images. I feel in such situations, a Gaussian blur on the darker areas does a better job

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hytham
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Reged: 12/25/12

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Re: PI noise removal without orange peal new [Re: Hilmi]
      #6427769 - 03/25/14 02:12 AM

As mentioned AtrousWavelets is an awesome tool that will allow you to apply noise reduction to each layer independently giving you more control over the structures in each layer. As you move up the layers, reduce the threshold and adjust the amount accordingly. I tend to leave the iterations to 1, but noisier images will require an increase. Use previews ... heavily.

If using ACDNR, I NEVER apply a single iteration with parameters set to be aggressive. I use multiple iterations with a reduction on the StdDev, and Amount settings. I find this helps to control the noise reduction avoiding that orange peel/blotchy effect.

I'm still deciding on how much I like TGVDenoise. I was a huge fan in the beginning, but not so sure now. I'm sure my lack of experience with it is to blame.

There is another trick to help smoothen out your background is by adding noise. Yeah ... add noise. I have played with this only a little bit against some of my old DSLR images for experimentation. I create a luminance mask, apply it to expose the background and protecting all high signal areas. Apply a Gaussian distribution adjusting the amount accordingly. It provides a nice uniform background to play with and then you can use TGV, ACDNR, or Atrous to smoothen it out.

With all honesty, the best way to decrease your reliance on noise reduction is to capture more exposures.

Just my humble .02.


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Hilmi
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Loc: Muscat, Sultanate of Oman
Re: PI noise removal without orange peal new [Re: hytham]
      #6427790 - 03/25/14 02:36 AM

I will give AtrousWavelets a shot. Never heard of it before, PI seems to have endless functions.

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Puck Ja
scholastic sledgehammer
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Reged: 11/21/12

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Re: PI noise removal without orange peal new [Re: Hilmi]
      #6428137 - 03/25/14 09:52 AM

I am curious about ATWT and would like to learn more about it. I have been using it to enhance star edges after MorphologicalTransform to reduce star size. Can any one point me to the good tutorial on using ATWT for denoising?

Thanks!


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jerryyyyy
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Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: Puck Ja]
      #6428264 - 03/25/14 11:13 AM

Much of the low level noise (or at least a percentage) can be removed by apply ATWT just to level 1... noise removal. If you do this while you watch on HT you will see the effect. I think this along can get you >50% there. I cannot get the TGVD to work well for me either.

One thing I have tried recently with some success (now this is not supposed to work) is to use the Masked Stretch Script under utilities for 200 iterations and a median set to 0.12 AFTER the image is already stretched. Then I apply the ATWT... then autoset the HT shadows to 0 or 1%.

Whoever said more images are the solution is right... with my new Tak I get images fast. I was just looking at some from last night and indeed the best solution for me is to get a lot and apply the linear interpolation.


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Peter in Reno
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Re: PI noise removal without orange peal new [Re: jerryyyyy]
      #6428281 - 03/25/14 11:21 AM

I use MultiScale Median Transform (MMT) instead of ATWT for noise reduction while image is still linear. I use it right after color calibration and before Histogram Transformation. The procedures are almost 100% identical. I thought MMT is more preferred than ATWT.

Peter


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bluedandelion
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Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: PI noise removal without orange peal new [Re: jerryyyyy]
      #6428298 - 03/25/14 11:28 AM

Jerry is correct. ATWT at the smallest scales will get rid of the orange peel look. Try scales 1-3. Leave out 2 and 3 at first and then add them as you see fit. Work on a preview to save time.

Harry has a nice tutorial on the details. You can follow up with TGV on the non-linear image, if you wish, if noise gets enhanced from stretching.

Ajay


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jerryyyyy
Pooh-Bah


Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: bluedandelion]
      #6428444 - 03/25/14 01:02 PM

Quote:

Jerry is correct. ATWT at the smallest scales will get rid of the orange peel look. Try scales 1-3. Leave out 2 and 3 at first and then add them as you see fit. Work on a preview to save time.

Harry has a nice tutorial on the details. You can follow up with TGV on the non-linear image, if you wish, if noise gets enhanced from stretching.

Ajay




This was processed in 10 minutes using these steps (well maybe 12 minutes):



1. Subframe Selector
2. BatchPreprocessing
3. Dynamic crop to clean edges
4. DBE on each image
5. LRGB Combo at defaults no noise reduction
6. Convert to non-linear using default STF and HT settings
7. MaskedStretch script to 0.12 median 200 iterations
8. ATWT level 1 noise removal to RGB and L images
9. Clip RGB to 1% and L to 0% (more noise in RGB)
10. AIP LRGB Combo multichannel synthesis script L at 40% and RGB at 20%
11. Convert to jpg in PI.


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pfile
Post Laureate


Reged: 06/14/09

Re: PI noise removal without orange peal new [Re: jerryyyyy]
      #6429319 - 03/25/14 10:54 PM

i noticed in the PI forum that Alejandro Tombolini used the k-sigma thresholding feature of ATWT to smooth the background of an image. i did not know about that feature and it had a pretty dramatic effect:

http://pixinsight.com/forum/index.php?topic=6870.msg46466

i am not sure if you have to increase the number of layers as he has or not. the k-sigma noise thresholding does not seem to be a per-layer control, but global.

rob


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jerryyyyy
Pooh-Bah


Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: pfile]
      #6430016 - 03/26/14 10:50 AM

Quite an amazing processing tutorial. I had to print it out to read what he was doing. End result is impressive. He uses procedures I never heard of.

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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: PI noise removal without orange peal new [Re: jerryyyyy]
      #6430129 - 03/26/14 11:54 AM

I don't have noise anymore after using TGVDenoise linearly... I run deconvolution, then I turn TGVdenoise afterwards and it seems to clean things up pretty good. I do the heavy stretch mask, local support via the STF, and I get a clean background.

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jerryyyyy
Pooh-Bah


Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: Raginar]
      #6430146 - 03/26/14 12:09 PM

You are running TGVD in non-linear after the deconvolution? What settings are you using for TGVD? I can never get it right. I get that Orange Peel.

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harry page 1
sage


Reged: 07/25/09

Re: PI noise removal without orange peal new [Re: jerryyyyy]
      #6430692 - 03/26/14 04:44 PM

Hi
Here is my view on tgv denoise

http://harrysastroshed.com/TGV.html


See what you think

Harry

Edited by harry page 1 (03/26/14 04:46 PM)


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jerryyyyy
Pooh-Bah


Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: harry page 1]
      #6430886 - 03/26/14 06:30 PM

Thanks, the tutorial mentioned above gives a whole set of new settings for TGVD... I have never felt I have gotten the settings right. Will check your tutorial out.

But, in doing the other tutorial (slow day at work today) it use a Proc that I do not know.

GAMMA STRETCH

Anyone know where that comes from? renamed?


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pfile
Post Laureate


Reged: 06/14/09

Re: PI noise removal without orange peal [Re: jerryyyyy]
      #6431241 - 03/26/14 09:36 PM

i think someone answered on the PI forum but this is one of carlos' modules. they are available on his website at http://www.astrophoto.cl/Research.html

rob


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jerryyyyy
Pooh-Bah


Reged: 10/06/11

Loc: Stanford, California
Re: PI noise removal without orange peal new [Re: pfile]
      #6432709 - 03/27/14 04:58 PM

I followed the new background flattening procedures from the new PI website:

http://pixinsight.com.ar/en/info/processing-examples/13/m-97-owl-nebula.html

to the letter and for sure the background is flatter and darker. Not sure the image is any better...



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