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Siril Creating Noisy Images

Siril Team Siril Optolong L-eNhance Processing Background Extraction Color Calibration
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Derek Vasselin avatar
Derek Vasselin avatar
I used to process primarily with Photoshop and decided to add Siril to the box of tools.

I typically use Siril to do a background extraction and color calibration. On occasion a few other things like combining the green and blue channels for a better HOO palette (I use a color camera with an Optolong L-Enhance).

I've noticed that with those initial steps in Siril, my images look significantly noisier than if I process only in Photoshop.

I figure at some level, it's just a sign I need more integration. But even the images I have 16 hrs look noisy with Siril and the difference between that and Photoshop only is noticeable.

Is there something simple I'm missing? Or is it just something with Siril itself?
andrea tasselli avatar
andrea tasselli avatar
Not a clear question. What you do, how you do it and post of examples to give some meaningful answer.
Nico Carver avatar
Nico Carver avatar
My guess is you are seeing more noise in Siril because you are stretching it differently than you do in Photoshop. Another possibility is in background extraction. Siril is good at it, but often images look noisier after background extraction because you are removing all the signal of the light pollution gradient but leaving the noise. If it’s light pollution, not much you can do about that other than getting more data. You can control how much noise shows by stretching less aggressively but that also means the photo will be darker and/or have less contrast.

Might be helpful if we could see an image processed with Siril and the same image processed how you would in Photoshop with all the steps in each listed.
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Derek Vasselin avatar
Derek Vasselin avatar
Nico Carver:
Another possibility is in background extraction. Siril is good at it, but often images look noisier after background extraction because you are removing all the signal of the light pollution gradient but leaving the noise.


I think this might be where the difference is coming from. 

I will pull together an example image from each process this afternoon and post with the process details.
Well Written
Charles avatar
Charles avatar
A suggestion.

Use the latest stand alone version of graxpert with their latest AI database, versus using the integrated graxpert bge in siril.
James Peirce avatar
James Peirce avatar
Derek Vasselin:
Nico Carver:
Another possibility is in background extraction. Siril is good at it, but often images look noisier after background extraction because you are removing all the signal of the light pollution gradient but leaving the noise.


I think this might be where the difference is coming from. 

I will pull together an example image from each process this afternoon and post with the process details.

If you haven’t previously been doing a background extraction, that is certainly something to bear in mind. A background extraction *is* a removal of signal, and what is left behind can easily appear to be noisier if you don’t balance it in a similar way with background relative to other tonal ranges.

I’ll second the note about examples. They are *extremely* valuable for giving meaningful feedback in a case like this. For example, usually when someone asks this, they are comparing a much more aggressively stretched image with the background extracted to a less aggressively stretched image without. In some cases because they are comparing before and after with an auto-stretch applied, or in others because they have brought up the signal of faint-signal background up more more aggressively than it would be in any edited image. Other explanations could be relevant, and may not be obvious without examples and an explanation to go along with them.
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AstroGinger avatar
AstroGinger avatar
In a nutshell, I will suggest the following:
  1. Stack your images in SIRIL
  2. Remove gradient and denoise with GraxPert
  3. Back in SIRIL to remove green noise
  4. Then you can do the color correction or use starnet removal
  5. Only at the end of the  process, you can use Photophop for the cosmetics...
kurt ragsdale avatar
kurt ragsdale avatar
I have only been using Siril to remove noise. I use for the most part the data adaptive dual domain denoising tool to reduce the noise. I have found the zwo planetary stacker works alright for stacking multiple sessions with object. I tried using the regular zwo deep sky stacker but it tells me it's got errors with my see star sessions.