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The Question of Noise

Astrophotography
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15 replies to this topic

#1 Karlp295

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Posted 30 November 2022 - 02:29 PM

I have become rather obsessed with noise in my images. A summer where I tried to image with my Canon600D modified for astro was difficult as my images were plagued by high levels of noise. I noticed that my sensor was reaching about 7 degrees above ambient according to APT. This meant my sensor was often at about 34 degrees C. My images were really noisy.

 

This prompted me to get a new camera and I ordered the ZWO ASI533 MC PRO hoping that a cooled camera could change things. It has been about three months now that I have used the new camera and noise is much less of a problem!

 

However, I do see that noise is being amplified in my processing workflow. So I ask this question:

 

When in the workflow should noise reduction be done? I think it should be done early on right?

 

Should noise reduction be repeated after the workflow?

 

I currently have three ways at least of reducing noise while processing images in Photoshop.

 

  1. Camera Raw Filter
  2. Astro Flat Pro by Pro digital software
  3. Colormancer Photoshop plugin

 

Any suggestions on when I should reduce noise to minimize it, and which of the above works best for you.

 

Thanks!



#2 Skysmacker

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Posted 30 November 2022 - 02:41 PM

I have nothing technical to offer but I began using RC Astro's NoiseXterminator plug in for Affinity Photo. This Plug-in works for PS as well. 

 

I do my normal workflow and near the final edits (tweaking color, shading, or histogram) in Affinity and run it through this. It's about $60 and well worth it considering all the other $$$ put into this.

 

It has been a very real improvement and just makes them look great!

 

One thing to add: I began putting a lot more time into my datasets recently and this alone helped but wasn't enough to get rid of noise completely. Even after nearly 30hrs on a target. I have heard people here state that, "noise never goes away, it can only be minimized", which is likely the case, however, programs like this Noise X polish them off nicely for the most part. 

 

get.jpg?insecure

 

get.jpg?insecure


Edited by Skysmacker, 30 November 2022 - 02:49 PM.


#3 idclimber

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Posted 30 November 2022 - 02:42 PM

Link a raw integration after stacking and before integration and I will see what NoiseXTerminator in PixInsight can do. 


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#4 Pingu

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Posted 30 November 2022 - 02:59 PM

Being a newb, not sure how useful my input will be but... I perform noise reduction early on while in linear phase. Just as long as you take it easy on curves process, minimal noise should be introduced.

I've recently begun to use ez denoise in PIS and works very well.
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#5 pedxing

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Posted 30 November 2022 - 03:11 PM

I do most of my NR early in the process before stretching. Sometimes I'll do some ACDNR (in Pixinsight) after stretching for some final cleanup if there is noticeable residual noise.

#6 danny1976

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Posted 30 November 2022 - 03:18 PM

Your 533MC has a very small sensor and going to aps-c size will certainly improve things.

 

If you’re using APT you also have access to dithering which reduces/eliminates walking noise.

 

NoiseXTerminator does an amazing job of reducing noise without taking away too much detail. I use it as a plug-in in Photoshop.

 

When using duoband filters noise kicks in very soon. That’s why I try to get a minimum of 20h per target with the L-eXtreme. Without filters on a dark location I was happy with a 2h shot of Andromeda.


Edited by danny1976, 30 November 2022 - 03:48 PM.


#7 jesco_t

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Posted 30 November 2022 - 03:22 PM

The better your gear & technique become and the more integration time you spent on a single target, the noise in processing never really goes away.

Why?

Because more and better data just allows to stretch it harder and reveal more and more details. It’s up to you to decide where to stop. Sometimes this means stopping early and not needing much noise treatment, and sometimes you fight for every little grain of signal.

I think the key is to not overdo it and try to hard. There’s beauty at all depths of the signal.
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#8 kathyastro

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Posted 30 November 2022 - 03:30 PM

A hit of noise reduction is the first thing I do when I open my linear masters.  I might do some more noise reduction later in the processing if it looks like I need it.  But mostly, if I see that I have a lot of noise, I'll shoot some more frames on the next dark night.

 

I did a version of the California nebula last month where the Oiii channel showed nothing but noise after 4 hours, so I omitted it.  Last night, I shot another 5 hours, for a total of 9 hours, and, while there is still some noise, I can see a nice signal in there now.  The best noise reduction technique is more data.


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#9 choward94002

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Posted 30 November 2022 - 03:49 PM

To be really able to manage "noise" you have to look at it for what it is: signal that you just don't want.  Once you read, follow and understand that sentence fragment it becomes much more clear about how to manage it ... and there are entire books written for this that I'd suggest reading (other threads here discuss those)

 

First, you need to eliminate unwanted signal from inside the camera ... that's darks, bias and dithering and in the case of some camera's microlensing

 

Next, you need to eliminate unwanted signal from the imaging train ... that's flats and in the case of filters haloing

 

Finally, you need to eliminate unwanted signal from the outside ... that's various LP filters, narrowband, or even better simply darker skies (as many say)

 

Once that's all done, and you've eliminated all of the unwanted signal that you can from all of the various sources that can generate it then it's time to apply noise reduction and start amplifying the signal ... that's stacking and (in my case) SQM and seeing sorting of the lights

 

There is no "easy" button unfortunately, you can get "easier" by simply using data from the Hubble and JWST, or by renting time on an iTelescope rig, but again no "easy" button ...



#10 Midnight Dan

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Posted 30 November 2022 - 04:18 PM

I have become rather obsessed with noise in my images. A summer where I tried to image with my Canon600D modified for astro was difficult as my images were plagued by high levels of noise. I noticed that my sensor was reaching about 7 degrees above ambient according to APT. This meant my sensor was often at about 34 degrees C. My images were really noisy.

 

This prompted me to get a new camera and I ordered the ZWO ASI533 MC PRO hoping that a cooled camera could change things. It has been about three months now that I have used the new camera and noise is much less of a problem!

 

However, I do see that noise is being amplified in my processing workflow. So I ask this question:

 

When in the workflow should noise reduction be done? I think it should be done early on right?

 

Should noise reduction be repeated after the workflow?

 

I currently have three ways at least of reducing noise while processing images in Photoshop.

 

  1. Camera Raw Filter
  2. Astro Flat Pro by Pro digital software
  3. Colormancer Photoshop plugin

 

Any suggestions on when I should reduce noise to minimize it, and which of the above works best for you.

 

Thanks!

If you are truly obsessed with noise, then the best advice I can give you is to increase your total integration time.  There's simply no substitute for it.  

 

When I started in AP, I would shoot an hour or two on a target and do several targets in a night.  As time went on I started upping my integration time till I got to the point of just shooting one target for the whole night.  Now I spend several nights on a target and I try for a minimum of 10 hours.  My best images have 20 to 30 hours.   I've seen the difference it makes and it is substantial.  When you're trying to pull out those dim details without also pulling out the noise, long integration is the only game in town.

 

That said, I do noise reduction early in processing in the linear phase.  But I always apply more later, near the end.  If you're doing really aggressive stretching and digging deep to pull out the details, it will definitely bring out some of the noise that was missed early on.

 

One more tip.  The interesting thing about noise is that a small amount of it can actually increase the perception of sharpness.  And it gives the image a more "real" look in my opinion. So I try not to reduce the noise to the point where everything looks perfectly smooth like it's made of plastic.

 

-Dan


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#11 ngatel

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Posted 30 November 2022 - 06:52 PM

A hit of noise reduction is the first thing I do when I open my linear masters.  I might do some more noise reduction later in the processing if it looks like I need it.  But mostly, if I see that I have a lot of noise, I'll shoot some more frames on the next dark night.

 

I did a version of the California nebula last month where the Oiii channel showed nothing but noise after 4 hours, so I omitted it.  Last night, I shot another 5 hours, for a total of 9 hours, and, while there is still some noise, I can see a nice signal in there now.  The best noise reduction technique is more data.

Good advice. I now spend more time on each target than I did when I first started. Plus I now usually run two mounts every night.

 

I only have OSC cameras. I use NoiseXTerminator. Early on in a linear state with the stars removed, I extract each channel (R, G, B) and usually do NXT on each. Not a whole lot, just depends on what each channel shows. Then later, after a stretch of the re-combined starless image, I may do additional NR if needed. I find it better to do a little bit of NR a couple times, if not more.


Edited by ngatel, 30 November 2022 - 08:04 PM.


#12 soojooko

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Posted 30 November 2022 - 07:56 PM

I hit the noise reduction the moment I think the image looks noisy.


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#13 TerryD1

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Posted 30 November 2022 - 11:54 PM

I have nothing technical to offer but I began using RC Astro's NoiseXterminator plug in for Affinity Photo. This Plug-in works for PS as well. 

 

I do my normal workflow and near the final edits (tweaking color, shading, or histogram) in Affinity and run it through this. It's about $60 and well worth it considering all the other $$$ put into this.

 

It has been a very real improvement and just makes them look great!

 

One thing to add: I began putting a lot more time into my datasets recently and this alone helped but wasn't enough to get rid of noise completely. Even after nearly 30hrs on a target. I have heard people here state that, "noise never goes away, it can only be minimized", which is likely the case, however, programs like this Noise X polish them off nicely for the most part. 

 

get.jpg?insecure

 

get.jpg?insecure

Not wanting to pay a monthly subscription for Photoshop I just acquired Affinity Photo myself.  Do you perform your stacking in it?


Edited by TerryD1, 30 November 2022 - 11:55 PM.


#14 Karlp295

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Posted 01 December 2022 - 04:47 AM

Not wanting to pay a monthly subscription for Photoshop I just acquired Affinity Photo myself.  Do you perform your stacking in it?

I get Photoshop free and so I use that for post processing. I use Siril for the stacking and subtraction of darks. 



#15 soojooko

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Posted 01 December 2022 - 05:19 AM

Not wanting to pay a monthly subscription for Photoshop I just acquired Affinity Photo myself.  Do you perform your stacking in it?

Another Affinity user here. Unfortunately, the stacking is not great. I've found I get considerably better results using ASTAP to stack. But for post processing, Affinity is a great option.



#16 Skysmacker

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Posted 01 December 2022 - 08:57 AM

Not wanting to pay a monthly subscription for Photoshop I just acquired Affinity Photo myself.  Do you perform your stacking in it?

No, I used SiriL for a couple of years but now use Astro Pixel Processor.




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