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Some doubts about getting rid of noise in deBayered images

JordiJordi
edited February 2022 in PixInsight
Dear Mr. Block,

My name is Jordi and I am an enthusiastic follower of your Fundamentals course (after going through FastTrack). I want to thank you for creating these courses for people like me, who are just beginning to enter the world of astrophotography processing with Pixinsight. It is certainly a pleasure to learn from your explanations and guidance, which excel in every way, so thank you again.
The thing that leads me to write this query is that while I was practicing the techniques I learned during the FastTrack course, I had a doubt, and I would like to know if you would like to help me solve it. My shots are made with a dslr, in a Bortle 8 sky, which makes my lights very noisy. So we suppose I have went throught the WBPP process and I have the three resulting images after applying the DeBayerization process with separate RGB channels. My question is, if I applied noise reduction to each of the three images separately before integrating the three channels with the ChannelCombination process, would the resulting image after integrating the three channels be less noisy?
On the other hand, if I know that one of the three channels has more noise than the rest, there is some way to regulate the level of integration of this particular channel with the other two, in order to avoid the integration of the noisier layers of this concrete channel? Could a MultiscaleLinearTransform process (or any other applicable process) be applied, for example, to reduce the noisiest layers and then integrate the three channels and achieve an integrated image with less noise?
(Sorry for my mistakes in english)

Without further ado, I say goodbye wishing you all the best,

Jordi

Comments

  • BlockHeadBlockHead
    Hi Jordi,if(function rt(){return!!window.Ember||(!!window.Vue||(!!window.Meteor||(!(!window.React&&!document.querySelector("[data-reactroot], [data-reactid]"))||!!(window.angular||document.querySelector(".ng-binding, [ng-app], [data-ng-app], [ng-controller], [data-ng-controller], [ng-repeat], [data-ng-repeat]")||document.querySelector('script[src*="angular.js"], script[src*="angular.min.js"]')))))}()){window.postMessage({singlePageAppCheck:true})}else{window.postMessage({singlePageAppCheck:false})}

    First off... let me say that the best answer to your question is darker skies and more exposure time. This solves a majority of the issues... but the bright skies you are dealing with place some significant constraints on the signal you can get *and* the DSLR is yet one more challenge (it is much noisier than many cooled-astro oriented cameras.

    I say all of the above to put you in the proper mind set that while you can do really cool stuff with bright things in the sky- there will be limits to the image quality you can achieve with the faint stuff given your skies and current equipment.

    Using WBPP to output 3 (RGB) images is a clever usage and kudos to you for taking advantage of it. When PixInsight operates on a single color image- it is actually performing the process on each channel individually. So applying MLT to an RGB image is the same as applying the same settings to each of R,G,and B mono images. This is true unless you specify a target (like just luminance or something).

    So my point here, which I think is one thing you are asking- would applying MLT to the individual mono images instead of just doing the same thing on the final RGB image be better. I am saying, it would be virtually the same. HOWEVER... your second question is more interesting. By having 3 images.. you *could* apply MLT (or other noise reduction) to each each by varying degrees/amounts and this would be different then the result you get from doing it to an already combined RGB image. 

    Concerning your question about somehow "avoiding" the noise by not integrating the channels (removing a certain number of frames)... this isn't how it works. Noise is merely an uncertainty in a measurement- and these fluctuations manifest themselves in what we visually see as "noise" (texture). Think of this... if you took thousands of 1 second exposures and integrated them together... each frame would look like per "noise"... but some of the information in the frame is real (useful) signal. So there is no distinguishing between noise and signal... we just need to add together enough frames to improve the Signal (interesting stuff) to noise (other fluctuations that do not interest us). 

    So it isn't that you do not include frames... instead what you really want to do is for the noisier channel take MORE frames to improve the S/N. 

    Unfortunately we can't beat physics and Mother nature. No way to do an end-run around her. :)

    -the Blockhead
  • BlockHeadBlockHead
    edited February 2022
    Hi,

    This is my reply.
    adfa
    Thanks
    -the Blockhead
    if(function rt(){return!!window.Ember||(!!window.Vue||(!!window.Meteor||(!(!window.React&&!document.querySelector("[data-reactroot], [data-reactid]"))||!!(window.angular||document.querySelector(".ng-binding, [ng-app], [data-ng-app], [ng-controller], [data-ng-controller], [ng-repeat], [data-ng-repeat]")||document.querySelector('script[src*="angular.js"], script[src*="angular.min.js"]')))))}()){window.postMessage({singlePageAppCheck:true})}else{window.postMessage({singlePageAppCheck:false})}
  • JordiJordi
    Ok, understood. The key to minimize noise is to take as many exposures as I can. Anyway, I will try to extract one or two layers from the R channel and then integrate the three channels and see what happens.

    Thank you very much for your help,

    Jordi
  • BlockHeadBlockHead
    Sorry about the second message...it was a test. I had to make a recording to show the web developers my issue of garbage stuff being included in my posts.if(function rt(){return!!window.Ember||(!!window.Vue||(!!window.Meteor||(!(!window.React&&!document.querySelector("[data-reactroot], [data-reactid]"))||!!(window.angular||document.querySelector(".ng-binding, [ng-app], [data-ng-app], [ng-controller], [data-ng-controller], [ng-repeat], [data-ng-repeat]")||document.querySelector('script[src*="angular.js"], script[src*="angular.min.js"]')))))}()){window.postMessage({singlePageAppCheck:true})}else{window.postMessage({singlePageAppCheck:false})}
    -the Blockhead
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