Applying BXT as final step in processing [Deep Sky] Processing techniques · Michael J. Mangieri · ... · 27 · 845 · 2

XCalRocketMan 3.71
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I was wondering if an application of BXT to the final image would be beneficial in some instances in improving the detail lurking within an image. Now I understand the science behind the BXT tool (that it should only be used in the linear state since it was trained in that image domain) but I reasoned it might be useful, in some cases, to enhance an image. I did this with my latest capture, M97, Owl with Post BXT, with some rather interesting results. I did set Sharpen Stars to 0.0, unchecked all the options and left Automatic PSF on.

What are your opinions on using this method? Recommended? Not recommended? What were you thinking ?!!? .
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morefield 12.31
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Since BXT is deconvolution I don't believe actual deconvolution is possible on the fully processed image.  Adding contrast at a specific scale could still be done however.  That would really be what has always been called sharpening rather than deconvolution.  There are a number of ways to do that but MMT might be the most common.

Kevin
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andreatax 9.89
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I'm not sure I would call it "interesting", at least in any positive way, I'm afraid. The short answer is: don't. The longer answer is: you can apply unsharp mask to better effect (with provisions) than BXT outside where it is reasonable for it to be applied and still produce realistic results (to a degree).
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KGoodwin 4.71
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No, this is a bad idea.  It will cause artifacts, it isn't trained on non-linear data, and it's just destroying data.  For a final sharpening use something like unsharp mask.
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XCalRocketMan 3.71
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As I expected, this is a bad idea. Thanks for the comments. This is why I didn't post the B revision as the final smile
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AstroTrucker 6.22
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I usually don't chime in on a thread like this. However, looking at the Owl with BXT applied late, I have a few comments on the image. I want to say, I don't know if my comments will apply to the application of BXT but they are observations none the less. 

- looking at the center of the Owl the mid range of the image is washed out and overall has a "flat" look lacking dynamic range
- same can be said of the stars. All seem to be the same intensity and sharp. hard to tell with the JPEG but the stars have a trace of dark ringing
- an application of NXT late would not hurt this image.

I say all of this with peace and love. Many other ways to "sharpen" a starless image late in the workflow b4 screening back in the stars. Also, several ways to reduce stars (size, luminance, etc) without an overuse of BXT. BXT is best used early in the workflow while the image is linear. I do probably as much work on an image linear as I do to it post stretch to non-linear…

CS Tim
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Overcast_Observatory 19.90
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I have experimented with this quite a bit, using BXT as a sharpening tool on non-linear data.  On undersampled data it can sometimes give the illusion that theres more detail in there, but it's really hard to not make it look cooked, and as mentioned above, artifact-free.  At the time it was kind of a novel ideal (for me) and I thought it could be useful, but ultimately I decided that it was doing more harm than good, and no longer use the tool this way.  There are definitely better sharpening methods out there and to be honest, I dont generally sharpen either. I find that a really light application of LHT with something like the settings below can make the details and the image pop a little better.  Gotta be careful with any tool though, it's easy to overcook the image.

LHT.JPG
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Gondola 8.11
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I say don't worry about the "rules". Everyone's data and process is different. This hobby if full of rules that are just heard and passed down as gospel. Do the AB testing, if it benefits your image, do it. It doesn't matter what everyone else thinks.
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KGoodwin 4.71
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Tony Gondola:
I say don't worry about the "rules". Everyone's data and process is different. This hobby if full of rules that are just heard and passed down as gospel. Do the AB testing, if it benefits your image, do it. It doesn't matter what everyone else thinks.

One reason the “rules” exist (as does the RCC forum here) is that we tend to be pretty poor judges of our own images. Beginner to intermediate imagers tend to be especially bad at seeing things in the moment that they easily see after a few days and then being disappointed with the results they posted. It’s sort of like writing where there are “rules” of grammar and style, but great writers know when they can get away with not applying them for some specific purpose.

You could do a lot worse in processing your images than just following the “rules” until you get very good at it. Experimentation is great, but focus it on areas that are more creative and a less firm technical answer. Experiment with palettes and stretches, HDRMT, saturation, soft light, those kinds of things that are creative choices rather than things like “do deconvolution first” which is a “rule” because of good technical reasons.
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azskyguy 0.00
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I use APF-R as a last processing step in an image. I do the main processing in Pixinsight, but finish up in Photoshop. The APF-R software is a Photoshop plug-in, and it usually gives great results. 

Here's some info:

https://petapixel.com/2021/06/11/this-sharpness-boosting-process-is-used-by-hubble-telescope-editors/
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CCDnOES 8.34
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Speaking for myself, I never use BXT on anything but linear images very early in the workflow. That is because, as others have noted, it is designed for linear data and Russ has been very clear on that point.

On the subject of "looking overcooked" that can happen with any deconvolution of any kind at any time. It often results in what is commonly called "threadlike detail".  OTOH, some objects, especially some planetary nebula, actually do have threadlike detail so one has to be careful in assuming that all such detail is a result of "BXT overcooking". My rule is to look at the unconvolved image after giving it a temporary stretch (just to examine it, you do the BXT on unstretched data, of course) and see if there is a hint of such structure. Using the BXT real time preview and blinking it on and off is helpful as well here to see what the enhancement is doing and where. If there is such real detail, then "looking overcooked" may not be actually overcooked and the enhanced structure may be real. A perfect example is Abell 30 that I processed yesterday, which is why this comes to mind. Pretty much all the images of that object show the detail to some degree, even including images from the Chandra X-ray telescope. That leads to another "reality check" and that is professional images of the same object, where available.

The biggest deconvolve error is to use non-astro AI enhancement programs on non-linear astro images. I have seen a small handful of images on AB that have done that and they look nothing short of bizarre. I will be kind and hope the imagers were just being "artistic". 
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whwang 15.16
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Try it, and see if you like it.  It won'y hurt, right?

BXT is based on deconvolution, which only has meaning on linear data.  Our final images are all highly nonlinear.  So in principle this is a bad idea.  In reality, although the overall tone is highly nonlinear, it can still be close enough to being linear within a limited range of brightness.  So it can work on things that do't have super high contrast within a short range (few pixels).  So, just try it.  It may work, or may not.  (Here, "work" means it gives you a sharpening effect without obvious artifacts.  It will never give you a result that's mathematically equivalent to deconvolution.)

I sometimes run BXT on mildly nonlinear data (weakly stretched). I never run BXT on my final image. I rather prefer standard sharpening tools such as unsharp mask for my final images or images that are strongly stretched.  Even on the mildly nonlinear data, BXT can sometimes give me artifacts around the cores of moderately bright stars.  So watch out your stars if you do run BXT on your final image, and don't get too excited by what it does on your nebulas.
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JamesPeirce 2.11
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It used to “kinda” work as a sort of AI sharpening, albeit not as well as when done at a proper stage for deconvolution.

But in an updated model concern for maintaining any degree of performance in stretched images was set aside in favor of optimal performance as a deconvolution tool, and it now can be quite problematic when not used at a proper stage for deconvolution (resulting in strange rendering and hallucination of stars; odd handling of various details, etc.). And so it is recommended not to use it outside those conditions (generally and by the developer). Which is great in my book: it excels at doing what it is meant to do.

Edit: Typos.
Edited ...
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Gondola 8.11
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Mel Martin:
I use APF-R as a last processing step in an image. I do the main processing in Pixinsight, but finish up in Photoshop. The APF-R software is a Photoshop plug-in, and it usually gives great results. 

Here's some info:

https://petapixel.com/2021/06/11/this-sharpness-boosting-process-is-used-by-hubble-telescope-editors/

This looks very much like the synergistic sharpening method that bin member and YouTuber SkyStory uses in his images. Basically, combining sharpening at different image scales or frequencies to get a controlled and balanced result.
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azskyguy 0.00
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It works very well on the great majority of my images. It's apparently popular with the Hubble team. And it's reasonably priced. I would not want to be without it.
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Gondola 8.11
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No doubt it's a good tool and I like the price but it does require PhotoShop and that's another whole subject!
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Stefek 3.81
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It is a free world, so everyone can try whatever makes him happy  with his image. However , i think in our hobby we should pay some respect also to the nature and physics .  Deconvolution does not make sense if  any kind of  noise reduction has been done before .. Also the PSF should be derived from the image itself (stars are the best measure of it) , not determined arbitrary because image looks nicer/sharper.  So, BXT at the end of processing is perhaps not a good idea.  Deconvolution is a bit of a paradox, if one wants to do deconvolution accurately , it requires high (statistically) quality data . But when one has high quality data deconvolution is not that much needed anyway. 
So the art is to use it with enough caution 
CS
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CCDnOES 8.34
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Mel Martin:
I use APF-R as a last processing step in an image.


Looks like it is a type of multiscale, maybe MMT or MLT-like....
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Krizan 5.94
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Russell Croman as made it very clear on the Astro Imaging Channel and a discussion with Adam Block that BlurXTerminator should only be applied to linear data. He explained it is not a shatpening tool.  I view it as a final step of the calibration process, and not a post processing tool. It is deconvolution and needs unproceesed linear stars to optain correct meassuerment of the convolution in order to apply deconvolution to the image.  It will work on non-linear data BUT can create artifacts  and false pixels.  You might as well use Topez DeNoise.

Lynn K.
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Steveri 2.11
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I've done this "successfully" as recently as last week , the m31 on my page , one image is pre bXt , the other is that same jpg ran through bXt and i think the result was better.
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Gondola 8.11
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Math is great but that tends to idealize everything. The real world is messy, at the end of the day we're talking about manipulating pixels. There are so many variables in processing, blending and so on that yes, you can follow general rules and it's a good base but sometimes the results of doing something different will surprise you.
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andreatax 9.89
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<— AstroPhotography : Artsy Pictures —>
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jhayes_tucson 26.84
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Wei-Hao Wang:
It may work, or may not.  (Here, "work" means it gives you a sharpening effect without obvious artifacts.  It will never give you a result that's mathematically equivalent to deconvolution.)


Wei-Hao,
I'm going to have to disagree with you here.  Properly implemented, a neural net solution can indeed produce a result "that's mathematically equivalent to a deconvolution."  I believe that Russ has done an outstanding job of being careful to apply the best form of the PSF and he's made it shift variant over the field to handle field aberrations.  There are, in fact, a number of advantages to solving this problem using a NN.  For one thing, the solution is much less influenced by noise.  It is also less likey to introduce ringing artifacts.

The hazard of applying BXT to non-linear data is that it violates the initial conditions assumed for the calculation, which will cause BXT to generate artifacts often referred to in the AI world as "hallucination".   The image below is from my recent talk at NEAIC about galaxy imaging illustrates the problem.  When you use BXT on stretched data, small features are turned into stars, stars are amplified, and many subtle features are suppressed.  This isn't a problem specific to a neural net solution.  You'll also get undesirable artifacts from traditional iterative solutions to the deconvolution problem when you use those algorithms incorrectly as well.

Imagers can do whatever they want but if you want to do a true deconvolution to bring out more "real" detail in an image, BXT should only be applied to linear data...and it should only be applied once.  Using BXT on non-linear data is not a good procedure that would tend to infect the archives here with "imaginary images".

John


image.png
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KGoodwin 4.71
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I've done this "successfully" as recently as last week , the m31 on my page , one image is pre bXt , the other is that same jpg ran through bXt and i think the result was better.

Assuming B is the version with the extra BXT run, it has obvious ringing and "panda eyes" star artifacts, so I would disagree that it is better.
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whwang 15.16
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John Hayes:
Wei-Hao Wang:
It may work, or may not.  (Here, "work" means it gives you a sharpening effect without obvious artifacts.  It will never give you a result that's mathematically equivalent to deconvolution.)


Wei-Hao,
I'm going to have to disagree with you here.  Properly implemented, a neural net solution can indeed produce a result "that's mathematically equivalent to a deconvolution."  I believe that Russ has done an outstanding job of being careful to apply the best form of the PSF and he's made it shift variant over the field to handle field aberrations.  There are, in fact, a number of advantages to solving this problem using a NN.  For one thing, the solution is much less influenced by noise.  It is also less likey to introduce ringing artifacts.

Hi John,

There is probably some misunderstanding.  The sentence you quoted was for running BXT on nonlinear data.  So what I said is not different from what you said about running BXT on nonlinear data.
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