Astro to Astro-art Continuum, 2024 Edition

General discussion about StarTools.
decay
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Re: Astro to Astro-art Continuum, 2024 Edition

Post by decay »

Hi Ivo & Martin, really, that’s far too kind :oops: . Of course, ST is greatly designed to be used without nuts and bolts, bits and bytes and even without too many graphs, diagrams or whatever. But AP really isn’t a simple subject and I think diving a bit deeper can help to get a better understanding of what we are doing. And some bits and bytes and graphs and diagrams might be useful to populate Mike’s Astro-art Continuum. Hopefully ;-)

Martin, I guess getting older also gives the chance to learn and to do new things in life. You decided to go for AP and this is a fantastic great world! And there is absolutely no need to dive too deeply into computers, electronics and maths if you don’t want to. (Which is perfectly fine, of course!)

My youth was in the 80s and I grew up with electronics, soldering and coding the early home computers. The 80s were probably a good decade to learn the basics of all this … :think:

Dietmar.
Mike in Rancho
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Re: Astro to Astro-art Continuum, 2024 Edition

Post by Mike in Rancho »

Due to another discussion about NB palette options, I was doing some googling and came across this article that summarizes steps taken by the pros who process JWST data. https://webbtelescope.org/contents/arti ... mages-made

They also mention it's very similar to what is/was done with Hubble data, so we could probably consider it mostly applicable to visual spectrum images (whether broadband or the usual suspect narrowband filters) as well.

I found it fairly interesting what they deem amenable for healing, repair, touch-up, etc., but that is still a properly accurate representation of the science. And also that the responsible researchers are given veto or suggestion power over the processing, to make sure the image backs up their science and discoveries.

I haven't yet found exactly what processing tools they find permissible, though I get the sense all the usual suspects would be allowed.

And while they do certain things with an aim to showcase particular scientific matters (while still being "engaging"), it seems they are layering together different non-linear stretches of the various filter channels - at least for IR and narrowband. Of course JWST is all IR, so I'm a little more interested in how they might have composted HST SHO. Still trying to dig that up for Hubble, but if the workflow here is the same basic assembly steps, I'm thinking that Hubble (say, Pillars of Creation) may not necessarily have maintained relative NB ratios. :think:
decay
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Re: Astro to Astro-art Continuum, 2024 Edition

Post by decay »

Interesting article, Mike. Thanks for pointing out. The process description starts quite detailed, explaining how the images are aligned and stretched. And most of the other covered topics are described detailed, too. But I wonder if and what is missing. The process of “bringing out the details” (section “Editing for Composition”) is covered rather vaguely. How do they do that? For example, do they use local contrast enhancements, like we discussed before (Contrast, Sharp, HDR modules)? Do they use deconvolution or something like the Super Structure module does?
All these explanations regarding “Removing Artifacts” and the orientation of the diffraction spikes are interesting, but other (missing) topics may be more important?

If they really use FITS Liberator for stretching, like depicted, stretching seems to be rather conservative, using Asinh function (don’t know what ‘Pow’ means. The mathematical “Power” function?). OptiDev is probably more sophisticated.
Mike in Rancho wrote: Sat Feb 24, 2024 9:22 pm I'm thinking that Hubble (say, Pillars of Creation) may not necessarily have maintained relative NB ratios.
I also think that they may not maintain relative NB ratios. I know that Ivo strongly recommends to maintain relative NB ratios and doing not would reduce or even eliminate scientific value and claim. But I wonder if this isn’t just a simple shift in our continuum towards art. And not a quantum leap. Using non-linear global stretching curves compromises the evaluation of brightness levels. Using local contrast enhancements it is not longer possible even to compare brightness levels at different locations of the image. And using different stretching curves for each component – well it additionally compromises relative NB ratios. Probably just one more step towards art?

Best regards, Dietmar.
Mike in Rancho
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Re: Astro to Astro-art Continuum, 2024 Edition

Post by Mike in Rancho »

Hi Dietmar, thanks for adding your perspective. :thumbsup:

I agree with a number of your takes. I would like to see just how they enhance the images, nuts-and-bolts description. And yeah, are they using the same FITS Liberator that I have? Mine is so limited it almost seems worthless, other than reading FITS headers. Though maybe I just don't know how to use it. But, the article does say that after the files are stretched, they take them all into more professional software. They don't say which, just add that Gimp is a nice free program. :think:

I don't think I would say it's a step towards "art," though that all depends on definition and scope. The JWST team does state that things become more subjective. And that's okay! To me the art side is more manipulative, even misrepresentative, alterations, if serving only aesthetic purpose. Like mask subtractions, Forax, and so on. As to the X-tools...nobody knows! ;)

I did come across one page that includes more HST discussion (it takes forever to load but eventually does): https://asd.gsfc.nasa.gov/blueshift/ind ... lse-color/

Also, this page is supposedly the blog of the professional image processors? https://illuminateduniverse.org/

It's a little weird, and I haven't yet read through any of the links/write-ups to see if there are any disclosures about curve stretching, contrast, HDR, denoise, or even sharpening (and if so, what type!?).
decay
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Re: Astro to Astro-art Continuum, 2024 Edition

Post by decay »

Mike in Rancho wrote: Sun Feb 25, 2024 8:13 pm I don't think I would say it's a step towards "art," though that all depends on definition and scope. The JWST team does state that things become more subjective. And that's okay! To me the art side is more manipulative, even misrepresentative, alterations, if serving only aesthetic purpose.
Agreed! I used that word, because of the subject of this thread. I don't like it either. We could use 'enhancing', like it is used in Ivo's table.

BTW: When are we going to continue filling up our table? ;) I'm curious about the other modules, Super Structure, Denoise ...
But of course, I'm not sure if this isn't going to be a 2025 edition ... :mrgreen:

Best regards, Dietmar.
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