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Re: [APML] OT: DSS image processed: Barnard 142/143 Complex ("E"Nebula)
Vicent, the power of this processing software
continues to amaze me. Many of my schmidt shots of
dark nebula are like this, dark brown rather than
black inside, with brigh rims.
Chris
--- Vicent Peris <vicent@cepheusastrophoto.com> wrote:
> Hi Ray,
> I've made two crops of a selected area of the image
> at full size, before and
> after all of the processing:
>
>
http://www.pleiades-astrophoto.com/pixinsight/examples/B142_Crop_Before.jpg
>
http://www.pleiades-astrophoto.com/pixinsight/examples/B142_Crop_After.jpg
>
> As you can see, there is no data loss. In fact,
> there is much more
> perceptible data in the second image! Star colors
> are more differentiated:
> you can easily view the redder stars surrounding the
> dust clouds. On the
> other hand, brightness gradients on the clouds are
> also more defined, due to
> applied noise suppression and large-scale processing
> methods. Therefore, if
> you take into account only the *significant* data of
> the image, you'll see
> that the applied processing has recovered a lot of
> data which was invisible
> in the initial image. Really, do you think there are
> more things to see into
> the original?
>
> I think astronomical image processing has more
> things to do than enhancing
> the data and simulating that the image has not been
> processed at the same
> time. Astronomical image processing must say
> *something* to the spectator,
> leading to some emotional stimulus inside him/her.
> Representing the data
> collected at the telescope by just levels and curves
> adjustments doesn't
> suffice in many occasions, IMO, since our eyes
> *won't notice* all the
> existing data in the image.
>
> Let me explain this with an example.
>
> Here you have two images again. The object is M1,
> from the POSS II. The
> first image is the original RGB combination with
> levels and midtones
> adjustments. The second one is the same data
> processed basically with
> wavelets. All the processing work has been made by
> Juan Conejero:
>
>
http://www.pleiades-astrophoto.com/pixinsight/examples/M1_JC_Original.jpg
>
http://www.pleiades-astrophoto.com/pixinsight/examples/M1_JC_Final.jpg
>
> Download both images and save them on a directory of
> your hard disk. Then,
> look at the images with the Windows' viewer, or some
> similar program
> allowing you to change between both images quickly.
>
> If you take a look at the first image, and then you
> press the PgDown key to
> view the second one, you'll think: "Wow, the second
> image has a lot more
> detail!". But try pressing PgDown again and look for
> a second time the
> "unprocessed" image. Now you'll see more detail on
> the unprocessed image!
> Your eyes are now, after viewing the processed
> image, identifying subtle
> features near the noise level in the original image
> which were not being
> perceived before processing. This demonstrates that
> many features in the
> image must not only be perceptible to the spectator,
> but they must cause a
> *visual impact*. This concept is tremendously
> important! Why do you need to
> apply unsharp mask to an image?? Is this process
> bringing out details not
> present in the original image??
>
> As a pianist, I don't pursue achieving a
> naturalist's or reporter's work. I
> try to achieve a personal interpretation of the
> object that appears on the
> image, but, first of anything, RESPECTING the object
> and its nature.
>
> At this point, processing technics are essential.
> Think on astrophotography
> as a sum of forces. The sum of all of the forces is
> the visual impact. But
> these forces are in a fragile equilibrium because
> they are opposing each
> other: luminance vs. chrominance, small scale
> details vs. large scale ones,
> color balance, static vs. dynamic objects, etc. The
> more perfected a
> processing technique you have, the bigger visual
> impact you can give to the
> image, since the forces will increase, but the
> center of gravity will stay
> stable. Or maybe you want to do an unstable image
> intentionally, perhaps
> enhancing only small scale detail!
>
> But if you raise the visual impact of the image,
> noise will increase too!
> Therefore it is absolutely necessary to make a noise
> reduction to increase
> the visual impact of the image. Without noise
> reduction, you cannot exploit
> all of the expressive resources from the objects.
> This means that after
> processing there can be some areas on the image with
> no noise and also with
> no small scale detail, but this doesn't mean that
> you are losing detail!
> These are two different concepts!
>
> Now see this third M1 image:
>
>
http://www.pleiades-astrophoto.com/pixinsight/examples/M1_JC_LargeScale.jpg
>
> I've processed this one over Juan's result to
> enhance large scale features
> of the object. If you raise the contrast of small
> details, why not to raise
> the contrast of large ones?? I think this is a more
> complete processing,
> since small scale and large scale features in the
> image cause different
> emotions to the spectator. But this would be another
> independent thread! :-)
>
>
> Well, that's all, for now.
>
>
>
> Take care,
>
> Vicent.
>
>
>
>
>
> At 13:12 11/10/2004 +0100, you wrote:
>
> > > Vicent Peris has processed one square degree of
> DSS data for the B 142
> > > region, AKA the "E" nebula.
> > > See it at:
> > >
> > >
>
http://pleiades-astrophoto.com/pixinsight/DSS_Gallery/index.html
> > >
> > > I think Vicent's results are very impressive.
> Hope you like it too.
> >
> >It's impressive, and a great illustration of the
> functionality of the
> >software...but as an aesthetic observation, maybe
> it's been over-smoothed
> >in the wavelets/noise reduction department? It
> reminds me of "space-art",
> >painted with an airbrush...to me it just lacks
> reality, somehow.
> >
> >There's a story, which this image inspires me to
> tell. A few years ago, I
> >assisted a pilot research program of employing
> deconvolution and
> >wavelet-based noise reduction on digital
> mammography x-ray images. We
> >processed the images to "improve" them to our eyes,
> and spent a long time
> >optimising this. But the litmus test was a set of
> clinical trials with
> >radiologists at University College Hospital,
> Galway. The radiologists
> >evaluated the test images under various headings.
> The tests were blind
> >(the "before" and "after" images were presented
> randomly), and our team
> >repeated them several weeks later to check for
> internal consistency
> >(radiologists have excellent memories for image
> details: you have to allow
> >a long time to pass before presenting them with the
> same set of data
> >again, as otherwise they'll just remember their
> previous judgements).
> >
> >The upshot of all this was that what _we_
> considered to be better images
> >(with rather aggressive processing) was not what
> _they_ considered to be
> >better. They were accustomed to seeing certain
> levels
=== message truncated ===
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