[X] My Assistant

[Harry]

"The dark ring around the boundary of the asteroid images is clearly an artifact; I suspect it results largely from the space background outside the asteroid's limb having been set to a uniform black, rather than being real data, with the result that the enhancement goes crazy beyond the edge of real data."

I hope so. However, perhaps it might have been caused from the accumulation of fractional errors. I must check whether there are possible bugs in the software or not...

I attached the image of Metis taken by Galileo probe (left) and its de-convoluted image (right / software: Focus Corrector, focus depth:= 3.6, iterations:=12).

Merry Christmas!

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[Rob Pinnegar]

The dark ring around the boundary of the asteroid images is clearly an artifact; I suspect it results largely from the space background outside the asteroid's limb having been set to a uniform black, rather than being real data, with the result that the enhancement goes crazy beyond the edge of real data.

I don't know about that, Ed. Something I just now noticed is that some of the Vesta images also have a faint (but visible) _bright_ ring just outside the asteroid's "boundaries". See 'em? (Besides that, the space background of the real data would be pretty close to a uniform black, one would think.)

Admittedly, it has been a while since I read up on the mathematics of deconvolution, but my gut feeling is that this could be a sidelobe effect. That's just a guess, though.

[Harry]

The image of Mira taken by HST (left) and its de-convoluted image (right) processed by Focus Corrector (focus depth:=4, iterations:=10)

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[edstrick]

The image of Metis, I can believe those are mostly real details that are bing enhanced. for Mira, my image-processing-instincts say mostly not.

[mike]

Yeah, but it looks cool.

[The Messenger]

The image of Mira taken by HST (left) and its de-convoluted image (right) processed by Focus Corrector (focus depth:=4, iterations:=10)

You're morphing it into a waffle.

[djellison]

Yup - all it's doing is putting an echo of the dark area into the middle, and an echo of the light area outside it. It's certainly not producing any real features.

Doug

[Guest_BruceMoomaw_*]

Waffles In Space! Miss Piggy would be delighted.

[Bob Shaw]

So let's *test* the process with some known targets!

Bob Shaw

[Harry]

You're morphing it into a waffle.

Perhaps Mira is made of waffles. Since the universe is enough vast, there may be a star made of Turkish Delights, too.

[Harry]

"The image of Metis, I can believe those are mostly real details that are bing enhanced. for Mira, my image-processing-instincts say mostly not."

The image of Mira may be just in focus. My software seems not work well when the original image has poor resolutions.

"So let's *test* the process with some known targets!"

Sorry, for I could not find appropriate example so far...

The following images are for Epimetheus taken by Cassini (left) and its de-convoluted image (middle / software: Focus Corrector, focus depth:= 1.8, iterations:= 8). As the reference I attached another image of Epimetheus taken at the position closer to the surface (right).

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[Harry]

The image of Vesta taken by HST (left) and its de-convoluted image (right) processed by Focus Corrector (focus depth:=4, iterations:=9)

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[Harry]

The image of Comet 73P/Schwassmann-Wachmann 3 (fragment "B") taken by HST (left) and its de-convoluted image (right) processed by Focus Corrector (focus depth:=2, iterations:=8)

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[Guest_DonPMitchell_*]

Not to keep nit picking, but "deconvolve" does not mean "sharpen", it is something different from what your program is doing.

In Fourier-transform space, convolution is equivalent to multiplying the image spectrum by a function f. Deconvolution tries to undo this by multiplying the spectrum by 1/f. It's a risky operation, because it can amplify noise. Norbert Wiener derived an optimal filter to bring out the most information given a certain noise level, called a Wiener filter, basically multiplication by 1/(f + c) for a magic value of c. Anyway, it is not just a sharpening kernel.

Photoshop CS2 has a filter called "Smart Sharpen", which I believe is true deconvolution. It seems to do an amazing job once you learn how to fiddle its parameters.

[Guest_DonPMitchell_*]

The following images are for Tempel 1 originally taken by NASA's probe (left) and its de-convoluted image (right). For details of the technique used for that de-convolution, please visit;

http://139.134.5.123/tiddler2/c22508/focus.htm

This got me curious, so I fiddled with this image of Tempel. First, fetch the original TIFF (not JPG) image from NASA. Note that it is 250 x 250 pixels, so undo their pixel-replication by resixing it from 500 to 250 with a "nearest-pixel" option in Photoshop. If you don't do that, all bets are off!

Then I ran it though Smart Sharpen deconvolution, with a radius of 1.5. More than that and the image rings, which indicates you made the radius too big. Here is the original and the deconvolved images, expanded again to 500 with a windowed sinc filter:

[attachment=5837:attachment]

I think the deconconved image is quite a bit cleaner than the sharpened image, although that may have jpeg artifacts amplified, or perhaps it was not downsized to 250 first?