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Super-resolution challenge, Help requested by the science team
ugordan
post Nov 3 2008, 11:11 PM
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Here's a flicker gif between a single frame and manual stack in Photoshop of the 12 frames, just for fun:



Magnified 2x from original pixel scale. Most likely much better than this can be done. If anything, the many frames allow heavier deconvolution/sharpening to be performed.


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john_s
post Nov 4 2008, 12:14 AM
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Nice! It looks like you did some sharpening- what kind of sharpening?

John.
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ugordan
post Nov 4 2008, 08:40 AM
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I used the Smart Sharpen filter in Photoshop, using the "more accurate" lens blur removal. It produces tighter (and noisier) results than simple unsharp filtering. It's hard to force oneself not to overdo the sharpening, but in this case I do believe it brings out details that aren't resolvable in single frames.


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siravan
post Nov 8 2008, 09:59 PM
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Here is the effect of subpixel shift-and-add on the dataset. The image on the right is the first raw image, enlarged twice and unsharped. To make the one on the left, all the raw images are scaled x8, then the amount of shift for each one compared to the first image (in the x8 setting, i.e. 0.125 pixels resolution in the original dataset) is found and they are co-added taking into account the shift value, and finally the co-added image is rescaled to x2 and processed using the same unsharp filter as the one applied to the image on the right.

The main difference in that unsharping introduced lots of noise to the raw image, whereas the processed image tolerated it much better and some previously unseen features are now detectable.
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john_s
post Nov 10 2008, 08:41 PM
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Thanks to both ugordan and siravan for those images! We're also interested in what can be done with a smaller number of images, 4, for example. Could you try the same thing using just four of the input images?

Thanks,
John.

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Fran Ontanaya
post Nov 13 2008, 09:54 AM
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I had to try. smile.gif



2x
I used 5 images plus one to reduce noise. Mostly was about scaling up without interpolation, aligning the images, do some blending and several steps of gaussian blur and unsharp mask before scaling down --all very empirical. A real pro should be able to do better. tongue.gif


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tedstryk
post Nov 13 2008, 01:07 PM
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Here is my take. I have versions with 4 frames, 6 frames, and 12. First, I deconvoluted the images to combat the broad PSF. I then blew the images up to 5x and sharpened them based on the new artificial point spread the enlargement created. I selectively stacked them, weighting them based on quality (I could probably do a bit better, but I was trying to hurry). After merging the image, I applied a light round of deconvolution based on a 4 pixel PSF and then reduced the images to 1.9x. A slight bit of sharpening was applied at this point.

4 Frames
Attached Image

6 Frames
Attached Image

12 Frames
Attached Image


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tedstryk
post Nov 14 2008, 05:00 AM
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Here is a view of Triton when it was 120 pixels across (shown here at about 2.5x). The inset shows two apparent plumes visible near the bottom of the terminator.

Attached Image


Now that I have worked on the Ganymede stack, might I ask if the image used is the NH frame from the same angle or generated from something else? The reason I ask is that the detail cutoff seems a bit odd compared to the Triton set and other real sets I have worked on. Namely, the technique does much better with high contrast details than low contrast details for obvious reasons. With the Ganymede images, the cutoff seems even. If it is from the lone NH frame, the reason is simple - I am smacking into the resolution limit of the image.


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john_s
post Nov 15 2008, 04:22 PM
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This is a synthetic image using a Galileo photomosaic, but generated with the same geometry as the best New Horizons Ganymede image (for reasons that seemed like a good idea at the time).

Very interesting Triton image- that plume looks fairly convincing! It's a good analog for what we might see on approach to Pluto, where the approach phase angle (15 degrees) is similar.

John.

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Andrei
post Nov 19 2008, 01:23 PM
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I'll take the challenge...I only hope that I'll have some results before NH reaches its target unsure.gif...


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tedstryk
post Nov 20 2008, 01:34 PM
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QUOTE (john_s @ Nov 15 2008, 04:22 PM) *
This is a synthetic image using a Galileo photomosaic, but generated with the same geometry as the best New Horizons Ganymede image (for reasons that seemed like a good idea at the time).

I figured out what the issue is. Most stacks I have worked with include some severely underexposed images. However, the well exposed images were more likely to be smeared because of the longer exposure time. Hence, the high contrast features (the ones visible in even the underexposed but very sharp images) ended up looking better than the fainter features. Given the nature of LORRI (not having color filters), the image sets it produces will likely be more like the Ganymede sample than what I am used to.


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S_Walker
post Oct 16 2009, 04:43 PM
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Sorry I'm late to this test, just joined the sight.

Attached is four images resized 2x, aligned then drizzle combined in MaxIm DL 5.02.
The result is deconvolved using Richardson-Lucy algorithm, PSF of 1.5, 20 iterations.

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S_Walker
post Oct 16 2009, 04:45 PM
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Next is all 12 images resized 2x, aligned and drizzle stacked in MaxIm DL 5.02. THis was deconvolved the same way, but only 10 iterations (more just added noise artifacts).
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S_Walker
post Oct 16 2009, 04:51 PM
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My final version upsamples all 12 images, align then sum combined in Maxim. I then deconvolved the image twice; the first used a PSF of 1.6, 20 iterations, then a PSF of 1.2, 4 iterations.
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