[X] My Assistant

[Exploitcorporati...]

Global mosaic:

[Exploitcorporati...]

9-Frame high resolution:

[Exploitcorporati...]

Global with 9-frame inset:

[dilo]

Impressive work!

[RPascal]

Very nice mosaics, congratulations!

When looking at the original images we can sometimes see that the dark crater floors are not as dark as the shadow zones in the craters. Would it be possible to preserve this difference in the mosaic by a slightly weaker contrast, so that details of the dark crater floors are still visible? Or do too many of the original images already have a contrast that is too high?

--René

[Exploitcorporati...]

Very nice mosaics, congratulations!

When looking at the original images we can sometimes see that the dark crater floors are not as dark as the shadow zones in the craters. Would it be possible to preserve this difference in the mosaic by a slightly weaker contrast, so that details of the dark crater floors are still visible? Or do too many of the original images already have a contrast that is too high?

--René

Contrast reduction would probably work. I exclusively used the already dark UV(?) frames for the global view, with all of the high-res pictures adjusted to that, darkening the craters more. As an added handicap, the LCD screen of the scavenged laptop I've been privliged to use was apparently half-frozen in the back of somebody's car in Alaska at some point, leaving the left half of the screen with a pleasant ruby tint and the rest with exaggerated contrast. I've probably overcompensated badly. I'm not even sure what these look like on a normal monitor...by the way, your Huygens work is jaw-dropping, eye-gouging, f@#*ing amazing!!

[Exploitcorporati...]

21-frame (hires inset)

[tedstryk]

21-frame (hires inset)

Darn it...this is tantalizing! The thumbnails look great, but I can't get the images open!

[Exploitcorporati...]

Hires in context(detail):

[Malmer]

started on the same composite but did it in color...

Used IR3 GRN and UV3 as color and CLR as luminance.

HYPERION


It feels like they do some kind of histogram stretching on the cassini "raw" jpgs. (to make the frames easier to wiev for the public I guess)

Makes compositing much more troublesome. (some parts of my composite suffer from clipping in the dark areas due to this stretching)

I guess i should wait until they release the real raws...

/Mattias

[edstrick]

I think they do a simple automatic contrast stretch. If the orignial data is 8-bit, (some of it is 16), and say 5% of the data is below a data number of 43, and 2.5% is above 229 (arbitrary numbers for example purposes), they do a linear contrast stretch mapping 43 to zero and 229 to 255, saturating the bottom 5% of the grayscale black and top 2.5% of the grayscale white.

I don't know the actual percent values.

That's why pics of small moons against black sky saturate them white.

Limb shots of a moon have black sky and that drives the low end stretch.. if the shot is entirely on sunlight moon, the bottom 5% point might be something like 113 and get mapped to black.

[Malmer]

I think they do a simple automatic contrast stretch.  If the orignial data is 8-bit, (some of it is 16), and say 5% of the data is below a data number of 43, and 2.5% is above 229  (arbitrary numbers for example purposes), they do a linear contrast stretch mapping 43 to zero and 229 to 255, saturating the bottom 5% of the grayscale black and top 2.5% of the grayscale white. 

I don't know the actual percent values.

That's why pics of small moons against black sky saturate them white.

Limb shots of a moon have black sky and that drives the low end stretch.. if the shot is entirely on sunlight moon, the bottom 5% point might be something like 113 and get mapped to black.

To bad... they should do the stretching based on the absolute lowest and highest DN. (or preferably not at all...)

But I bet that I am one of the few with this opinion. Most people just watch the pictures on the net... (and the really serious wait until the pds ones becomes available...)

Why complain. At least they let us see the pictures. (esa has a lot to learn)

M

[jmknapp]

Hires in context(detail):

One thing about the Hyperion craters: they often have "gullies" on only one side, the other side being steep. Moreover, the "gully" sides of adjacent craters are often oriented in more or less the same direction. Any explanation for that?

[Malmer]

One thing about the Hyperion craters: they often have "gullies" on only one side, the other side being steep. Moreover, the "gully" sides of adjacent craters are often oriented in more or less the same direction. Any explanation for that?

It has to do with the fact that hyperion has an irregular shape. Most crates are situated on "slopes" and therefore the gravity is not normal to the surface. That causes the crater material to flow more from one side of the crater to the other.

this is also a reason for the large landslides on the sides of the very large crater covering almost the entire hemisphere. (they are very steep compared to the gravitational normal.)



/mattias

Attached thumbnail(s)

 

[jmknapp]

It has to do with the fact that hyperion has an irregular shape. Most crates are situated on "slopes" and therefore the gravity is not normal to the surface. That causes the crater material to flow more from one side of the crater to the other.

this is also a reason for the large landslides on the sides of the very large crater covering almost the entire hemisphere. (they are very steep compared to the gravitational normal.)
/mattias

Interesting... a quick calculation gives a gravitational force on Hyperion less than 1/300th that of Earth, so landslides must be in very slow motion.