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Galileo Imagery, I couldn't find a topic not specific to one moon....
tedstryk
post Dec 9 2007, 07:50 PM
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Here is a combination of all of Galileo's global color views of the Galileans. I have left out the large Europa mosaic because much of its color data is pulled from other orbits. I have also left out colorized views. Due to inconsistent filter selection, there some variation between images. I posted the Europa set in another thread, but I figured I would add the views of Ganymede and Callisto.

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JohnVV
post Jul 27 2010, 05:01 AM
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I thought that this one was the correct color and gamma
and have been planing on redoing the color on my map ( i white balanced it )
{ http://celestiamotherlode.net/catalog/show...p?addon_id=1110 }
[attachment=22188:21ISCOLOR_01.jpg]
http://pirlwww.lpl.arizona.edu/~perry/io_images/c21.htm
http://pirlwww.lpl.arizona.edu/~perry/io_i...1ISCOLOR_01.png
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volcanopele
post Jul 27 2010, 06:22 AM
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QUOTE (JohnVV @ Jul 26 2010, 10:01 PM) *
I thought that this one was the correct color and gamma
and have been planing on redoing the color on my map ( i white balanced it )
http://pirlwww.lpl.arizona.edu/~perry/io_images/c21.htm
http://pirlwww.lpl.arizona.edu/~perry/io_i...1ISCOLOR_01.png

Yes, true color...umm... Well gamma, quite frankly, gamma correction has always made images looks too washed out and bright, which maybe more correct, but I don't know, you lose what you gain with our fancy CCD and CMOS detectors.

As far as true color. No it isn't. That uses an Infrared image centered at 756 nm for red, though I tried to not stretch the colors unnecessarily.


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ugordan
post Jul 27 2010, 12:53 PM
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QUOTE (volcanopele @ Jul 27 2010, 08:22 AM) *
gamma correction has always made images looks too washed out and bright, which maybe more correct

It is indeed more correct. The images look more washed out because the objects of interest really are that washed out in reality. If you want to scrutinize the surfaces, higher contrast is great, but if you want more realistic looking images you need to apply gamma correction. I personally don't like the way the terminator appears in higher phase, uncorrected images. It's barely visible and erodes much of the visible disc toward the sunlit terrain.

QUOTE
you lose what you gain with our fancy CCD and CMOS detectors

It's actually more demanding of those fancy CCDs as it exposes any low level noise that would otherwise be drowned out in the darks. Voyager 8 bit is barely workable this way, Galileo is a bit better.

It's hard to illustrate what gamma correction does or why it's important with these distant objects as it's hard to relate to them. I'll give a more down to "Earth" example with a Phoenix image. The left side is uncorrected data, the right side is sRGB correct gamma, same calibrated image, click to enlarge:



You'll notice that apart from vastly higher contrast, there is color shifting present - the surface is redder (not simply more saturated color). It makes talking about "true color" uncorrected images sort of moot.


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tedstryk
post Jul 27 2010, 02:18 PM
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QUOTE
It is indeed more correct. The images look more washed out because the objects of interest really are that washed out in reality.


Not true. On any computer monitor, the dynamic range is much smaller than in real life. Because of this, the "washed out areas" would not appear that way to the eye. These gamma corrected versions are not "more realistic" than other versions. It is simply a matter of picking your poison and deciding which trade-offs you are willing to make.


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ugordan
post Jul 27 2010, 05:33 PM
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QUOTE
On any computer monitor, the dynamic range is much smaller than in real life. Because of this, the "washed out areas" would not appear that way to the eye.


Based on what? The original data is 8 bit. That means a difference of 1 DN translates into 1/256 of total dynamic range covered - determined by exposure, etc. There isn't dynamic fidelity that the eye might otherwise be able to pick out in the original data to begin with.

You are mixing display brightness output and target object contrast. The fact a monitor can not display true luminance of anything other than perhaps Uranus or Neptune systems does not diminish the value of accurate contrast portrayal. Looking at a gamma correct display of a bright target on a monitor is equal to looking at the target through a neutral density filter that dims the object. There is no such filter for the effect straight up RGB substitution gives because it's not a natural effect. It's an artifact of the processing just as incomplete calibration would be.

sRGB gamma was introduced with the sole purpose of mapping more DNs to lower brightness levels because that's where the eye is more sensitive and banding would otherwise be present with 8 bit data. Gamma correction is just a inverse of that so that linear radiometrically calibrated data is presented in the proper way on the screen. It doesn't change the contrast, it brings the actual contrast on screen to par with reality.

You're telling me the above left Phoenix image is just as real as the right one because the computer screen is too dim? All your digital camera images are sRGB gamma correct by default, even though the things you take pictures on Earth are vastly brighter than even Io. So how come they don't appear washed out? Cramming wider dynamic range into a computer screen output is the domain of HDR processing and even it doesn't inherently affect contrast. See example in this site.

The irony is that if the sRGB standard never introduced gamma, i.e. if it left the linear 8 bit approach, we wouldn't be having this discussion. We'd be talking about either natural color and/or contrast-enhanced or saturation-enhanced versions. When an image would be produced and it looked too bland (most of the time), it would be deliberately contrast-enhanced and clearly labeled as such.


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Posts in this topic
- tedstryk   Galileo Imagery   Dec 9 2007, 07:50 PM
- - ElkGroveDan   Galileo imagery? APOD August 30 1996 Great wor...   Dec 9 2007, 08:47 PM
- - nprev   ...wow, Ted! Thank you; that's an incredib...   Dec 9 2007, 09:59 PM
|- - ugordan   QUOTE (nprev @ Dec 9 2007, 10:59 PM) Watc...   Dec 9 2007, 10:22 PM
|- - tedstryk   Actually, I didn't forget....There are so many...   Dec 9 2007, 10:27 PM
|- - tedstryk   This one is actually from Voyager, showing Europa...   Dec 19 2007, 09:03 PM
- - Tom Tamlyn   This seems like the right place to mention that Em...   Dec 19 2007, 10:07 PM
- - nprev   Congrats, Ted; Emily's made you an internation...   Dec 20 2007, 05:22 AM
- - elakdawalla   TTT -- I probably shouldn't refer to my image ...   Dec 20 2007, 03:17 PM
|- - tedstryk   That is a really cool feature. By the way Emily, ...   Dec 20 2007, 04:27 PM
|- - tedstryk   I have re-reworked the closer I32 global view, and...   Apr 14 2009, 01:38 PM
- - PhilCo126   Here's a special image of the Jovian moons: ht...   Apr 23 2009, 08:00 AM
|- - DrShank   nice! but Galileo image compression almost alw...   Apr 23 2009, 07:10 PM
- - Bjorn Jonsson   Having seen what Cassini has done at Saturn I...   Apr 24 2009, 12:25 AM
|- - stevesliva   QUOTE (Bjorn Jonsson @ Apr 23 2009, 08:25...   Apr 24 2009, 02:12 PM
|- - DrShank   QUOTE (stevesliva @ Apr 24 2009, 09:12 AM...   Apr 24 2009, 10:37 PM
|- - ugordan   Yes, Cassini has 12 bit A/D converters and althoug...   Apr 25 2009, 12:40 PM
- - Sunspot   It's a shame its going to be at least 30 odd y...   Apr 24 2009, 10:09 PM
|- - tedstryk   QUOTE (Sunspot @ Apr 24 2009, 10:09 PM) I...   Apr 27 2009, 11:53 PM
|- - tedstryk   Here is another nice view from Galileo, taken duri...   May 1 2009, 06:24 PM
|- - DrShank   QUOTE (tedstryk @ May 1 2009, 01:24 PM) H...   May 2 2009, 04:09 AM
- - Phil Stooke   I expect the other things visible in sunlight were...   Apr 24 2009, 10:15 PM
- - Bjorn Jonsson   This is true and even long exposures might have be...   Apr 25 2009, 01:42 PM
- - Phil Stooke   Cassini at Iapetus was moving very slowly, but Gal...   Apr 25 2009, 04:31 PM
|- - ugordan   True, but Io also receives much more jupitershine ...   Apr 25 2009, 04:39 PM
|- - tedstryk   In these images, compression was not the worst pro...   Apr 25 2009, 08:12 PM
|- - john_s   Actually there are a few low-resolution, global, G...   Apr 27 2009, 10:23 PM
- - machi   Beautiful images! Io is really very photogenic...   Nov 9 2009, 06:06 PM
- - machi   Asteroid Ida in false color.   Dec 1 2009, 11:26 AM
- - djellison   False colour? really? I've stretched the sat...   Dec 1 2009, 11:34 AM
|- - machi   QUOTE (djellison @ Dec 1 2009, 12:34 PM) ...   Dec 1 2009, 11:40 AM
- - Phil Stooke   Since the original mosaic was monochrome, any colo...   Dec 1 2009, 01:28 PM
- - paxdan   I believe machi is using false colour to mean arti...   Dec 1 2009, 01:55 PM
|- - machi   Full inline quote removed - ADMIN Right. This is ...   Dec 1 2009, 02:33 PM
- - djellison   A more appropriate phrase would have been 'col...   Dec 1 2009, 03:20 PM
- - jekbradbury   As Jason Perry pointed out a couple months back ov...   Dec 25 2009, 08:54 PM
|- - tedstryk   Impressive! By the way, I don't think I...   Dec 26 2009, 04:12 AM
|- - tedstryk   I posted a short Europa-related blog entry yesterd...   Dec 28 2009, 06:59 PM
|- - ugordan   Here are two rough color views from Galileo. Valh...   Jan 7 2010, 11:53 AM
- - volcanopele   What a difference rotating an image can make: F...   Jan 21 2010, 10:59 AM
- - machi   Amazing! I'm not geologist, but I have see...   Jan 21 2010, 01:06 PM
|- - DrShank   or a slightly different take, simulating the view ...   Jan 21 2010, 02:53 PM
|- - DrShank   QUOTE (DrShank @ Jan 21 2010, 08:53 AM) a...   Jan 22 2010, 01:10 PM
- - Explorer1   On a related note, look at what made it onto Wikip...   Mar 2 2010, 03:28 AM
- - volcanopele   I had this on my blog a few days ago, but I've...   Mar 11 2010, 10:39 PM
|- - stevesliva   QUOTE (volcanopele @ Mar 11 2010, 06:39 P...   Mar 12 2010, 04:29 AM
- - nprev   Those are just mind-blowing, Jason. I never knew...   Mar 12 2010, 04:33 AM
|- - ugordan   Shamelessly stealing volcanopele's 10ISIOGLOC0...   Jul 26 2010, 09:15 PM
- - Decepticon   Oh wow Gold!   Jul 27 2010, 12:29 AM
- - JohnVV   I thought that this one was the correct color and ...   Jul 27 2010, 05:01 AM
|- - volcanopele   QUOTE (JohnVV @ Jul 26 2010, 10:01 PM) I ...   Jul 27 2010, 06:22 AM
|- - ugordan   QUOTE (volcanopele @ Jul 27 2010, 08:22 A...   Jul 27 2010, 12:53 PM
|- - tedstryk   QUOTE It is indeed more correct. The images look m...   Jul 27 2010, 02:18 PM
|- - ugordan   QUOTE On any computer monitor, the dynamic range i...   Jul 27 2010, 05:33 PM
|- - tedstryk   I'm not confusing anything. Not only is the m...   Jul 27 2010, 06:56 PM
|- - ugordan   QUOTE (tedstryk @ Jul 27 2010, 08:56 PM) ...   Jul 28 2010, 05:51 PM
- - eoincampbell   Really brilliant work here, much appreciated...   Jul 27 2010, 06:04 AM
- - JohnVV   color ???? "that is the question " when ...   Jul 27 2010, 07:10 AM
|- - DrShank   QUOTE (JohnVV @ Jul 27 2010, 02:10 AM) co...   Jul 28 2010, 04:24 PM
- - volcanopele   Wow, yeah, that is WAYYYY too red and dark. Bjorn...   Jul 27 2010, 07:17 AM
- - 4th rock from the sun   My non technical argument would be that we use mon...   Jul 28 2010, 01:44 PM
- - volcanopele   My biggest issue at this point seems to be that th...   Jul 28 2010, 06:03 PM
|- - ugordan   QUOTE (volcanopele @ Jul 28 2010, 08:03 P...   Jul 28 2010, 06:10 PM
- - volcanopele   hmm, that doesn't seem to work, but then again...   Jul 28 2010, 06:27 PM
|- - ugordan   Hmm. I'm stuck with a laptop right now with lo...   Jul 28 2010, 06:38 PM
- - JohnVV   oops i posted the wrong link -- i am going to hav...   Jul 28 2010, 07:59 PM
- - 4th rock from the sun   Regarding image color profiles and the Web: My per...   Jul 28 2010, 08:48 PM
- - JohnVV   well there is AdobeRGB1998.icc HP5000_UVDuraImage...   Jul 28 2010, 09:09 PM
|- - ugordan   Perhaps this digression should be extracted into a...   Jul 28 2010, 09:22 PM
|- - ugordan   An 8-footprint, roughly natural color Galileo mosa...   Aug 30 2010, 06:51 PM
|- - tedstryk   Nice. I have a blog entry about that data set tha...   Aug 31 2010, 04:24 PM
- - machi   Little animation experiment with two Jupiter's...   Apr 1 2011, 07:21 PM
- - Bjorn Jonsson   Wow... When doing these morphed animations, are y...   Apr 2 2011, 02:46 PM
- - machi   Normally I'm using Sqirlz Morph, because of bi...   Apr 2 2011, 03:39 PM
- - machi   Cross-eye 3D view of 11 km high Tohil Montes and R...   Jul 30 2011, 04:24 PM
- - elakdawalla   that is very cool, Machi!!   Jul 30 2011, 06:28 PM
- - algorimancer   That's gotta be the most dramatic view of Euro...   Jul 30 2011, 08:39 PM
|- - volcanopele   QUOTE (algorimancer @ Jul 30 2011, 01:39 ...   Jul 30 2011, 09:43 PM
|- - tedstryk   Yeah, you won't find topography like that on E...   Jul 30 2011, 10:25 PM
|- - algorimancer   QUOTE (tedstryk @ Jul 30 2011, 04:25 PM) ...   Jul 31 2011, 01:54 AM
- - Phil Stooke   Unless it's Europa in Philovision. Phil   Jul 31 2011, 01:02 AM
- - machi   It's my fault, I forgot "Ionian" bef...   Jul 31 2011, 10:43 AM
- - machi   Now, more stereoscopic images (BW and color anagly...   Aug 2 2011, 05:53 PM


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