IPB

Welcome Guest ( Log In | Register )

6 Pages V  « < 2 3 4 5 6 >  
Reply to this topicStart new topic
Galileo Imagery, I couldn't find a topic not specific to one moon....
stevesliva
post Mar 12 2010, 04:29 AM
Post #46


Senior Member
****

Group: Members
Posts: 1166
Joined: 14-October 05
From: Seattle
Member No.: 530



QUOTE (volcanopele @ Mar 11 2010, 06:39 PM) *


Paging nirgal...
Go to the top of the page
 
+Quote Post
nprev
post Mar 12 2010, 04:33 AM
Post #47


Senior Member
****

Group: Moderator
Posts: 7040
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Those are just mind-blowing, Jason.

I never knew that there were features like that on Io...(sorry, couldn't resist! tongue.gif)


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
ugordan
post Jul 26 2010, 09:15 PM
Post #48


Senior Member
****

Group: Members
Posts: 3565
Joined: 1-October 05
From: Croatia
Member No.: 523



Shamelessly stealing volcanopele's 10ISIOGLOC03 Io image and running it through CIE XYZ color calculation code based on Galileo's filter wavelengths (R 665, G 559 and V 413 nm):



It's also gamma-corrected (assuming the original composite is straight-up RGB substitution, judging by contrast and terminator line). Io's one of the few moons that doesn't really look bland this way.



--------------------
Go to the top of the page
 
+Quote Post
Decepticon
post Jul 27 2010, 12:29 AM
Post #49


Senior Member
****

Group: Members
Posts: 1157
Joined: 25-November 04
Member No.: 114



Oh wow Gold!
Go to the top of the page
 
+Quote Post
JohnVV
post Jul 27 2010, 05:01 AM
Post #50


Member
***

Group: Members
Posts: 514
Joined: 18-November 08
Member No.: 4489



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
Go to the top of the page
 
+Quote Post
eoincampbell
post Jul 27 2010, 06:04 AM
Post #51


Member
***

Group: Members
Posts: 388
Joined: 28-August 07
From: San Francisco
Member No.: 3511



Really brilliant work here, much appreciated...


--------------------
'She drove until the wheels fell off...'
Go to the top of the page
 
+Quote Post
volcanopele
post Jul 27 2010, 06:22 AM
Post #52


Senior Member
****

Group: Moderator
Posts: 2862
Joined: 11-February 04
From: Tucson, AZ
Member No.: 23



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.


--------------------
&@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io
Go to the top of the page
 
+Quote Post
JohnVV
post Jul 27 2010, 07:10 AM
Post #53


Member
***

Group: Members
Posts: 514
Joined: 18-November 08
Member No.: 4489



color ???? "that is the question " when i did my map i did what i would do in the photo darkroom and balanced for white - then tweeked it for ascetics .I always thought that there was too much green in them
and used the
http://pdsimg.jpl.nasa.gov/data/cassini/ca...0K_0_0_SIMP.IMG
the eastern half
[attachment=22189:tx_1_0.jpg]
Go to the top of the page
 
+Quote Post
volcanopele
post Jul 27 2010, 07:17 AM
Post #54


Senior Member
****

Group: Moderator
Posts: 2862
Joined: 11-February 04
From: Tucson, AZ
Member No.: 23



Wow, yeah, that is WAYYYY too red and dark.

Bjorn has a decent tutorial on Io's color at http://www.mmedia.is/bjj/3dtest/io/index.html .

Another true color approximation that is quite good is at http://photojournal.jpl.nasa.gov/catalog/PIA02308


--------------------
&@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io
Go to the top of the page
 
+Quote Post
ugordan
post Jul 27 2010, 12:53 PM
Post #55


Senior Member
****

Group: Members
Posts: 3565
Joined: 1-October 05
From: Croatia
Member No.: 523



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.


--------------------
Go to the top of the page
 
+Quote Post
tedstryk
post Jul 27 2010, 02:18 PM
Post #56


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4224
Joined: 17-February 04
From: Powell, TN
Member No.: 33



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.


--------------------
Go to the top of the page
 
+Quote Post
ugordan
post Jul 27 2010, 05:33 PM
Post #57


Senior Member
****

Group: Members
Posts: 3565
Joined: 1-October 05
From: Croatia
Member No.: 523



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.


--------------------
Go to the top of the page
 
+Quote Post
tedstryk
post Jul 27 2010, 06:56 PM
Post #58


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4224
Joined: 17-February 04
From: Powell, TN
Member No.: 33



I'm not confusing anything. Not only is the monitor not as bright, the darkest blacks aren't all that dark. As for the two Phoenix images, yes, I am saying that. One is faithful to the brightness of the reflection, one suppresses it in the name of preserving more interesting parts of the image.


--------------------
Go to the top of the page
 
+Quote Post
4th rock from th...
post Jul 28 2010, 01:44 PM
Post #59


Member
***

Group: Members
Posts: 292
Joined: 21-April 05
From: Portugal
Member No.: 347



My non technical argument would be that we use monitors to view every day photographs and video (of ordinary subjects) and the images look correct and "as it should be".
So if we replicate the same processing that our normal digital cameras do and apply it to raw image data, the results should in practice be the same as is if the images were originally taken with that camera.
As for the Phoenix image posted, I'm forced to say that the right version does look like a normal digital photo taken on Earth. Therefore, it's as real as any photo viewed on a PC screen. But this is just my opinion of course.


But more technically speaking, the left Phoenix image is NOT faithful to image reflexion values unless you forced your monitor to display also with a linear response!
If the monitor is sRGB, it will apply gamma to that image, resulting in a non-linear display. So the right version has the correct linear response.


--------------------
_______________________
www.astrosurf.com/nunes
Go to the top of the page
 
+Quote Post
DrShank
post Jul 28 2010, 04:24 PM
Post #60


Member
***

Group: Members
Posts: 161
Joined: 6-March 07
From: texas
Member No.: 1828



QUOTE (JohnVV @ Jul 27 2010, 02:10 AM) *
color ???? "that is the question " when i did my map i did what i would do in the photo darkroom and balanced for white - then tweeked it for ascetics .I always thought that there was too much green in them
and used the
http://pdsimg.jpl.nasa.gov/data/cassini/ca...0K_0_0_SIMP.IMG
the eastern half
[attachment=22189:tx_1_0.jpg]



nice job! what was the color data source / images?



--------------------
Go to the top of the page
 
+Quote Post

6 Pages V  « < 2 3 4 5 6 >
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 2nd October 2014 - 04:30 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.