Galileo Imagery, I couldn't find a topic not specific to one moon.... Options

[tedstryk]

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.

[JohnVV]

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

[volcanopele]

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.

[ugordan]

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.

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.

[tedstryk]

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.