[X] My Assistant

[remcook]

Iapetus: amazingly black-and-white

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7097

Rhea:

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7106

Tethys:

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7107

[remcook]

Mimas! Huh?! Cut in half?! why the sharp terminator (and in the first one there is also light coming from the side, but that could be from saturn)? in the scond one you see the large crater I think.

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7030

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7108

Dione:

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7033

[Guest_Sunspot_*]

How did they all end up overexposed lol

[djellison]

This is the problem - they probabyl are not overexposed, but the stretching done - probably automatically - before they get dumped onto the web basically RUINS the pictures! GRGRGGRRGRG

Doug

[Guest_Sunspot_*]

Reading through the RAW image FAQ it says the images haven't been processed in any way. There is also a section on why some images are over exposed.



Why is the image overexposed?

Cassini's cameras have 63 different exposure settings, from 5 milliseconds to 20 minutes. Scientists planning an observation must choose the exposure for each image taken. That can be tough if you're taking a picture of something you've never seen before. Thus, incomplete information on how bright something can be can lead to an underexposed or overexposed image.

Images can be overexposed on purpose too. If the scientist is looking for something dim next to something bright, the bright thing may be overexposed. Finally, Optical Navigation personnel use images to see where Cassini is relative to Saturn and its moons. Often they overexpose images because they need to see where these moons are in relation to the stars in the background sky.



Why does the image look sideways or upside down?

When a photographer tilts his or her camera to best fit the scene, the resulting images may appear sideways or at an angle. The same is true for Cassini - the images reflect the orientation of the photographer, in this case the spacecraft. The images on this web page have not been processed in any way, so there is no guarantee that the images will consistently show North at the top of the frame. [B]

[Guest_Sunspot_*]

There's a lovely new wide angle shot of Saturn and its rings:

http://saturn.jpl.nasa.gov/multimedia/imag...feiImageID=7032

[djellison]

I think our man on the inside can confirm there is more detail in those images than we get to see in the 'raw' jpgs

Doug

[volcanopele]

They look fine to me I think I can smuggle you a few unprocessed but non-saturated versions of those images.

[djellison]

They look fine to me I think I can smuggle you a few unprocessed but non-saturated versions of those images.

It's the difference between a botched 8bit JPG, and a lovely 12bit PROPER raw image I guess

Doug

[Guest_Sunspot_*]

I did notice the majority of the distant pictures of Phoebe appear over-exposed. The RAW image FAQ states they haven't been processed in any way, so what exactly happens to these RAW images before they're placed on the web?

[djellison]

I did notice the majority of the distant pictures of Phoebe appear over-exposed. The RAW image FAQ states they haven't been processed in any way, so what exactly happens to these RAW images before they're placed on the web?

They get..umm. processed They have to be - most of the images taken are 12bit images - and a JPG can only be 8bit - so there HAS to be processing by default. That processing is done automatically I assume - and the algorythm for it is a bit stupid - it just takes the brightest thing in the scene and makes that white, and the darkest thing in the scene and makes that black - and interpolates ( badly ) inbetween.

If it was done more intelligently, we would see moon detail - I am sure. You dont build a multi-billion $ spacecraft, fly it billions of miles, and then get your exposures THAT wrong

Doug

[volcanopele]

Here is Mimas

Attached image(s)

 

[volcanopele]

Here is Enceladus

Attached image(s)

 

[volcanopele]

Here is Tethys. Note the N-S assymmetry.

Attached image(s)

 

[volcanopele]

Here is Dione.

Attached image(s)