MSL Images & Cameras, technical discussions of images, image processing and cameras |
MSL Images & Cameras, technical discussions of images, image processing and cameras |
Aug 16 2012, 11:05 PM
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
I'm still trying to figure out a number of things about the new images we are trying to work with. Assuming others are likewise trying to learn, I thought I would open this thread to create a place for such discussions.
I'd like to start out with a comment about raw image contrast. There have been several postings in the main threads about whether or not the MSL raw images have been stretched like those from the MER missions. I am certainly no expert on this, but it looks to me as if the MSL images have not been stretched at all. I haven't tried to analyze all of the image types, but the hazcams and navcams have pixel brightness histograms that are very different from their MER counterparts. This attached image compares MER and MSL navcams along with their luminosity histograms. The MSL images clearly are not using the entire, available range of brightness values, whereas the MER raws do. For this reason, the MSL raw images can usually be nicely enhanced by simply stretching the distribution of brightness across the full 256 value range. -------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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Sep 18 2012, 03:41 PM
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Senior Member Group: Members Posts: 1619 Joined: 12-February 06 From: Bergerac - FR Member No.: 678 |
No Fredk. What has been lost, has been lost. If you have black area, or white area, you can't "lower" the contrast to get back some details in these areas
Check this : http://mars.jpl.nasa.gov/msl-raw-images/pr...FHAZ00302M_.JPG Around the Mastcam shadow, you have a white flat area. There were details inside. I'm a little bit angry in my words, but for me, it's a total mistake to stretch picture like this. And come one, the previous ones were no so dark… -------------------- |
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Sep 18 2012, 07:31 PM
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
but for me, it's a total mistake to stretch picture like this. And come one, the previous ones were no so dark… Given that the primary purpose of these images is for people to look at them as they are, without photoshop to stretch them - they have done the right thing. Many of the previous images were too dark. http://mars.jpl.nasa.gov/msl/multimedia/ra...0424M_&s=40 http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00418M_.JPG http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00302M_.JPG http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00417M_.JPG These images would be 'better' for people to look at with the newer stretch. Yes - we get clipping at each end as a result, but the image occupies a larger part of the histogram and, combined with lower compression, is far better for people to actually look at. |
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