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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Aug 18 2012, 06:00 AM
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Member Group: Members Posts: 345 Joined: 2-May 05 Member No.: 372 |
That's the JPEG compression having an aneurysm.
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Aug 18 2012, 10:45 PM
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Junior Member Group: Members Posts: 36 Joined: 28-May 08 Member No.: 4152 |
That's the JPEG compression having an aneurysm. Something I've been wondering about - are the Mastcam, MARDI and MAHLI JPEG images being recompressed on Earth, or is this JPEG data originally produced on Mars? (I read somewhere on these fine forums that the Navcams use some fancy wavelet compression, but the colour cameras use good old JPEG. I'd love it if some of the raw images were literally that - identical data to that produced on another planet. Being repackaged and recompressed into a more web-friendly form is much more likely, alas...) Pointlessly, I did check an image for EXIF tags, just in case - unsurprisingly there's nothing exciting. CODE Spiral:Desktop afoster$ jhead 0003ML0000124000E1_DXXX.jpg File name : 0003ML0000124000E1_DXXX.jpg File size : 132864 bytes File date : 2012:08:18 15:35:06 Resolution : 1200 x 1200 Comment : NASA/JPL-Caltech/Malin Space Science Systems Transmitting data like the manufacturer's name, camera serial number, focal length and whatever, over and over again, could be deemed an unnecessary use of interplanetary bandwidth? Shame. I imagine useful metadata takes a different route. |
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