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, 10:43 PM
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Member Group: Members Posts: 222 Joined: 7-August 12 From: Garberville, CA Member No.: 6500 |
Hopefully what we're seeing has been temporarily utilized for a specific purpose, but if not...
What has been lost, has been lost..... Aaarg so true.... over or under saturation cannot be recovered, period. But it's the disruption of the gray level relationships that's most lamentable to me because that's where much of the textural subtleties and thus potentially valuable scientific comparatives reside. I'm not a trained geologist, but even from an armchair perspective, for a particular rock or patch of soil, slight differences in the average nominal gray levels is often the key to identifying similar or disparate specimens and helps in theorizing their inherent characteristics and relationships. And of course the extreme halo effect overall will make seamless looking mosaics a nightmare. If the reasoning behind this is for the usability of the general public as suggested, perhaps some tweaking is part of the plan and we're seeing the first "extreme" test, after which I would hope that "toning down and tuning in" the level adjustment would be the next move. Hopefully there will be someone in the know here soon enough who can explain the rationale or temporal nature of what we're seeing a bit more. -------------------- "We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time." -T.S. Eliot
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Sep 18 2012, 11:33 PM
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Senior Member Group: Members Posts: 4250 Joined: 17-January 05 Member No.: 152 |
FWIW, my guess is that jpl received masses of emails from the general public saying "these images are too dark". That's why the change. But now that the MSL engineering images look very similar to MER (I'm guessing it's the same algorithm), I doubt very much we'll see further "iterations". It's the masses screaming "too dark" they're reacting too; I'd be surprized if they bent over to tweak the stretching because a few of us complained about clipped whites. Remember that we were also loosing information in the old MSL images, them being effectively around 7 bits instead of 8.
over or under saturation cannot be recovered, period ...until the images appear on PDS! It won't be that long...
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