MSL Images & Cameras, technical discussions of images, image processing and cameras |
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MSL Images & Cameras, technical discussions of images, image processing and cameras |
 Sep 23 2012, 09:08 PM
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#136
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Founder  Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1  |
QUOTE (vikingmars @ Sep 23 2012, 03:50 AM)  It's a real pity... Whats a pity? The middle of the ring magnet is rather clean. That's the point of them. |
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Sep 23 2012, 09:31 PM
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#137
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Junior Member Group: Members Posts: 31 Joined: 10-August 12 Member No.: 6526 |
QUOTE (djellison @ Sep 23 2012, 02:08 PM) Whats a pity? The middle of the ring magnet is rather clean. That's the point of them. I thought this post and referenced link indicated that the magnets were ineffective due to being placed at an incorrect depth below the surface of the color swatches: http://www.unmannedspaceflight.com/index.p...mp;#entry191828 If true, this would seem to be a "pity". Edit:  Mark |
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Sep 23 2012, 10:44 PM
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#138
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
Let's see if Mars behaves the same as that wind tunnel test.I'd be surprised if it does- Mars rarely plays by the rules.
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Sep 24 2012, 10:19 AM
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#139
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 Senior Member Group: Members Posts: 1084 Joined: 19-February 05 From: Close to Meudon Observatory in France Member No.: 172 |
QUOTE (markril @ Sep 23 2012, 11:31 PM) If true, this would seem to be a "pity". Edit: MarkAgree. Here are my color calibration target sampling tests results(*) done last week with Sol 13 vs. Sol 44 samples (taken in the middle of the ring magnets). There are still hints of colors on Sol 44 on the targets (especially for the blue target), but globally colors are much less saturated (especially on the red and yellowish-brown/ochre targets) and with results remarkably similar for both MastCams... (confirming, by the way, that both are well calibrated... of course !)
(*) Tests done with images I produced from raw imaging data by equalizing the raw images on grey values. The images shown hereabove are the fully calibrated final products |
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Sep 24 2012, 02:35 PM
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#140
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 Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
The lighting's very different between those sol 13 and 44 shots - that may change the colours, even though the colour targets have a pretty flat/matte finish. Also exposures may be different - or have you tried to compensate?
Have you looked for pairs with more similar lighting? |
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Sep 24 2012, 03:09 PM
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#141
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 Member Group: Members Posts: 150 Joined: 3-June 08 From: McLean, VA Member No.: 4177 |
QUOTE (vikingmars @ Sep 24 2012, 05:19 AM) ...Here are my color calibration target sampling tests done last week with Sol 13 vs. Sol 44 samples (taken in the middle of the ring magnets). Very interesting. I agree with fredk, though. I would think the highly specular reflection off the target from the late afternoon sun on SOL 44 would goof up the comparison significantly - there looks to be some specularity from the matte colors as well. I'm really interested in the effect of global illumination from the dust in the atmosphere at different times of the day. I've been using the Kapton tape all around Curiosity to try to get a notion of color under that illumination, in shadow and sunlit, and assume that it would be more amberish than under blue sky here. When I saturate the colors for that Kapton, I get a much more colorful landscape! Relentlessly orangy/browny
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Sep 24 2012, 03:46 PM
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#142
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Senior Member Group: Members Posts: 1084 Joined: 19-February 05 From: Close to Meudon Observatory in France Member No.: 172 |
QUOTE (fredk @ Sep 24 2012, 04:35 PM) Thanks for your interesting questions. Here are some answers : Q/ : The lighting's very different between those sol 13 and 44 shots - that may change the colours, even though the colour targets have a pretty flat/matte finish. Also exposures may be different - or have you tried to compensate ? A/ : Yes, compensation with brightess only, NOT with contrast and saturation ; Q/ : Have you looked for pairs with more similar lighting ? A/ : I found none yet, but anyway my pics are processed to be equalized on the grey MSL cover on which the sundial is positioned and this gives to all pics the same basis for comparing hues, as explained in previous posts : http://www.unmannedspaceflight.com/index.p...st&p=191206 http://www.unmannedspaceflight.com/index.p...st&p=191226 This technique has always worked well for comparing hues and dates from the "old" Viking times. The best evidence for the effectiveness of this process comes from the similar results that are obtained for sampling tests for both cameras (MastCam-34 and MastCam-100), with images taken with different contrast on Sol 44... (=> PS : To answer the note herebelow : I agree with the statement regarding the raw data. But, I should have insisted more on the fact that the images shown hereabove in my sampling tests are the fully calibrated ones I produced from this raw data by equalizing the raw images on grey values as explained before. In such a case, "JPG's on a rapid release raw website" works very well as a source of images and, besides, this is where lies the beautifulness of this technique I learnt at JPL) |
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Sep 24 2012, 04:52 PM
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#143
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
Note - you're not using calibrated data - you're using JPG's on a rapid release raw website. You're not comparing apples to apples at this point.
Calibration targets get dirty. It happened on Viking, MPF, MER, PHX...and it's happening on MSL. |
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Sep 24 2012, 05:31 PM
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#144
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 Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
The date on that magnet study was June 2011, which brings up a question of why wasn't the situation fixed--was there not enough time, or perhaps did not everyone believe the wind tunnel simulation? The answer is in the conclusion of the linked thesis:
QUOTE The MSL magnet had almost no lee-side dust-poor area and the center area of the magnet was dustier than the reference area. This was a surprise as computer simulations predicted that the center would be kept clean. It is believed that some of the simplifications incorporated into the simulation were probably responsible. However, this experimental result indicates that in less than a month a large part of the blue, green, yellow and red areas just above the embedded magnets on the MSL calibration targets will be almost completely obscured by dust. Removal of the magnets hasn’t been possible at this late stage, so the surface imager calibration team will just have make do with what remains of the areas of color chips and with the different gray color areas, and write the calibration programs primarily using only them. This is not as bad as it sounds luckily, as the gray colors are the most crucial for calibration. There is also still the hope that the very uncertain estimate of the depth of the magnets will be in the very shallow end or some other differences between the experiment and real life will end up in favor of a [sweep] effect stronger than predicted and hence of better calibration measurements.
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Sep 24 2012, 05:59 PM
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#145
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Senior Member Group: Members Posts: 2511 Joined: 13-September 05 Member No.: 497 |
QUOTE (jmknapp @ Sep 24 2012, 10:31 AM) why wasn't the situation fixed... In my opinion, the instruments were well-calibrated on the ground and the calibration target is not really needed. Given the number of images being taken of the cal target, this seems to be a minority opinion.  With all due respect to the people supplying the magnets, I'm not sure they understood the needs of imaging or the dynamics of the landing dust environment. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Sep 24 2012, 06:11 PM
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#146
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
Note that the thesis concludes that " in less than a month a large part of the blue, green, yellow and red areas just above the embedded magnets on the MSL calibration targets will be almost completely obscured by dust" - 48 sols in and I don't think we could say that they're 'almost completely obscured' so we already have reason to question its conclusions.
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Sep 24 2012, 10:32 PM
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#147
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Senior Member Group: Members Posts: 1084 Joined: 19-February 05 From: Close to Meudon Observatory in France Member No.: 172 |
QUOTE (djellison @ Sep 24 2012, 08:11 PM) ...48 sols in and I don't think we could say that they're 'almost completely obscured' Agree with you : not completely obscured. A few colors can be still retrieved now on the MSL targets, more than a month after its landing, on the blue and green channels, which is not too bad after all. And, as said above, "gray colors are the most crucial for calibration"... Let's wait a few more weeks then... (=> PS : By the way, this interesting thesis reminds me the difficult calibration of MPF color images in 1997 using its 5 targets. Herebelow is a Sol 2 except from MPF's "Insurance Pan"... The targets were not yet dusty. Enjoy !)
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Sep 24 2012, 11:53 PM
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#148
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Junior Member Group: Members Posts: 32 Joined: 17-April 05 Member No.: 235 |
QUOTE (djellison @ Sep 24 2012, 02:11 PM) Note that the thesis concludes that " in less than a month a large part of the blue, green, yellow and red areas just above the embedded magnets on the MSL calibration targets will be almost completely obscured by dust" - 48 sols in and I don't think we could say that they're 'almost completely obscured' so we already have reason to question its conclusions. 1997? |
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Sep 26 2012, 06:50 AM
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#149
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 Member Group: Members Posts: 161 Joined: 12-August 12 From: Hillsborough, NJ Member No.: 6546 |
There appears to be dust on the right MastCam according to the subframes from sol 48. Do the lenses get brushed at all?
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Sep 26 2012, 07:31 AM
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#150
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 Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Do you mean the little fleck on the middle top of the recent daylight Phobos pics? It might be too far for the DRT to reach...
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