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MSL Images & Cameras, technical discussions of images, image processing and cameras
PDP8E
post Aug 28 2012, 12:12 AM
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Back from a little vacation, and catching up on all the threads.
After several attempts to circumvent the JPEG induced color/pattern bleeds in the bayers, I decided to just make a good B&W image. It has several hacks: rank order adaptive noise reduction, reduced resolution to 50%, and multiple stacks.
(and its not that good) huh.gif

Attached Image


... maybe MSSS will take pity on the collective suffering and hacks found here on these threads and authorize a posting of a few PNG raw bayers (just to see if all of the UMSF debayer programs are working properly of course!)



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mcaplinger
post Aug 28 2012, 12:49 AM
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QUOTE (PDP8E @ Aug 27 2012, 05:12 PM) *
... maybe MSSS will take pity on the collective suffering and hacks found here on these threads and authorize a posting of a few PNG raw bayers...

What would be more in keeping with the spirit of the data release policy (IMHO) would be for us to demosaic the data and then JPEG that, but I can't do either one without permission. If raw data acquisition becomes common I'll ask, but I don't think it's worth it for a relative handful of images.


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ElkGroveDan
post Aug 28 2012, 04:06 AM
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Sounds like a great task for a trusted college intern.


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mcaplinger
post Aug 28 2012, 04:44 AM
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QUOTE (ElkGroveDan @ Aug 27 2012, 09:06 PM) *
Sounds like a great task for a trusted college intern.

I have no idea what your point is. It would take me about a minute to process all these images and post them. It's the permission to do so that's lacking.


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JohnVV
post Aug 28 2012, 07:30 AM
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the jpg issue is mostly solved
http://imgbox.com/g/9pzCUh6YaZ
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not "white balanced"
the code used
CODE
gmic  0017MR0050002000C0_DXXX.jpg -bayer2rgb 3,3,3 -pde_flow 5,20 -sharpen 2 -o 0017MR0050002000C0.png


a pde to remove most of the artifacts
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ugordan
post Aug 28 2012, 07:57 AM
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QUOTE (mcaplinger @ Aug 28 2012, 06:44 AM) *
It's the permission to do so that's lacking.

I can understand that posting raws as PNGs would be iffy because we'd be getting the same quality product as you, but why would de-Bayering on the ground and JPEG-ing present an issue?


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ugordan
post Aug 28 2012, 07:59 AM
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QUOTE (JohnVV @ Aug 28 2012, 09:30 AM) *
the jpg issue is mostly solved

John, that looks very smooth, but there's an obvious loss of sharpness in the resulting images.


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RegiStax
post Aug 28 2012, 09:40 AM
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QUOTE (ugordan @ Aug 28 2012, 09:59 AM) *
John, that looks very smooth, but there's an obvious loss of sharpness in the resulting images.

Ive attached a waveletsharpened version of one of the PNG's, its possible to resharpen them without too much of the debayer-artefacts showing up it seems.

cheers
CorB
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jmknapp
post Aug 28 2012, 10:08 AM
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I wonder what the effective bits per pixel of the MASTCAM raw images is. The cameras use the KODAK KAI-2020CM sensor. Is it sampled with a 12-bit ADC like MARDI and NAVCAM? One reference for NAVCAM gives an SNR of >200 for certain conditions. So that would mean effectively 7-8 bits per pixel for that camera anyway?

It was interesting that yesterday Mike Malin referred to stacking images.


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mcaplinger
post Aug 28 2012, 01:48 PM
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QUOTE (jmknapp @ Aug 28 2012, 03:08 AM) *
I wonder what the effective bits per pixel of the MASTCAM raw images is.

The MAHLI paper I've referred to several times before is an excellent source of this kind of information. From section 7.5.1:

"Acquired as 12-bit images, MAHLI data are converted onboard the instrument, without loss
of information, to 8-bit images using a square-root companding look-up table."


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mcaplinger
post Aug 28 2012, 02:03 PM
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QUOTE (ugordan @ Aug 28 2012, 12:57 AM) *
why would de-Bayering on the ground and JPEG-ing present an issue?

I am not authorized to put any data out, in any form. You might want to take a look at http://blogs.agu.org/martianchronicles/201...8/blogging-msl/ -- Ryan discusses in general terms the rules that we operate under. I am constantly evaluating each of my posts to make sure that it is only derived from public information.

If you don't like it, complain to my boss.


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Airbag
post Aug 28 2012, 02:39 PM
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QUOTE (mcaplinger @ Aug 28 2012, 08:48 AM) *
"Acquired as 12-bit images, MAHLI data are converted onboard the instrument, without loss
of information, to 8-bit images using a square-root companding look-up table."


I read that a while back and was puzzled by how one could do any such conversion without a loss of information unless the original data already fit in 8 bits? Any non-trivial processing operation results in a loss of information somewhere (usually with the purpose of increasing apparent information somewhere else).

I understand companding and all that, but that is not a two-way operation without loss of information. The resulting 8 bit data cannot be converted back into the original 12 bit data, surely, as multiple values in the 12 bit sample get mapped to the same 8 bit value?

Just trying to understand what exactly was meant in the MAHLI document.

Airbag
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Floyd
post Aug 28 2012, 03:05 PM
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mcaplinger We all really appreciate the fantastic images released and I think the misundrstanding was that you are bound by image release policy--not being the one doing the releasing. After the appropriate time, the eager ones here will have access to raw data.

Airbag I'm not an expert, but I think it means without loss of spatial resolution. Clearly there is minor loss of brightness precisionin/pixl going from 12 to 8 bit (and back again). However, visually, 8 bit square-root gives full dynamic range and preserves the low-light/dark range preferentially to the saturated white end.


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ugordan
post Aug 28 2012, 03:09 PM
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Airbag, also look up photon shot noise to see why even 12 to 8 bit conversion is "sorta" lossless.


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Airbag
post Aug 28 2012, 04:17 PM
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Ugordan,

But photon shot noise is less of an issue with larger number of photons (i.e. higher CCD signal levels) and that is exactly where a square root compander "does its thing" the most, so I don't see how photon shot noise would be relevant to my original question?

I could understand it if the CCD read noise was a dominant factor, and thus the 12 bits of data are really only "effectively" worth around 8 bits, but that would imply a huge noise contribution!

Airbag
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