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Ingenuity- Mars 2020 Helicopter, Deployment & Operations
Bill Harris
post Sep 23 2021, 02:36 AM
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Stereo Photo Maker is a good tool to work with anaglyphs. I've always been able to view stereo pairs with my bare eyes, so I've never been that keen on anaglyphs. Well, I've developed a cataract in one eye and can't do stereos til I get it fixed.

--Bill


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tau
post Sep 23 2021, 08:16 AM
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Thanks to nprev for interrupting the unpleasant argumentation in the other thread.
In the meantime, I've prepared a replay on a post by mcaplinger that may be of general interest.

QUOTE (mcaplinger @ Sep 22 2021, 07:42 PM) *
The color balance of this COTS camera has been quite unpredictable if you go back and look at all of the images. Having said that, are these rocks "bluish" by some metric, sure, wouldn't surprise me. . . .

Here is an overview of all helicopter raw color photos so far.
The white balance was sometimes changed for unknown reasons. I checked all raw images from sol 193 (here is a link to one of them).
Apparently, the images on sol 193 were processed in-camera with an automatic white balance that completely removed any color cast.
This can be verified by averaging the values of R, G, and B in each image. They are identical R=G=B within a rounding error of 1.
This means that the average of all colors in an image is a neutral gray. Because of the predominant orange tone in the Martian landscape,
this auto white balance results in some bluish features (sky, some rocks) in the raw images.

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Bill Harris
post Sep 23 2021, 05:43 PM
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Tau, my suspicion (and I have no proof) is that a color balance change was applied as the images were archived. Unless a bit gets flipped in the on-camera setup, that color balance setting is not likely to change. I would even doubt that there is a way to change it on the aircraft. Tweaking an image "in post" is the likely explanation.
Remember, this is a simple, but high quality, color camera placed on a technology demonstration aircraft.

--Bill


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mcaplinger
post Sep 23 2021, 06:55 PM
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QUOTE (Bill Harris @ Sep 23 2021, 09:43 AM) *
Tau, my suspicion (and I have no proof) is that a color balance change was applied as the images were archived.

I don't think this is the case, I think that the white balance behavior changes unpredictably as a function of what's in the scene and possibly due to some adaptive algorithm inside the camera.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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fredk
post Sep 23 2021, 09:21 PM
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QUOTE (mcaplinger @ Sep 23 2021, 07:55 PM) *
I don't think this is the case

That sounds right. If you compare these two sol 64 frames from the main "raw" image server they have very different colour balance, even though they share some of the same ground features:
https://mars.nasa.gov/mars2020-raw-images/p...3_000085J02.png
https://mars.nasa.gov/mars2020-raw-images/p...0_000085J02.png
The corresponding RAD calibrated images on the PDS look more similar to each other, but still quite different:
https://pds-imaging.jpl.nasa.gov/data/mars2...3_000085J04.png
https://pds-imaging.jpl.nasa.gov/data/mars2...0_000085J04.png
So the different colour balance has only been partially corrected in the calibration. That suggests the different balances are in the original (downlinked) images, rather than in post-processing.
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