You left out the partial frames, which you need to fill those gaps.

Very nice! It's too bad nobody has figured out how to remove the shutter smear off the RTG, but it gives us a competitive advantage.

How did you get Mount Sharp that close to the rover? Did it just project that way or did you do something special? If you used hugin what projection did you use?

"Official" thumbnail mosaic:

http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=4837

The full image will probably look the same, only bigger.

I'm glad everyone is enjoying the self-portrait. We worked all day yesterday doing the "official mosaic" of the thumbnails, and I expect we will do the same today on the full-res.

As a courtesy, it'd be nice if people could not broadly release these for a few days. If our mosaic turns out worse, then the better mosaic will win in the end. If you do release anyway, make sure you have the right image credits and be advised that I may be somewhat miffed at you. We've been working on this particular project since before landing and I feel like we are having to rush it to avoid being scooped.


ADMIN NOTE: The UMSF Admin team highly recommends that members use appropriate image credits. See the reference in the MSL FAQs.

"More or less"? To zeroth order sunlight on Mars is just the same color as sunlight on Earth. I'm not convinced we really know what the global sky color and its effect on scene color is, and it is certainly variable as a function of tau and time of day. And people seem unaware that the raw camera images aren't precisely color-balanced for any particular illumination anyway.

If someone wants to say that they white-balance an image in Photoshop because they like the way it looks, that's fine, but they really shouldn't represent that as "what the scene would look like on Earth" without a good deal more work that I see no evidence of anyone having done. (Personally I think a more interesting question is what the scene "really looks like", not what it would look like under some hypothetical light source that it's never going to be under and which is always going to involve some assumptions.)

And that's my last word on the subject, lest I start to sound like a broken record.

It is not enough to discover how things seem to seem.
We must discover how things really seem.
-- Niels Bohr

Maybe I should just shut up, but I'm a purist and can't let it go. When somebody gives me evidence that they know how the camera responds on the basis of ground cal data (which usually involves talking to me) and they show knowledge of the details of color science, then I'll believe they've accurately white-balanced an image. Otherwise they're just approximating or worse.

Unless it explicitly described otherwise, this looks like it was thrown into Photoshop and tweaked until it "looked good", which is a long way from a real analysis IMHO.

Who's "they"? There are people on the project I would trust to do this right, and people I, well, wouldn't.

All I know is what I read on the Internet: http://www.google.com/url?sa=t&rct=j&a...u-A&cad=rja

The as-built Suncams would have had ND5 filters and been basically useless for sky imaging. Optically they were the same as the Navcams and were to be mounted on the HGA. I'm not sure if earlier concepts used fisheye lenses or not.

At any rate, we don't have fisheye zenith-facing cameras so if you want global sky color it has to be done with Mastcam. A zenith to horizon sweep at some azimuthal sampling would be an interesting place to start. Not sure if there is much interest among the science team in this sort of thing and they don't let me push the button.

Maybe the LEDs were being used?

When I said a little bit greenish, I meant that the Neutral 5 square on the Macbeth chart was this color (linearized, averaged, and rescaled to 8 bits):



#657761. Of course, the Macbeth neutral values are only neutral under CIE Illuminant C and these images were taken in bright sunlight (more like Illuminant B ) so there might be some small departure from neutral.

There is no color balancing done in the camera at all. The CCD signal, with the IR cut and Bayer pattern filter throughput and the detector quantum efficiency, is directly converted, run through the square-root encoder, interpolated, compressed, and sent to the ground. No attempt was made to balance this, although because of the way it works out, it is pretty well-balanced for sunlight. For a terrestrial sunlit scene, the raw image is just a little bit greenish, which is more or less what my analysis above says.

As for brightness, perceived brightness is an even slipperier concept than perceived color. Most of these images are auto-exposed to mostly fill the 11-bit histogram prior to companding. What that means relative to how they "should look" is as much a matter of taste as anything else.

In a word, no.

I think people may be confused about the difference between calibration and white balance. Calibration is removing instrument signature. Once it's done, it doesn't need to be done again as long as the instrument stays stable (and there is not much reason for it not to be). White balance is making white things look white in a particular image regardless of whether they would "really look white in reality" (whatever that means). What I was attempting to do was more the former than the latter.

How is this different than any other auto white-balance algorithm? It looks to me like a variant of the standard "gray world" algorithm. http://therefractedlight.blogspot.com/2011...gray-world.html

If you want to make the average color of the scene neutral, it works fine, but that may not be what you really want to do.

That would be "Opacity of the Martian atmosphere measured by the Imager for Mars Pathfinder", Smith, Peter H.; Lemmon, Mark, Journal of Geophysical Research, Volume 104, Issue E4, p. 8975-8986.

Doesn't that imply that shadowed regions would be something like half the brightness of directly-illuminated ones, something which is demonstrably not true for, say, MAHLI images with small amounts of shadowing from the arm? For the one image I looked at, the ratio (linearized) was more like 3.2:1. Of course, this is a tricky geometric radiosity problem and I do admit that the shadows are brighter than I expected.

Mark, do you have a reference for this? I find it very surprising.

It's true that I've ignored the effects of the companding.

Short answer: I would guess so under average dust loading (that's what we assumed to compute typical exposure times, etc), but I am not exactly an expert. The idea of "what it would look like" is so slippery as to start to lose engineering meaning.

http://marswatch.astro.cornell.edu/Bell_etal_SkyColor_06.pdf is a nice try from MER but I'm not convinced it's conclusive or even what question it's trying to answer -- I think the sky color at the horizon.

Why? Do images taken on Earth look blue because the sky is blue? AFAIK, it takes unusual conditions (dust storms or smoke) on Earth to change the color balance of daylight near mid-day. And of course sunlight isn't "white" anyway, so to zeroth order one balances an image so that something that looks white to the eye looks white when the eye looks at the image (more complicated than it sounds.)

This has been analyzed a lot on previous missions, inconclusively IMHO. MSL is the first time we've had broadband filters that approximate the human eye response, so there's some reason to believe that with minor adjustments we can get "natural color". I'm not certain how automatic white-balance algorithms work; see http://en.wikipedia.org/wiki/Color_balance for a start, but ironically, someone has used an MSL image on that page as an example of white balance, and I suspect that image was just tweaked in Photoshop.

I've seen quite a bit of difference in how people are doing color balance of the Mastcam and MAHLI images, both here and in press releases.

I don't know how anyone is doing this specifically. Some results seem too gray or red/pink to me. Without something known to be neutral in the image it's hard to do white balance on any direct basis. Even in fairly dusty conditions, I'm skeptical that there's enough tinting by sky scattering to really affect the color of the scene much, especially near mid-day.

The top of the white pyro box where the Mastcam cal target is mounted seems pretty clean in the sol 3 images. To normalize that to neutral, I multiplied the red channel by 1.06 and the blue channel by 1.13 and the results seemed OK. This is a fairly subtle change, but it gets rid of the green cast in the raws; see example below (raw on the left, processed on the right.)

Yes. See, e.g., http://spacescience.arc.nasa.gov/mars-clim...d_SE_ExAbst.pdf

http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2541.pdf has a table that shows the filter numbering for each Mastcam. If you see six grayscale images of the same scene, they are most likely ordered this way. If there are fewer than six, then you will have to do some guessing for the IR bands.

For the narrowband filters that overlap the Bayer pattern, all needed processing is done in the camera unless the image is commanded raw (which may have happened a few times, I haven't looked.)

The abstract referenced above also has a good discussion of what the filters are useful for.

1 doesn't apply, there have been lots of narrowband filter images taken. Any image that shows up gray in full-res form is probably a narrowband image.

2 is definitely an impediment. For the visible narrowband filters you can figure out the bandpass from the tinting of the thumbnail, for the IR filters you have to guess, from the image order or possibly from the number of hot pixels since the farther into the red, the longer the exposure time in general.

3 and 4 don't apply, lots of the images are normal-sized.

5 and 6 are the reasons I haven't done any false-color stuff.

Are any of the Mastcam images being released in less than 24 hours? (Not counting press release images.)

Yes. The typical rate is [ever heard of ITAR?]

The images are all out there, one can amuse oneself by looking for new hot pixels.