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Is The Mars Rover Cam Life-Blind?

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posted on Feb, 14 2004 @ 02:38 PM
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Archangel, what if the Martian version of chlorophyl reflects red?




posted on Feb, 14 2004 @ 02:38 PM
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Originally posted by HowardRoark
Again, AA, please explain why you think that algae would even be present on Mars?


It is not impossible for there to be life, and it was one thing that the cam is blind to.

What else can the cam not see?



posted on Feb, 14 2004 @ 02:39 PM
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Originally posted by HowardRoark
Archangel, what if the Martian version of chlorophyl reflects red?


There are gaps between the filters.

The exact spectrum of absorption/transmittance would need to be compared with the filters.



posted on Feb, 14 2004 @ 02:41 PM
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I am quite certain Dr. Phil Plait has seen this, is able to debunk it without showing himself, has motive to, and has not.

[Edited on 14-2-2004 by ArchAngel]



posted on Feb, 14 2004 @ 02:42 PM
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Originally posted by ArchAngel

It is not impossible for there to be life, and it was one thing that the cam is blind to.

What else can the cam not see?


No, it is not impossible for life to exist on Mars. But you are assuming that Martian life would be the same as terestial life. That is a wrong assumption.

Life on Mars would be optimised to survive on Mars.

The Martian environment is radically different from Earth.

Do you think that if we took a sample of algae to Mars that it would survive?



posted on Feb, 14 2004 @ 02:42 PM
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Excuse my ignorance but I assume the rover craft is loaded with instruments outside of visible spectrum too. There should be more than enough ability to find any lifeform within the environment and on the surface and even slightly below it in that region it is in.



posted on Feb, 14 2004 @ 02:43 PM
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Also Arch, those are not what the blue channel and red channel look like, you are blending them with a white background for some reason, giving the inverse of the actual channel. If you are using photoshop, click the little eye on the background layer to hide it.



posted on Feb, 14 2004 @ 02:45 PM
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Keep in mind that the Rovers are geological probes. I believe thatthe failed Beagle was a biological probe. Viking was a biological probe.

And yes, Neo the cameras can "see" into the IR and UV spectrums.



posted on Feb, 14 2004 @ 02:49 PM
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Originally posted by Kano
Also Arch, those are not what the blue channel and red channel look like, you are blending them with a white background for some reason, giving the inverse of the actual channel. If you are using photoshop, click the little eye on the background layer to hide it.


I know. I did it that way to bring up the brightness of the color itself.

The Primary Colors Are Not Red, Blue, and Yellow



posted on Feb, 14 2004 @ 03:00 PM
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Page9:

Kaptain K
Bad PhD
Posts: 2681

One more time. If you had actually read and understood Sarah Mc's post instead of just skimming it for bits you could (mis)use, you would understand that there is no way to get a "true color" image from any set of non-overlapping narrow band filters.



Page 9:

SarahMc
Bad Fellow
Posts: 391

No matter where you place the curves, there are huge gaps between all the filters. They're basicly narrow bandpass filters, and not suited to RGB imaging.

As has been stated over and over again, they will not create a true RGB image. There's no crossover between the filters, even if you use the best case curve based on their bandpass. The L3 filter, at 670nm, is the closest to a typical Red filter in an RGB set, which usually has a peak transmittance around 650nm. The L4 filter at 600nm falls into the typical crossover between green and red on an RGB set, or "orange".

The difference is that an RGB filter set has a much, much broader bandpass - a typical red RGB filter covers from 570 (min transmittance) to around 700 (min transmittance) with peak transmittance at 650nm. Green, from 450 to 650 peaking at 550, and blue from 350 to 550, peaking around 450. That wide crossover between filters is what allows an RGB set to provide a much better rendition. Not only that, the crossovers are usually at the 50% or higher transmission points. Those non-existent crossovers on the pancam are at 0% transmittance. No color data at all for specific wavelengths between filters.

You can not, and will not, ever get an RGB image from narowband filters that effectively eliminate some wavelengths from reaching the detector.


Bad Astro Forum



posted on Feb, 14 2004 @ 03:02 PM
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Correct Neo.


Originally posted by ArchAngel
BOTH determine color.


Yes, perhaps you should understand how.

The ABSORPTION spectra of an object shows what light is not reflected by the object.

The REFLECTANCE spectra of and object shows what light is not absorbed by the object.

To see whether or not the camera can pick up an object you look at the reflectance spectra. Such as the ones given in the pdf file linked to by Barry earlier.

After having a quick look back at the intro to this thread, you also realise that only the ~630nm absorption peak for chlorophyll b doesn't have a filter that lines up almost perfectly?



posted on Feb, 14 2004 @ 03:05 PM
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Originally posted by Kano
Correct Neo.


Originally posted by ArchAngel
BOTH determine color.


Yes, perhaps you should understand how.

The ABSORPTION spectra of an object shows what light is not reflected by the object.

The REFLECTANCE spectra of and object shows what light is not absorbed by the object.

To see whether or not the camera can pick up an object you look at the reflectance spectra. Such as the ones given in the pdf file linked to by Barry earlier.

After having a quick look back at the intro to this thread, you also realise that only the ~630nm absorption peak for chlorophyll b doesn't have a filter that lines up almost perfectly?


You do not have to change all of the frequencies in order to change the color, only some. Take the ABSENCE of red out of chlorophyll and it turns orange.

What does chlorphyll B look like if you use L2 instead of L4?

[Edited on 14-2-2004 by ArchAngel]



posted on Feb, 14 2004 @ 03:15 PM
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Originally posted by ArchAngel
You do not have to change all of the frequencies in order to change the color, only some. Take the ABSENCE of red out of chlorophyll and it turns orange.

Er, you mean if you add red? Yes it would go orange.


What does chlorphyll B look like if you use L2 instead of L4?

It would appear redder, judging from its reflectance spectra. But, to identify something, the composite image would not generally be used. The filters would be used to find the reflectance spectra of the object. (Or more likely the microscopic imager, Mini-TES and other tools would be used). Even though it is a geological mission, the Rovers could be used for superficial biological tasks if the need arises.

As far as "It looks yellow because its blue light. ", thats simply wrong. Blue light looks, blue...



posted on Feb, 14 2004 @ 03:22 PM
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AA, rather than concentrating on chlorophyll, a photosynthesis process you should be considering chemosynthesis as a potential Martian life form.



posted on Feb, 14 2004 @ 03:27 PM
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Er, you mean if you add red? Yes it would go orange.


In an RGB image If you move the transmittance range of the red channel from the absorption range to the relfective range of chlorophyll it will turn from green to orange.

[Edited on 14-2-2004 by ArchAngel]

[Edited on 14-2-2004 by ArchAngel]



posted on Feb, 14 2004 @ 03:34 PM
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Originally posted by ArchAngel

Er, you mean if you add red? Yes it would go orange.


In an RGB image If you move the transmittance range of the red channel from the absorption range to the relfective range of chlorophyll it will turn from green to orange.

[Edited on 14-2-2004 by ArchAngel]

[Edited on 14-2-2004 by ArchAngel]



?????


and your point is?



posted on Feb, 14 2004 @ 03:46 PM
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The cam is color blind.

Depending the the filter combinations used to create the RGB images different forms of algae would have different color.

Green can become orange, like the soil.



posted on Feb, 14 2004 @ 03:53 PM
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Well basicly a CCD sensor is color blind.

Even NASA admits thatthere is some degree of subjectivity in creating the color images.

but, once again, I have to point out that you are basing your entire argument on a questionable assumption, that Chlorophyll as it exists on Earth is likely to also exist on Mars.



posted on Feb, 14 2004 @ 04:01 PM
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but, once again, I have to point out that you are basing your entire argument on a questionable assumption, that Chlorophyll as it exists on Earth is likely to also exist on Mars.


No, I am basing my argument on the fact that the cam is color-blind, it did not need to be, and those who chose the filters should have realized the results.



posted on Feb, 14 2004 @ 04:20 PM
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Originally posted by ArchAngel
It is not impossible for there to be life, and it was one thing that the cam is blind to.

What else can the cam not see?


Continuing to repeat something that is false, does not make it more true. You've been presented with an opportunity to educate yourself on this subject, yet you seem to be going to great pains to AVOID actually understanding what's going on. Why is that?

Your use of the term "blind" is grossly inappropriate in this case, and your citations about the comparisons of "RGB" images to "true color images" is quite simply a misinterpretation of what we are trying to deal with here.

We are dealing with the subset of colors that can be displayed in a quantized fashion. Since we are creating images for display with computers, it is patently obvious that there are colors that your computer can never display.

Recognizing that fact does not mean there is some vast conspiracy, nor does it mean that computers are an inappropriate means for examining color data. There is such a thing as reasonable approximation of photonic data using other means (like computer displays).

Once you recognize that what NASA is trying to build is data for display on COMPUTER SCREENS, then it should become clear that, out of the INFINITE number of color mixes that could strike the human eye, we are really only interested in the 16 million or so points in the COMPUTER RGB DISPLAY SET.

We are looking for mappings that, when displayed via a computer screen, will stimulate human eyes in such a way that the generate meaningful signals for our brains.

To do that, computers need to generate only THREE POINT FREQUENCIES out of the infinite number of naturally-occurring frequencies present in light that hits human eyes in the everyday world.

Stop and think about that for a minute.

Computers can display 16 million different colors using only three distinct frequencies. By your logic, if I created a set of filters that blocked out everything but a narrow bracket around those three frequencies, and took Pancam photos of a laptop screen, I still couldn't see "color", because look at all of the frequencies I couldn't see, and no overlapping bands to boot!

We are looking at a reasonable compromise between what a human eye can see, and what a computer screen can display. Of the two, the computer screen is the one that is far more limited in capabilities.

The functionality of the Pancam was not built around trying to mimic human eyes. Instead, it was built around trying to gather light REFLECTANCE data from objects using a variety of bands. Each of those bands provides information of different kinds, and some of those bands can be combined to provide RGB signals FOR COMPUTER SCREENS which will carry enough data to be "close enough" to what a human would see... and that makes them quite useful.

There are an infinite number of points in the color-mix space that can be seen by human eyes. Computers can display only a tiny fraction of that (16 million is a hell of a lot less than infinity...) Yet I don't hear anyone crying about the fact that computers are somehow grossly inappropriate tools for trying to do analysis of "color" images in order to extract meaning from them.

If you take the opportunity to educate yourself on hyperspectral imaging, you'll see that it is not that uncommon to have a variety of fairly narrow-bandpass filter images for CCD systems being used to pull LOTS of good data together, despite the fact that they don't necessarily measure every point in color space, and in almost every case fail to overlap their bands.

Chlorophyll is a good example. I've already explained in quite some step-by-step detail how a composite using the L3-L5-L6 channels for (computer) RGB would show a highly convincing green signal in a Pancam shot of plant life.

You act as if my explanation was never even offered.

The term "RGB" means different things in different disciplines. In the context of this conversation, you'll need to remember that the ONLY context which is appropriate for the purposes of this discussion is computer screen RGB, not human-vision RGB.

As Kano outlined, human vision has three overlapping response curves. The quote that you keep trotting out in various places refers to human vision response curves, not color display using computer monitors.

Computer monitors display color solely via the additive application of three different, distinct frequencies, at varying degrees of intensity. That's it. Your computer monitor has no "overlapping curves" either.

Which conspiracy caused that?

You could take a multispectral shot of a decent LCD display showing a rich color scene, but when you decompose it, you'll see three incredibly narrow spikes.

Since the Pancam is trying to generate data that a computer screen will use to create images, the question is definitely NOT "which frequencies can't the Pancam see", because at least one filter can see EVERY frequency in the human range at some level of brightness... as I already pointed out to you, but you apparently keep ignoring.

The more appropriate question is whether the Pancam filters can be used in appropriate combinations to create COMPUTER IMAGES that are reasonably useful.

And they most certainly can. Will they be identical to what your eyes would see? Of course not... but your computer couldn't display that anyway. So instead, we are left with trying to come up with reasonable points in the data space that "come close enough".

Of course, the other advantage is that this gives the scientists even more useful combinations than some theoretical "true color" method, since they can combine a wide variety of combinations beyond just the typical 3-axis data used by computer monitors.

We can look at deductive comparisons of the different frequency outputs, and determine useful things about given sets of pixels that go far beyond what a human eye could ever determine. It's a nice side effect that we can produce reasonable facsimiles of human-friendly color schemes along the way.

Understanding how to use the data means knowing when other similar-sounding concepts are simply INAPPROPRIATE, and this is typically when they are wrongly applied to a different discipline.

As you said elsewhere: "I learned about this before digital, and am a novice with Photshop."

Maybe that should act as an indicator to you that you might not understand everything that's involved here... and that your lack of understanding should not serve as support for (or constitute evidence of) some conspiracy on the part of the Pancam designers.

Until you understand why chlorophyll looks green to human eyes, and how a computer goes about representing that, and how the Pancam can produce a computer image that indicates that... you simply won't understand whether the tool is reasonable or not.

An infinite number of mismatched-context quotes will not change that in the slightest.

Learning, however, can change it. If you have questions (instead of off-base proclamations) that will help further your understanding, please feel free to ask them.

Without that, I think you're simply basing your position on a combination of ignorance and confusion.



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