Slashdot Mirror
The Real Reason why Spirit Only Sees Red
use_compress writes To produce a color photograph, the rover's panoramic camera takes three black-and-white images of a scene, once with a red filter, once with a green filter and once with a blue filter. Each is then tinted with the color of the filter, and the three are combined into a color image.
In assembling the Spirit photographs, however, the scientists used an image taken with an infrared filter, not the red filter (NYTimes, Free Registration Required). Some blue pigments like the cobalt in the rover color chip also emit this longer-wavelength light, which is not visible to the human eye."
The reason being that the science gets better results using th e IR filter than if the red filter were used... At the moment, despite great public interest, the science is more important... that IS what it's there for....
Simon
Physicists get Hadrons!
'Aha! So that's why they don't see little green men...' - at last, the dream of aliens living on Mars is alive again.
How the Red Planet Came Down With the Pink Blues
They mention slashdot.org by name.
Could this be some sort of revenge?
Can anyone explain why 3 separate B/W images are taken? If it is because of bandwidth... 3 grayscale images weights (more or less) like one color image ... so why B/W and filters?
------- The last Sig. got fired.
It's a good job the pictures aren't coming back with a blue tint, or lynch mobs would be turning up at NASA HQ.
If I seem short sighted, it is because I stand on the shoulders of midgets
I tried showing them to my pet bull and he immediately became bad-tempered and generally unpleasant to be around of. He's much fonder of the Neptune shots from Voyager really...
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
On the panoramic picture: We goofed. It should not have been that red.
The other photographs are taken with the infa-red instead of visible red filter. Iron dominated the visible red spectrum. To allow a better analysis of the compounds found infa-red light is used instead.
<joke>No conspiracy here. Move on.</joke>
the_crowbarHave you read the Moderator Guidelines
They're taking images through blue, green, red and infrared filters. The color shift problem in the publicly released images is because they're blending in the infrared shot instead of the red shot, right? Why don't they just release the RGB images as well as the iRGB? They have all the images after all--why waste press conferences explaining the differences or lack thereof when they could just give us the pictures?
Reminds me of the Gameboy Camera Color Project: http://www.ruleofthirds.com/gameboy/
Some blue pigments like the cobalt in the rover color chip also emit this longer-wavelength light, which is not visible to the human eye."
If it's a *blue* pigment, why does it emit a *longer* (i.e. infrared) wavelength?
The human eye's color vision is a poor scientific instrument. It can be easily fooled.
Mea navis aericumbens anguillis abundat
Quite possibly because it wouldn't survive the conditions on Mars. Or on the way there. Try deep-freezing your digital camera, then put it in a vacuum chamber, then in a really dusty sandbox, and finally subject it to a potentially lethal (for a human) dose of radiation, and see if it still works. Oh, and don't forget simulating the landing; heat it, vibrate it, and toss it on the ground.
Disclaimer: I wasn't there. I don't know exactly how the poor thing was treated. I'm not a member of the PETC (People for the Ethical Treatment of Cameras).
This signature is not in the public domain.
Since nobody else has yet, the registration free partner link: http://www.nytimes.com/2004/02/10/science/space/10 COLO.html?ex=1076994000&en=a6c9abc6b269678b&ei=506 2&partner=SL4SHD0T
Unfortuantly I can't find any references as to the loss{y|less}ness of the compression used
Music is everybody's possession.
It's only publishers who think that people own it.
Fuck Beta
~John Lenno
because that 4 megapixel camera from comp usa is a total piece of crap compared to the 1 megapixel B&W camera on the rover.
I have a old 2 megapixel digital camera that will beat the Best 4-6 megapixel consumer camera you can buy today. because of optics and the design of the CCD. (mine is a TRUE 2 megapixel whereas almost ALL camera's today sold as a 4 megapixel are really a 1.3 megapixel camera as you need 3 pixels for each photographed pixel.. (I.E. one for red,green and blue.)) plus the resolution of each color captured is vastly different, green usually being the best resolution while blue suffer's the most..
Nasa is not about to send the really low grade crap that is available to the cunsumer to another planet. they sent the real deal.
I suggest you actually learn about digital photography and why consumer grade "cameras" are utter junk.
Do not look at laser with remaining good eye.
maybe you should try taking infrared photos?
most of the digital cameras on the market dont have countermeasures to prevent IR exposures, so feel free to experiment with various infrared-transmitting, deep red and light red filters.
from my non-scientific experience, ultraviolet photos of rocks is more interesting than infrared.
they probably wanted better than 5MP resolution - you can get higher res with a high quality scientific b&w camera. if you take 3 still photos through RGB it's functionally identical to a colour camera - i.e. it IS a colour camera - and there would be nothing gained by sending up a "colour" camera that took a single shot and ended up with a poorer quality (but by your definition a real colour picture) result.
The martian crab http://homepage.mac.com/thomasmcgee/ I know, I know, go ahead, mod me off topic. The truth is out there. Would anyone like to start a petition that requests NASA to try to get one more photo of this thing before they drive away?
Art Buchwald has the whole scoop here.
On top of that... 3 colors multiplied by 2 megapixels = the equivalent of 6 'consumer' megapixels.
That was his point. The common 4 megapixel cameras are actually only 1.3 per color.
Regardless, megapixel count is hardly the most important aspect of a digital camera. The lens matters far more, as does the spacing and quality of the pixels. Really, NASA has a very interesting article on the topic.
I've often wondered exactly how rigid the "400-700nm is visible" rule applies. We know that some animals can see infra-red and ultra-violet. But just how well-defined is the wavelength range for human beings? I mean, our bodies are different shapes and sizes, our voices have different pitches, our ears have varying ranges, some of us are allergic to certain substances that others are not ..... but has anyone ever investigated the phenomenon of what wavelengths humans can see? Is it a person-to-person variable, or is it constant for everyone? Can some people see IR, red and green, for instance, instead of red, green and blue? Or green, blue and UV, for that matter ..... and what would it look like?
Je fume. Tu fumes. Nous fûmes!
This problem is not unique to the Mars rovers.
As a hobby and as income, I make borosilicate lampwork beads and sell them on ebay. This requires me to take digital pictures of my beads, which I do with a Nikon Coolpix 885.
Every once in a while I run into a color combination that simply cannot be photographed correctly. One bead set I have looks brown/butterscotch/caramel to the eye, but when photographed using that particular camera, some of the brown features in the bead come out electric red.
Given that we're having so much trouble figuring out what the human eye would see (w.r.t. color), I probably shouldn't even bother to ask, but does anyone know how bright Martian daylight would appear to the naked eye? Insufficiently bright for sunglasses, for example? How (un)comfortable would it be looking at the sun?
I know the human eye is fairly adaptive in this regard, but I'm curious about the qualitative answer to this question. (Quantitative answers expressed in lumens or whatever won't quite do it for me.)
As I understand it, the explanation is simply that the public was given pictures using filters intended for scientific research. This alters the printed colors. At this point NASA should have given more pictures that produce colors closely matching what the human eye sees. With color chips and photoshop(tm), along with a picture taken on earth before the mission, even I could come up with a presentable picture.
I don't know the date of the first use, but Sergei Mikhailovich Prokudin-Gorskii photographed parts of Russia for the Tsar in 1909.
He used a three photo technique where the scene was recorded three times on a glass plate (in a row, not overlaid) with different filters. If you look carefully at the river, there is color distortions from the small waves.
When you take a look at what this old-tech can really do, it's quite astounding.
The Library of Congress has an exhibition of pre-WWI (that's World War I) *color* photos of Russia shot using the exact same process. Since this was a while before any practical color photo printing processes the photographer built a "magic lantern" for "optical color projections."
Props to Bolo Boffin for the link.
Read this and this. These are from the NASA Rover site and they explain it all.
- - - - - - - - - - -
I am a programmer. I am paid to produce syntax not grammar. Deal with it.
This isn't what JPL said. They said they were using a full color, basic digital camera. Damn, where's that link?
Prokudin-Gorskii travelled Russia taking color photos about a hundred years ago, a time when there was no color films. He used to take 3 pictures, one after another, each one with a different filter. He then projected the three together to get a color picture. Similar to Spirit but in a very, very old fashion.
so, i threw this one together the other day, is it anywhere close do you guys reckon?
Spirit-pano-rgb-compose.jpg
Software Freedom Day!.
The Library of Congress has an interesting exhibit up devoted to an early 20th century Russian photographer who used this exact technique. The site includes a very detailed description of how this filter system works, along with dozens of color pictures from the photographer's travels. It's definately worth taking a look at, if not for the description, then for some very cool pictures.
of some turn of the century russian color photos using the same or a similar technique. I like that people thought of doing stuff like this back then. It is amazing to see in color what things looked like back then. I think there are some from early in the 20th Century in New York online somewhere as well.
Well, since they're only using one camera, and switching the filters, that means we can never know the true color of Martians.
This is way off, you've somehow killed the little red, white, and blue flag on the arm.
Pioneer 10 and 11, which both flew past Jupiter in the mid 70's, used only a red and blue-green filter IIRC. They used these two colors to approximate full-color images based on earth-bound images. I don't remember anybody fussing about it back then. A disclaimer of sorts was usually in the more technical articles, but many articles said nothing about it.
Table-ized A.I.
I think people are also forgetting that, on Mars, white light is probably not reaching the surface. The dust in Mars' atmosphere is probably tinting the sunlight a little bit red, which certainly doesn't make getting the "correct" color easy.
But a comparison of the Mars Pathfinder images against the MER images shows that the colors in the MER images are too red. In the MPF images the rocks aren't all the same color.
It's pretty obvious that NASA's been doing a lot of Photoshopping on these images. While some Photoshop'ing is necessary (to merge the 3 grayscale images and to eliminate the seams in the panoramic images), I think they're overdoing it this time. I can't find the link right now, but there's one image in particular where it's blatantly obvious that they've replaced the sky with a single, solid color (you can see jaggies along the horizon in the high-resolution version).
I'm not trying to be all conspiracy theorist or anything. I certainly don't think they're faking the landings, nor do I think the Martian sky is bright blue as some have suggested.
If you use an infrared filter like the L2 filter on Sprit's Pancam, you get data that represents only things which reflect or emit light in that particular region of the spectrum. Anything that emits light ONLY in the red will be absent from the data set. It is possible for something that appears as a fairly monochromatic red to be entirely invisible. How can you use Photoshop to put back something that is invisible? You cannot.
You can adjust an individual colour in the image using a reference image taken with the appropriate filters, and that colour will then appear correct. Other colours, however, will remain distorted.
Worse, you cannot possibly know the emission/reflectivity spectrum of things on Mars, so any image you produce that appears to show the sundial colour chips correctly may distort terribly the Mars components of the image. It is not really very interesting to see a colour corrected photo of the sundial, is it? We could have achieved that without sending the rover all the way to Mars.
Nope, using a relatively narrow-band-pass infrared filter like the L2 simply leaves out information about the red part of the spectrum, and extrapolation only goes so far in recreating that data. Non-linear data - discontinuities within the missing portion of the spectrum - are simply gone, never to be retrieved.
Also, NASA is lying. Perhaps 'lying' is too strong a word, but they are either deceiving us or they are operating under a serious misconception.
"We just made a mistake," said Dr. James F. Bell III, the lead scientist for the camera. "It's really just a mess-up." Well, NASA claims to be releasing the raw data from Spirit on its web site, but the raw data does not contain any image sets for the panoramas taken with the L4, L5, L6 filters. They have almost never used the L4 filter.
So either the "mess up" is that they have forgotten to use the L4 filter from day one (unlikely, since each photograph taken presents another opportunity to switch to the L4) or that they have L4 images but they are not releasing them, in which case they really are not releasing the raw data.
The argument about the L2 being better for science is bogus. There's no way that NASA scientists are doing serious mineral analysis with a pretty, stitched-together wide view panorama. That's just rubbish. they would be looking at detail images, and possibly comparing between detail-level images. The panoramas are strictly for public consumption, and maybe office posters at JPL.
It's probably not a conspiracy, but it is a mystery.
I have it on pretty good authority that it is part of the airbag.
Just wait for more images from MER-B (Opportunity). You're about to see some really cool stuff in the next few days. No Martian crabs or bunnies, I'm afraid, but still some awesome stuff.
- Info (src: Athena)
- Tech Briefing (PDF 52 KB)
- Info (src: Planetary Society)
- Info (src: NASA)
- Info (src: Caves of Mars).
- Filter Specs
(showing approximate color swatches in browser).
--For news, status, updates, scientific info, images, video, and more, check out:
(AXCH) 2004 Mars Exploration Rovers - News, Status, Technical Info, History.
Very good, technical article making point that NASA is not altering colors on Mars (beyond normal minimal adjustments to generate color images, of course).
--
For news, status, updates, scientific info, images, video, and more, check out:
(AXCH) 2004 Mars Exploration Rovers - News, Status, Technical Info, History.
Hm. I'm no meteorologist, but I wasn't seeing any evidence of a dusty atmosphere in any of those rover images. --Details at distance seemed as clear as near objects. There's WAY more crap in Earth's much more robust atmosphere, and we get plenty of white light.
-FL
I hate to be the one to tell you this, but no. No.
First of all, the calibration strip: yeah, the MERs each have something similar as well.
You can't rely solely on them, though. If the light that filters down to the surface is tinted any color other than whitish-blue (like her on Earth), trying to match the calibration device to the one back here on Earth is going to produce the wrong coloration.
Secondly, it's widely known that the Viking lander images showing the Martian sky as blue were colored incorrectly.
Thirdly, the Martian atmosphere is mostly CO2, which doesn't scatter blue light all that much AFAIK. Throw in a surprising amount of reddish-orange dust that's almost always there, and the probability that the Martian atmosphere is usually reddish (or butterscotch) is pretty good. Now, it isn't always reddish, or so I've read. Hubble took a photo of Mars, IIRC, and near the edges the atmosphere looks bluish. This is probably because the light has much more atmosphere to go through at sunrise and sunset than it does during the day, and so what little oxygen is in the Martian atmosphere has a chance to scatter the blue light. There's even a Mars Pathfinder image to back this up right here.
The image doesn't prove that the Martian atmosphere is blue, but it does show that there is a lot of dust in the atmosphere over there, and that under the right conditions it can be a little bit blue in some places.