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Explaining the Mars Photo Colorization
TaddyPorter writes "I've seen stories going around the 'net in regards to NASA editing photos of mars. Mainly, the sundial used for calibration showed different colors than the dial on mars. While a wide range of explanations were taking shape, the Pancam Payload Element Lead for the mission, Jim Bell of Cornell University, was kind of enough to explain the color differences."
If blue appears pink on Mars, what is the real color of the little green guys?
They could have used a Foveon Sensor if they didn't want Bayer interpolation.
I have a Sonly Clie' PDA with a digicam built in, and it can be used to demonstrate how digicams "see" color differently, especially in the near-infrared range.
If you go into the camera application and aim the Clie' at an infrared remote control (like a TV or stereo remote), and hit one of the buttons on the remote, the PDA camera will pick up the infrared and actually display it visibly!
...doesn't NASA throw the public a bone? This color correction controversy pops up everytime a probe successfully lands on Mars and sends pictures back. One would think that they would have a standard RGB style camera for publicity shots. Chances are they can only afford to put on cameras practical for the mission, but I still believe a better solution could be provided. It probably just wasn't important to them... ;) Perhaps next time a camera could be included that features lens that provide scentific data and that can double as a publicist for NASA - spitting out RGB standard images that require no color correction.
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Mirror here...
TOP STORY: NASA Is Not Altering Mars Colors.
Posted by: Kano
On: Sun January, 18 2004 @ 03:34 GMT
This article is a brief summarised explanation of how the PanCam on the Mars Spirit Rover operates, in relation to the strange appearance of the calibration sundial in some pictures. The question was first raised by ATS member AArchAngel, and has been discussed at length in this AboveTopSecret forum thread and ATSNN story:
thread
Mars Spirit Rover Picture analysis.
In this thread I will attempt to summarise my posts to the larger thread.
What are you talking about?
Ok, the initial alarm was raised after it was noticed that the color-calibration sundial mounted on the rover, looked quite markedly different in the Mars-Panorama shots compared to its regular appearance.
Immediately wide-ranging theories began to pop up. At this stage I knew very little of the particulars of the PanCam so I decided to go and see what the Horses mouth had to say. I sent out a swag of emails to the NASA marsrover team, the Athena Instrument team at Cornell University, and the long shot, an email to Assoc. Professor James Bell. Who is the Pancam Payload Element Lead for the mission.
Now, getting no response from the Athena team, and an automated response from the NASA team. I was amazed and delighted to see that Dr. Bell had indeed taken the time out of his busy schedule to help explain this quirk in the panorama pictures. His email response is below:
quote:Thanks for writing. The answer is that the color chips on the sundial have different colors in the near-infrared range of Pancam filters. For example, the blue chip is dark near 600 nm, where humans see red light, but is especially bright at 750 nm, which is used as "red" for many Pancam images. So it appears pink in RGB composites. We chose the pigments for the chips on purpose this way, so they could provide different patterns of brightnesses regardless of which filters we used. The details of the colors of the pigments are published in a paper I wrote in the December issue of the Journal of Geophysical Research (Planets), in case you want more details...
All of us tired folks on the team are really happy that so many people around the world are following the mission and sending their support and encouragement...
Thanks,
Jim Bell
Cornell U.
Now, as far as the pink tab where the blue one should be, that email is infact the complete answer. But its not easily understandable to the layman. Below I will attempt to explain why this occurs.
Click here to read comments or post your own.
Displaying the first 12 replies to this news story...
Posted by: Kano
On: Sun January, 18 2004 @ 03:35 GMT
Digital Cameras
Firstly, we need to understand how the PanCam, and indeed digital photography in general works.
Luckily for us we have our good friends at http://www.howstuffworks.com to turn to.
How Digital Cameras Work
It would be worthwhile to read the entire article on howstuffworks, for a fuller understanding of the processes at work. But because I know you are all busy (lazy?) I will summarise.
Basically, the heart of a digital camera is the charge coupled device or CCD. This CCD converts light hitting it into electrical impulses, the brighter the light, the stronger the impulse. Now, CCD's are color-blind. All they do is signal how bright the light hitting them is. All well and good for black and white photography. But for color we need to do more. To get a color-picture. We need to record images via the CCD using a series of 3 filters. A Red filter, a Green filter, and a Blue filter. These are then recombined afterwards to give a color-representation of the picture. (Note, cheaper options like the Bayer filter pattern are often used in commercial digital cameras, but they use interpolation and are subsequently less accurate than 3-filter methods.
Never True Color
Quite a big deal has been made o
Make even shorter URLs - 8LN.org
This just in: most of the images from Hubble are also colorized, apparently because some people took offense to not being able to see in the infrared. Additionally there appears to be a hint of the same fiasco at many radio telescopes.
If you look at one of the earlier panoramas (e.g., in grey or the partial ones in colour), it is pretty obvious why -- with the sun present, the range of brightness in the image is extreme, and it is difficult to get reasonable contrast from the ground unless you ignore the sky and over-stretch the contrast until the sky is almost white. It is worse when trying to make an image from a series of differently-exposed tiles. Because the sky is not the most interesting part of the image, and it just takes up extra space in the file, I think they just selected it, cropped it out, and set it to an even shade so it would compress well and not look messy with lots of seams between tiles.
I'm sure they will make some more full-res colour panoramas that include the sky eventually.
Well, if you zoom in even further, you'll find that everything is made up of tiny squares of different colors. The odd thing about it is that they are COMPLETELY square, as if the moon was built from Lego bricks or something. Clearly there is something going on here.