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."

Comments

Digicams and colors

[mwburden]

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!

Re:Digicams and colors

[mks113]

All CCDs are particularly sensitive in the IR range.
Video Cameras and digital cameras have to filter out this sensitivity to get true colour.

Sony uses this IR sensitivity in their "Nightshot" feature on vidcams. Instead of filtering out the IR component, they use it. It throws off the colour rendition but uses ambient and generated IR to show stuff at night.

I was at a lodge in Kenya just after dusk, and was told that there was a leopard in at a baited tree across the river. It was too dark for me to make it out, so I set up my camera on a tripod, and quickly had a crowd around the LCD watching a very clear picture of the leopard!

And I discovered years ago that a CCD vidcam will show the light from a remote. I've used it quite a few times to verify that a remote is actually working.

Re:Filters vs Bayer

[Anonymous Coward]

Look, all I want to know is what my eye would see if I were standing on Mars. Can't someone just cut through all this BS "science" and tell me that?

Bitmapped horizon

[l0wland]

Can anyone explain to me why the horizon of the hi-res images is bitmapped ? (beware, pic in link is 12MB in size)

Aside of the odd colors, I found this one of the most interesting anomalies in the pictures so far.

Re:Bitmapped horizon

[l0wland]

That's just an artifact of the JPEG compression that was used on the images.

That's what I thought too, until I tried to reproduce that. Try it with Photoshop or another photo-editing app, you will not be able to get a sharp pixelated line like that when using JPEG-compression.

That should read as: At least I couldn't :-)

Re:Conspiracy theorists

[Simon Hibbs]

>I have read literally dozens of things that ``prove'' the moon landings were faked, for
>example, and each one is rather easily shown to be wrong by anyone with experience in such things.

My favourites are the 'pictures of alien moon bases'. Many of these prove to be blowups of astronomical JPG files. The compression algorithm used in the JPG format introduces artificial distortions in the details of images, so it's not surprising they find all sorts of weird looking shapes when they magnify the pictures.

Simon Hibbs

The Blue Skies of Earth

[NickFusion]

Not to do anything crazy like bring the artcle into the conversation, but the uncalibrated RGB raw data that the mars rover sends back, and the methods used to color correct it reminds me of this:

The Russian Record

This brilliant Russian photographer in the late 1800s/early 1900s took an amazing number of photographs, and he would photograph everything three times, with a red, blue and green filter.

He would then use a special triple projector with the appropriate color filters to show gorgeous color images, long before the invention of color film.

So today, we can put these images back together in Photoshop, but we have the same Mars problem, we have three color channels, but no clear idea how they relate to each other.

Lacking a color-calibration sundial, we have to rely on our knowledge of skin tone, sky color, etc to tweak these colors. The link above has a link to the raw files in the Library of Congress, for geeks who want to recomposite some of their own.