Originally posted by ZiggyMojo
reply to post by exponent
Tons of black and white images from previous missions to mars...
First you need to realize that ALL digital camera light sensors (the camera's CCD) are color blind
; they can only detect (i.e., "see in")
gray scale -- even your consumer digital camera's CCD is color blind.
Let me explain. The way digital cameras produce color is by viewing an image through various filters (Red, Green, Blue), or more commonly through a
single combined RGB filter called a "Bayer Filter". Each picture you take goes through that filter before striking the CCD light sensor (which, as
I said, can only see in shades of gray). The color of light passing through those filters is read by the CCD as different shades and intensities of
gray. Computer algorithms inside your camera then compares those gray scales as seen through the different RGB filters, then translates those
different intensities into what it thinks the actual color is -- based on what science knows about color and gray scale intensities.
This all happens quickly in your camera, and what you end up with is a "color" JPEG in less than one second. However, that color has been
interpolated from gray scale information. A "RAW" file (which some better consumer cameras can output to you) would give you the three color
channels (RGB) prior to JPEG interpolation.That RAW file would contain more information about the image than the interpolated JPEG file, which creates
a lossy file (a file with lost data).
That takes us to the Mars Rovers black and white images. The Mars rovers take each image multiple times as viewed though multiple and various filters
of different wavelengths of light. Instead of it working like your consumer camera -- i.e., doing the combining of the various filtered images and
interpolating the color INSIDE the camera, the rovers send those raw images (as seen through the various filters) back to Earth so they could be
processed here instead.
Those images are then processed in color here on Earth, and some of those color images submitted to the public. However, if you look at the raw
images from the rovers, all you see is the gray scale.
Imaging scientists like this because it gives them more flexibility to process the images different ways to contrast different types of materials to
make them stand out against other materials (the "false color" images we often see.
The twin MER rovers (Spirit and Opportunity) worked this way, but the new rover (Curiosity) has a Bayer filter built into the Mast Cam and MAHLI
camera, so the pictures transmitted back to earth can be seen in color.