To understand this issue, we need only four photos and a few sentences to describe each of them.
Typically cameras are 12-bit, but the resulting images are compressed to 8-bit using a technique called “companding”.
The result is images of artificial color, but this method of photography is extremely popular due to the fact that compression reduces the amount of data, which means it increases the speed of transferring images from Mars to Earth.
It is noteworthy that knowing the intricacies of the compression method, a team of specialists is able to give the image real colors without loss.
Decompressed (decompacted) version
This is, roughly speaking, a view through the “eyes” of the spacecraft, taking into account the various filters and sensory capabilities of the cameras.
The result is a close, but still not natural color.
Natural color is achieved by calibrating the image using radiometric brightness characteristics and corrections for individual pixel features.
Such images give an idea of what you would see with your own eyes if you were in the place of the rover.
Sometimes white balancing is applied, which allows you to achieve the effect of “earth conditions”.
The result is images with white and blue skies and landscapes reminiscent of some kind of desert on Earth. The effect of “earth conditions” is necessary to simplify the identification of rocks.
It is worth noting that natural processes, such as the angle of incidence of sunlight, atmospheric conditions, dust / haze, mineral composition, etc., can also affect color variations.
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