What is T r u e C o l o r ?

Raw Galileo pictures are grayscale images taken in one of eight wavelength bands: violet, green, red, four near-infrared bands (centered at 727 nm, 756 nm, 890 nm and 968 nm) and clear (covering the wavelength range from 410 to 1000 nm). All of the bands are captured by the same camera, but through different filters attached to a rotating wheel that is used to select each specific color. Images acquired with the visible light filters (violet, green and red) can be assembled into a representation of the actual visible appearance of a planet or moon.

The example below shows the individual violet, green and red images from a sequence taken during Galileo's first flyby of Earth in December, 1990. Click on any of the pictures to retrieve a full size image.

Violet Green Red

We can put these three images together to make a color picture. We'll use the red filter image for red, the green image for green light and the violet image for blue. If we give them all the same brightness and contrast, the result looks like this:

"True Color"

Surprised? Because they're so much brighter than water or land, about all you can see are clouds and ice! We can brighten up the picture without altering the color balence:

"Brightened True Color"

However, the previous version is closer to what you'd actually see if you were a passenger on board Galileo!

Okay, I understand what true color is about. Let's see the moons of Jupiter!

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