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Earth "Real" Blues

posted Sep 25, 2011, 11:48 PM by Abel Mendez   [ updated Sep 26, 2011, 7:29 AM ]
Our vision is not only limited by the energy range on the visible spectrum but also by its sensitivity to particular colors. The eyes are more adapted to see green/yellow light than red and blue, a consequence of evolution. A simple experiment with three lights with exactly the same intensity (measured by instruments) of red, green, and blue, will look to the human eye as the green is the brightest, then the red and the blue last. This "distorted" reality is unnoticeable to us in our daily life and is called True-Colors for its electronic representation. But how the world will look like without this limitation? And when I say world, how Earth "really" looks like with its natural blue tones? Short answer: looks prettier and bluer.

    We are developing code to generate True-Color visualizations of exoplanets as part of our Scientific Exoplanets Renderer (SER). SER uses physical inputs from planetary properties to recreate visualizations and some times the output is not as expected. For example, water is able to scatter blue light given it a bluish tone on large quantities like oceans, so it should generally look blue also in any exoplanet (unless mixed with other stuff). However, under a dimmer red star less blue light is available and our simulated oceanic planets started to look black, although physically their color was supposed to contain some blue. The simulations were right, our eyes were deceiving us, we lost the ability to distinguish blue tones under low light.

    We developed an image filter to compensate for the eye limitations in recognizing red and blue tones. Our Physical-Color filter convert any image to its 'real' or 'physical' colors as seem with eyes with a normalized response to chromatic light. This filter provided a solution to our visualization of exoplanets during the development process, by allowing to better recognize how changes in physical properties correlate with visual changes. In the end, the main idea behind the visualizations is to show the planets in True-Color, our "reality," instead of Physical-Color, but they look very interesting too. Here we show three converted images as examples (Figure 1-3). The filter intensifies the reds and specially the blue tones, not altering the greens or the whites, in a physical way to compensate for the eyes limitations, and recreate the look of the world we are missing.


Figure 1.
 Comparison of NASA Earth Blue Marble image of the Eastern Hemisphere in True-Color (left) and Physical-Color (right). Much more details in the ocean colors and the coast depth is visible now in the Physical-Color reconstruction.


Figure 2. Comparison of NASA Earth Blue Marble image of the Western Hemisphere in True-Color (left) and Physical-Color (right). Much more details in the ocean colors and the coast depth is visible now in the Physical-Color reconstruction.


Figure 3. Comparison of a Pleiades image in True-Color and Physical-Color. More details of the gaseous components of the system are visible, and more red stars are also visible now in the background.