{"id":1342,"date":"2014-11-02T18:50:52","date_gmt":"2014-11-02T16:50:52","guid":{"rendered":"https:\/\/www.planetary-astronomy-and-imaging.com\/?p=1342"},"modified":"2018-09-26T14:49:46","modified_gmt":"2018-09-26T12:49:46","slug":"different-ways-color-imaging-planets","status":"publish","type":"post","link":"https:\/\/www.planetary-astronomy-and-imaging.com\/en\/different-ways-color-imaging-planets\/","title":{"rendered":"Different ways of using colors for imaging planets"},"content":{"rendered":"

The concept of color is often discussed among observers. The purpose of this article is not to debate about the concept of realism, but to describe and discuss the use of three ways to use color for planetary images : “true” colors, “false” colors, and colorized monochrome images…<\/em><\/strong><\/p>\n

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The three ways to bring colors to images : RGB true colors at left, false colors in the middle, monochrome colorized at right.\u00a0<\/strong><\/em><\/p>\n

True colors images<\/span><\/strong><\/h2>\n

We call “true colors” images those realized with the usual RGB or LRGB methods. The notion of “true” colors is a debate in itself but I’m not going to get involved into it here. We will none the less define the colors as translating real physical phenomena, based on each detail’s albedo : colors in this case are objectives<\/em>.\u00a0<\/strong>For example, the Great red spot of Jupiter will appear pink or orange because its clouds absorbs strongly the blue light, less strongly the green and almost not the red.<\/p>\n

True colors images play an important role in planetary astronomy. Because they are objectives, their variations reveal real physical changes on the planets. One of the best known example is the coloration in orange of oval BA in Jupiter in 2006 ; the shift of color from white to orange revealed changes that are still debated, like a higher vorticity and\/or stability, but that are real. There are many other examples.<\/p>\n

Anyway, what you should keep in mind about colors is that they are a code of understanding<\/strong>.\u00a0<\/strong>Colors help us to understand what’s going on on a given planet.<\/p>\n

“False” color images<\/strong><\/span><\/h2>\n

False color images are still putting together various images, but in general we take them outside the visible range (RGB). They are done mostly with infrared and\/or ultraviolet shots. The technique of color processing is the same than for true colors, but in place of red we are going to use infrared, in place of blue, ultraviolet… we may even include CH4 band.<\/p>\n

With false colors, colors are still a code, but an\u00a0artificial\u00a0<\/strong>one, whose purpose is to differentiate the aspects of the details in each one of the original images. But colors in themselves have no importance, they are now\u00a0relatives<\/em>\u00a0: what matters is not the fact that a given detail looks red, what matters is that other details do not look red, or look red as well. The example of Jupiter above made with IR, UV and CH4 could be read like that :<\/p>\n