For most PlanetScope 2 imagery the value of the blue white point will end up more or less midway between the red and green white points. To adjust the curve, click and drag on it, or click on a point and use the arrow keys to change values one at a time. Changes that increase the relative amount of green make the image more green (obviously) while changes that decrease green shift the hue of the image towards magenta (red + blue). Adjusting this curve will modify the green channel alone, which allows you to change color of an image, not just brightness and contrast. This will reveal a green curve (that starts as a straight line) and a green histogram. Pick the green band from the drop-down menu labeled “RGB”. When you add additional points and bend it, you’re making nonlinear adjustments.) As long as it’s straight you’re making linear adjustments. (The white point is the open square on the top right of the diagonal white line in the curves palette. Fix this by adjusting the white point of the green band independently of red and blue. That said, how do you change an image of Beijing from this:įully saturated pixels appear white, pixels saturated in blue and red are magenta, etc.Ĭlose, but you can tell by the remaining blue and magenta fringing surrounding the fully-saturated areas that there’s not enough green. In practice, these three elements are inextricably linked-changes in one facet affect the others. Brightness and contrast together can be considered tonal adjustments. It’s not a process of making a scientifically accurate picture-our visual system is too non-linear, and too mutable.Ĭonceptually, you can break color correction down into three facets: brightness (the overall level of light in an image), contrast (the relative light levels of adjacent areas in and image), and color balancing (adjusting the overall hue of an image). For the very best results, do it by hand.Ĭolor correction is the process of adjusting raw image data so the resulting picture looks realistic. This image may be reproduced and distributed freely.įinally, satellite images of the Earth need to be adapted to the dynamic range and color gamut of display technologies (both screen and print), which are quite limited compared to the real world.īecause of this, it’s very difficult to do automatic or universal color corrections. The squares marked A and B are the same shade of gray.
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