Helping a Mountain Shake Off Its Blues

Or: color can be changed in a photograph

Air seems, most of the time, to be quite clear. Unless such things as fog, clouds or smoke get into the air. Then the things in the air make the things on the other side of the air that much less clear.

But the air itself is not without guilt in this. Firstly, we note that the sky is blue. That is not quite the same thing as clear. If you look at the photos of Rainier in my last post, the mountain has quite a strong blue cast. So we have established a well-noticed but often not bothered-with fact: the air is clear, but also blue. Or makes things look blue, or something.

(Blue light is scattered more than other colors, so nothing is blue; the blue light just gets ‘promoted’ as it were and takes over; the other colors remain un-promoted, and blue wins by default.) (Click for more.)

However, a clever person at a computer can subtract that blue light and re-balance the colors, revealing ‘what is really there’ (we hope it is really there). The image above has had its blue surgically removed using the program ‘Capture One’ on my Mac. The blue caused by the biased light-scattering powers of 25 or so miles of air molecules between camera and mountain has been neutralized. (Unfairly to the wisps of vegetation at the bottom edge, which without their blue color look rather yellow.)

So: just as light can be preferentially colored by the amazing translucent bits on butterfly wings, it is routinely color blue by the properties of those gaseous atoms which we breathe. And in both cases, the color comes, not from the color of things, but from the fundamental atomic-level properties of photons and physics.

You may ask: if I took the blue out, why is the sky behind the mountain still blue? Well, I only took out the equivalent of 25 miles of blue; there’s another few hundred miles of blue left in the rest of the sky. If you want that out, well, you’ll need your own computerized detergent; I’m quite satisfied with 25 miles worth (not that I really need any more blues here in Seattle in the winter!)

If you haven’t seen the still-has-its-blues photo of the mountain, it’s here in this post.