Mt. Rainier in the Evening

What a difference 12 hours makes in the optics

Still playing with my drone. The evening shots are definitely better than the morning ones; here’s why.

In the morning, the sun is in front of the camera (though high enough to be out of the frame). The sunlight strikes atoms in the air: oxygen, water, smoke, dust, whatever there is, the sunlight hits it and scatters. Scattering is a re-distribution in all directions of the incoming light.

The scattering obscures whatever is on the other side of the air you are looking through. It reduces contrast, hides details, and is generally not helpful for photography unless the scattering itself happens to look interesting. (e.g., a tree casting a shadow that is softened by the scatting.)

Here’s a more detailed article on forward scattering.

Forward scattering has a bigger effect on photography because there’s more of it. Back scattering requires the light to be turned around back to the viewer—and the viewer is a small target, so only a small amount of the actual back scatter reaches you.

Forward scattering, however, requires only a small change in the lights trajectory, and this happens more often.

So while there is some backscattering in the photo above, it’s not enough to obscure the color and form of the distant subjects.

Forward scattering is not always fatal; here is a look in the opposite direction from the above photograph, directly at the sun:

I deliberately used a shorter exposure to limit the brightness levels that are captured. This allows the really bright stuff to be recorded (clouds; sun), and there is only a small amount of visible forward scatter. But look at t longer exposure from a few minutes earlier:

You can see that there is flare (scattering within the camera) as well as some forward scattering within the air. And of course the brightly illuminate clouds near the sun are overexposed.

The good-looking exposures above are, technically speaking, heavily underexposed (by 1 to 3 stops). But the choice to underexpose reveals a better photo, and that is (usually) my most important goal.