In case you're unfamiliar with polarizing filters, they are the same as polarizing sunglasses, taking advantage of some optical physics trickery to cut down on light specifically from reflections – reflections from glass, from asphalt, from the surface of water, from any source – at the cost of a 1 to 2 stops of light darker image.
In this particular instance, the polarizer was able to cut through the reflections on the surface of the ocean and see down through the water to the sand beneath, dramatically altering the composition of the photo. Whether the effect is desirable or makes the photo "better" is subjective, but here we can at least see what the effect does.
The particulars of the hardware here involved a Fujifilm X-Pro2, the XF 55-200mm lens, and Hoya NXT Circular Polarizer.
Sample 1With no polarizing effect With the full polarizing effect
Sample 2With no polarizing effect With the full polarizing effect
Sample 3With no polarizing effect With the full polarizing effect
You can see in these examples how the polarizer was affecting the colors and contrast in the image, primarily in the surface of the ocean, but also in the trees and even slightly on the rocks.
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