A polarizing filter often improves an image by reducing glare and reflections, which are frequently polarized. That glare is usually the color of the light source (often whitish sky/light) rather than the true color of the subject.

When reflective glare is added to a subject, it washes out detail and lowers contrast. For example, on water, glass, painted surfaces, or foliage, the camera may record both the subject’s actual color and a bright reflected layer on top of it. The result is a paler, less defined image.

By rotating a polarizer to block much of that polarized reflected light, you reduce the unwanted bright overlay. That lets the subject’s own color and texture show through more clearly, so:

• contrast increases
• colors appear more saturated
• detail becomes easier to see
• exposure and flare issues from bright reflections may be reduced

It doesn’t magically sharpen the image; it mostly improves clarity by removing stray reflected light that masks detail.