How to use a polarizing filter for landscapes

A circular polarizer (CPL) isn’t a neutral-density filter — it doesn’t exist to slow your shutter, though it happens to cost a stop or two of light as a side effect. Its actual job is cutting polarized reflections: the glare bouncing off water, wet leaves, and haze that a plain lens can’t avoid.

The one thing that decides whether it works: the angle to the sun

A polarizer’s effect is strongest when you’re shooting at 90° to the sun — sun to your left or right, not behind or in front of you — and fades to nothing pointed directly at or away from it. Rotate the filter while looking through the viewfinder or at live view and you’ll see the effect sweep in and out as you turn it; stop rotating at the point it looks best for the shot, not at a fixed mark.

This angle-dependence is also why it can misbehave on very wide lenses: the sun’s angle relative to different parts of an ultra-wide frame varies enough that the sky darkens unevenly, deep blue on one side of the frame and barely affected on the other. If that shows up, back the effect off by rotating toward neutral, or skip the filter for that particular wide shot.

What it actually does

• Deepens blue sky and makes clouds pop — polarized skylight is what a polarizer cuts, so a clear sky at the right angle goes noticeably richer and cloud detail stands out against it.
• Removes glare from water and wet foliage — this is the effect landscape photographers reach for most: cut the reflected glare off a lake or stream’s surface and you can suddenly see into the water instead of a mirror of the sky, and wet leaves after rain saturate instead of looking washed out with reflected sheen.
• Costs roughly 1–2 stops of light — a side effect of the glass, not the point of the filter, but worth accounting for in your exposure the same way you would a mild ND.

When to leave it off

Skip it (or dial the effect back) when: the sun is behind or in front of you, where it does nothing useful; on an ultra-wide lens where the sky darkens unevenly; or when you specifically want a reflection in the shot — a polarizer set to maximum effect will remove the very reflection you’re trying to capture in, say, a still-water symmetry composition.

Gear

A circular polarizer sized to your lens’s filter thread (or held in front of it in a filter-holder system). No other gear required — unlike ND work, there’s no separate calculation to make; just rotate and check the viewfinder.