Photography Filters Explained: When to Use a Polariser, ND or Graduated ND Filter

Filters are some of my favourite tools for landscape photography because they let me change what the camera sees before I even start editing. But they're also one of the accessories I see people buying without really knowing when to use them.

I've watched photographers put on a polariser because it's a sunny day, or reach straight for a 10-stop ND filter because they think every seascape should have completely smooth water. The filters aren't doing anything wrong. The problem is that nobody has decided what the image should look like yet.

For me, the important question is always: What effect am I trying to create, and will a filter help me get there?

Let's look at the three main types you'll come across in landscape photography and how I use them.

Circular polarising filters: controlling reflections

A circular polariser, often called a CPL, is one of the most useful filters in my bag. Its main job is to reduce certain reflections and glare, which can reveal colour and detail that would otherwise be hidden.

Think about photographing a river running over stones. Without a polariser, reflections from the sky may cover most of the water surface. Rotate the polariser and, at the right angle, you can reduce that glare and reveal the stones beneath.

I also use it in forests and around waterfalls. Wet leaves and rocks can have surprisingly strong reflections, making them look pale and washed out. By reducing that glare, a polariser can bring back the natural colour and texture.

How I use a CPL in the field

1. Compose the photograph and mount the polariser securely.
2. Look through the viewfinder or at live view while slowly rotating the filter.
3. Watch the reflections on water, wet rocks or leaves rather than simply watching the sky get darker.
4. Stop when the balance looks right. I rarely assume that maximum polarisation is always best.
5. Recheck shutter speed, because a polariser also reduces some light reaching the sensor.

Without Polariser

With Polariser

The effect depends on your angle relative to the light, and is often strongest at roughly 90 degrees to the sun. When photographing directly towards or away from the sun, the effect on the sky can be much weaker.

When a polariser can make a photograph worse

I love reflections, so there are times I deliberately don't use a polariser. A reflected mountain in still water might be the whole point of the image. Remove the reflection and you've changed the story.

On very wide-angle lenses, a polariser can also darken one section of blue sky much more strongly than another, creating an uneven band. That can be difficult to correct convincingly afterwards.

The lesson is simple: don't use a filter because it's in the bag. Use it because you want its effect.

Neutral density filters: controlling time

A neutral density, or ND, filter reduces the light reaching the sensor without being designed to change the colours of the scene. That means you can use a longer shutter speed than the available light would normally allow.

This is where filters become genuinely creative. They allow you to decide how movement is represented in the photograph.

For seascapes, I think about three very different possibilities:

• A fast shutter speed can freeze waves and preserve their power and shape.
• A moderate exposure can show water moving around rocks, creating delicate lines and textures.
• A long exposure can soften the sea into smooth, mist-like shapes and make drifting clouds more prominent.

All three can be beautiful. They just tell different stories.

What do 3-stop, 6-stop and 10-stop ND filters actually do?

Each stop cuts the amount of light in half. A 3-stop filter lets through one-eighth of the original light, while a 6-stop filter lets through one-sixty-fourth. A 10-stop filter reduces light by a factor of 1024.

Imagine your correct exposure without a filter is 1/125 second. Keeping the same aperture and ISO, your approximate shutter speeds become:

Filter strength	New shutter speed	Typical effect
No filter	1/125 sec	Freeze much of the water movement
3-stop ND	1/15 sec	Some water movement and texture
6-stop ND	1/2 sec	Flowing lines and softer movement
10-stop ND	8 sec	Strongly smoothed movement

Those are examples, not promises about how a scene will look. Wave speed, foreground shape, wind and the actual brightness all change the result. You can also choose a different aperture or ISO rather than keeping them fixed.

How I decide which ND to use

When I arrive at a seascape, I usually make a photograph without a strong ND filter first. I look at the movement and ask whether I want to freeze it, suggest it or smooth it. If the water is racing around interesting foreground rocks, a moderate shutter speed may preserve far more character than a 30-second exposure.

At times a 10-stop ND gives exactly the minimalist look I'm after. At other times it removes so much of the water's personality that the scene becomes less interesting. Experimenting with different shutter speeds is often more valuable than immediately chasing the longest possible exposure.

No Filter: Freeze water motion

ND 3-stop Filter: Water movement & texture

ND 6-stop Filter: Flowing lines & less detail 

ND 10-stop Filter: Strong smoothed effect

My practical ND workflow

1. Set up the composition on a solid tripod.
2. Focus before adding a very dark filter if focusing becomes difficult.
3. Take a normal exposure and note the shutter speed.
4. Fit the ND filter and calculate the longer exposure using the stop factor or an app.
5. Keep ISO and aperture consistent if you want the comparison to be meaningful.
6. Use a timer, remote release or the camera's built-in long-exposure control to avoid camera movement.
7. Check the first result, including highlight detail and the appearance of the moving water.

If you're stacking filters, pay attention to vignetting at wide focal lengths. Also check for flare, unwanted colour casts and water droplets on the front filter. A single drop of spray can ruin a long exposure surprisingly quickly.

Graduated ND filters: controlling bright skies

A graduated neutral density filter, or GND, is darker on one part of the filter and clearer on the other. It's designed to help balance a bright area, often the sky, with a darker foreground in one exposure.

In a scene with a relatively straight horizon, such as an open seascape, a soft or hard graduated filter can still be useful. But I find traditional graduated filters less practical when mountains or trees rise above the horizon. You can accidentally darken the tops of those subjects too.

Modern sensors have excellent dynamic range, and I often prefer taking separate exposures for the sky and foreground, then blending them carefully in Lightroom or Photoshop. That gives me more control around complicated edges.

It doesn't make GND filters obsolete. It just gives us another option. I choose the technique that produces the most natural-looking result for the scene.

Do you need UV filters or variable ND filters?

For most digital landscape photography, I don't rely on a UV filter to improve image quality. A high-quality protective filter can make sense in dusty or salty conditions, but additional glass can also create flare and reflections, especially when shooting into the sun.

Variable ND filters can be convenient when you want to adjust shutter speed quickly, particularly for video. For still landscape photography, I often prefer fixed ND strengths because they're predictable. Variable filters can produce uneven darkening or cross patterns at extreme settings, especially with wide-angle lenses.

What I carry

For my landscape and seascape photography, a circular polariser and a small collection of fixed ND filters cover most of what I need. I've used NiSi filters extensively, including the JetMag Pro system, because I value being able to change filters quickly in difficult conditions.

But the brand matters less than understanding the effect. A well-used polariser is far more valuable than a collection of expensive filters you don't understand.

An exercise for your next outing

Find a stream, waterfall or seascape with interesting movement. Keep your composition identical and make four photographs: without a polariser, with a polariser, with a short ND exposure and with a longer ND exposure.

Compare them carefully. Ask what changed in the colour, reflections, textures and mood. Which version tells the story you want to tell?

That question is much more useful than asking which filter is “best”.

Final thoughts

Filters aren't there to make every landscape look dramatic. They're there to give you choices. A polariser can reveal hidden colour, an ND filter can change how you represent time, and a graduated ND can help manage contrast in the right scene.

Once you understand what each one actually does, the decision becomes part of your creative process rather than another setting to worry about. And that's when filters start becoming genuinely useful.