Why You need to Use a Polarising Filter
Why You need to Use a Polarising Filter?
In this article, we will look at the humble polarising filter. We also explore why you might want to use a polarising filter for landscape photography, the benefits, and some problems you might want to avoid. If you’ve ignored the polarising filter in your camera bag, I would encourage you to take another look.
What is a Polarising Filter?
Light travels in waves and just like the waves on the sea’s surface, these can interfere with each other. When this happens, it distorts the surface of the water and it’s similar with light. Light waves reflecting off surfaces will interfere with each other, and this can cause problems for the photographer.
The role of the polarising filter is to ensure the light waves entering the camera lens travel in the same direction. This prevents the light waves from interfering with each other and allows us to see the landscape more clearly.
The polarising filter is usually round and screws into the front of the camera lens. You can read more about polarising filters on Wikipedia. But please stay with me because I have a lot to share.
Should I Use a Polariser or UV Filter?
A common question is whether I should use a Polariser or UV filter for photography. The answer is potentially both, as they serve different purposes. With modern digital photography, UV filters aren’t essential, although they are helpful in landscape photography to protect your camera’s lens. It’s also possible to simulate the effect of a UV filter digitally to some degree. But with a polarising filter, digital filters can’t reproduce the effect.
If you would like to know more, see my UV filter article.
Types of Polarising Filter
Before we look at how to use the polarising filter, be aware there are two types. There is the linear polarising filter and the circular polarising filter. They both polarise light, but a linear polariser may cause problems.
Early photographic polarising filters were the linear type. These were fine when cameras were manually focused and had no light metre. As camera technology advanced and light metres and autofocus features were added, it was found that the linear polariser interfered with these. If you have an old camera with manual focus and don’t rely on the camera light meter, you may still be able to use a linear polariser. The benefit is that they are often cheaper than circular polarizers.
Circular polarisers (also known as CPL filters) were created to avoid the problems seen with linear polarisers and can be used with most modern cameras. Most circular polarisers are round filters that screw onto the front of lenses. If you see the square filter type that slots into a filter holder, check carefully. These are sometimes linear polariser. Also, if you decide to buy a cheap polarising filter on eBay, check that it isn’t a linear polariser.
How to Use a Polarising Filter
As mentioned above, the circular polariser screws onto the front of the camera lens. It works by having two layers of polarising glass. Each of these will polarise the light waves passing through the filter. Turning one of the layers makes it possible to restrict the direction of the light waves so that all light waves move in the same direction.
You can turn the filter when you have a polarising filter on the front of your lens. As you do this, you will see the polarising effect. If you turn the filter gradually through 360°, you will see the polarising effect come in and out.
But turning the filter isn’t the only thing that affects how strong a response you see. The direction in which you point the lens may also change the effect. For example, if you were shooting a landscape with the sun in the scene, the polarising filter produces little effect when you point the camera towards the sun.
Then point your lens approximately 90° from the sun. This time, when you turn the polarising filter, you will see a significantly stronger effect.
The Polarising Filter Effect
Possibly the best-known effect of the polarising filter is to make blue skies appear much darker. Here is an excellent example on Wikipedia.
When I first started photography, I was in awe at the polarising filter’s effect on blue skies. I used the filter whenever it was sunny (not very often in the UK). After a while, I realised this produced a certain look and stopped using it. What a mistake. It was my technique and overuse that was the problem and not the filter.
Another effect of using a polarising filter is reducing the light level reaching the camera sensor. Whilst this doesn’t produce a direct visual effect, it can extend shutter speeds and blur movement. This makes it excellent for shooting subjects like water. Adding a polarising filter to your lens usually reduces the light by 2 ½ stops.
But there is another excellent reason for using a polarising filter which is why I like them. It can remove surface reflection because it prevents light waves from entering the lens from all directions. Look at the following example.
Here, we can see two identical shots. The image on the left was taken with the camera on a tripod but no polarising filter. A polarising filter was added to the lens, and the second image on the right was taken. To illustrate the previous point about exposure times, the exposure for the image on the left was 2.6 seconds, whilst the exposure for the image on the right was 7.5 seconds. The main point of this illustration is to show how the polarising filter has removed the surface reflection on the water.
Polarising Filter Benefits for Landscape Photography
But it isn’t only reflections on the surface of rivers and lakes that the polariser removes. It’s any surface that’s reflecting light. When photographing woodland or a landscape, you will find the foliage is wet and reflects light. We can remove this reflection by using a polarising filter on a lens. The result is a stronger and more saturated colour, but without appearing unnatural. Here is another example showing two unprocessed raw files.
Notice how the colours in the image on the right are more intense and saturated. This image was taken with a polarising filter on the lens. The image on the left, where a polarising filter wasn’t used, shows a lot of reflection, which has killed the colour.
In addition to improving the colour in a scene with a lot of light reflection, a polariser can help reduce haze. This all adds up to landscape photos with a better colour and detail definition.
Polarising Problems With Wide-Angle Lenses
At this point, you might think you should use a polarising filter on every shot, but that isn’t the case. Some of the features of polarisers, like lengthening the exposure, could cause you issues. For example, you may not want to see movement in your image. Or your exposure time may increase so you can’t capture a steady shot. But there is another problem that is often missed or overlooked.
When you use a polarising filter with a wide-angle lens, you may see dark areas appearing in the sky. Here is an example which I took to illustrate the problem.
This unprocessed raw file was taken using a Fuji XT3 camera with a Fuji 10 to 24 lens at 10 mm. Because I’ve attached a polarising filter to the lens, we can see a dark patch in the sky to the top right of the frame. This is a typical polarising problem when using a wide-angle lens. Because the angle of view is so wide, the polarising effect isn’t seen evenly across the frame.
Please watch out for this when shooting with a wide-angle lens using a polariser. It’s mostly seen in clear areas of blue sky, but you may also see it elsewhere.
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Buy A Quality Polarising Filter
Despite these problems, using a polarising filter can be highly beneficial for landscape photography. But there is a caveat. You need to use a quality polarising filter.
When I started photography, you would need to buy a polarising filter for each lens diameter in your kit. Because polarising filters are expensive, I often looked for the cheapest deals. Unfortunately, these weren’t the best quality polarising filters. After some time, I invested in a 100 mm Lee filter system and found that the filter holder accommodated a 105 mm polarising filter. After some investigation, I purchased a an expensive Heliopan polarising filter. It may have cost a lot, but I could use it with every lens and the results I achieved proved to be well worth it.
Today, I mainly use the Kase Wolverine filter system, which includes a high-quality slim polarising filter. I prefer this because it’s magnetic and attaches to the filter ring. This means it sits extremely close to the front of the lens and avoids the vignetting problems that I saw with the Heliopan filter in the Lee filter system. If you’re considering a polarising filter, I would recommend investing in one of the Kase Filter Holder kits. The filter holder, which comes with a quality polarising filter, is good value. It can also be used with any of your lenses that will take the Kase filters.
You can read about why I switched to and recommend using Kase Filters in this next article.
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