How To Use a Circular Polarizer

If someone told me that I could only use a single filter for the rest of my life, I would answer ‘circular polarizer!’ before they even finished their question. If used correctly, it makes such a great difference to an image that people often use its effect as an analogy to justify extreme photoshop manipulation. In simple terms, it saturates colours and enhances contrast, but depending on when and how it is used, this difference can vary from a small enhancement to creating a totally different photograph. If used incorrectly, it can completely ruin a photo, so it is important to know the basics to getting the most out of your circular polarizing filter. I will abbreviate it to ‘CPL’ going forward.

 

What exactly does a CPL filter do? This is not a simple matter and one that deserves an article of its own. You can watch the below video on youtube and see if it makes sense. The shortest and simplest explanation is that it filters out light with ‘damaged’ polarity.

Understanding the science behind it is luckily not a prerequisite for knowing how to use it, so we’re going to focus on the how and not the why. There are several guidelines for when and how to use a CPL and a few critical situations when not to use it.  I’m going to explain the most popular uses along with visual examples to show you the power of the polarizer.

Circular vs. Linear 

This is an age-old question, but the answer is simple. Linear polarisers are older tech and they confuse modern light metering systems. Stick to circular.

What is the visual effect of a CPL?

Most articles on CPLs will tell you that it is used to remove reflections and glare and while technically correct, these are very poor descriptors of the visual effect it has on scenery.

For those who have never seen or handled a CPL filter, it is worth explaining that any screw-in CPL consists of two rings, the rear ring is just the screw thread, while the front ring contains the actual filter and can rotate freely from the rear ring. Once installed, this allows the filter to be rotated while installed on the lens. A CPL filter’s effect varies at different angles, so being able to rotate it is a critical part of achieving its function.   

Is there an ideal rotation position? 

No - if you look on the side of a CPL for some mark indicating optimal rotation, you won't find it. There are too many factors at play like the shooting direction, position of the sun and personal taste. 

Enhancing the Sky | The 90 Degree Rule

A CPL has the maximum effect at an angle of 90 degrees to the sun. If you look North or South in the morning or afternoon and rotate it to its optimal angle, you will see that it makes the sky a dark cobalt blue.

 

At this point it is important to differentiate between the sky and clouds as we generally refer to everything above the horizon as being the sky. The magical effect of a CPL lies in the fact that it only darkens the blue sky – i.e. Not the clouds. By darkening only the patches of sky in between the clouds, it can greatly enhance the contrast. It adds critical shadow tones and makes the clouds stand out against the blue sky. Ever wondered how stock photos get those crisp, puffy white clouds against a deep blue sky? The vast majority of those images were taken with a CPL. 

Namib Rand | Hougaard Malan - See how deep and dark the blue sky is amongst the clouds? This photo would be much more flat and lacking in contrast if it was shot without a CPL.

No Clouds Around?

Even without clouds it still offers a great benefit by making the sky several stops darker. If you look at so much of the best landscape photography around, you will see there is a certain recipe that repeats itself over and over – strong light below a dark moody sky. Because we are used to the standard tones of everyday life – a sky brighter than the land, when that relationship flips and the sky is darker than the land, it gives an incredible eye-catching impact to an image. A circular polarizer can darken a clear sky and that accentuates the textures, shapes and lines in the land.

Eliminating Haze | Saturating Colour | Enhancing Clarity – Large Vistas

In order for an image to be produced, sunlight reflects off the subject and then travels towards your lens to be captured by the sensor. On this journey between subject and lens, some of the light reflects and refracts off particles in the air and its polarity becomes compromised. The greater the distance and particles in the air – the more colour, contrast and clarity you lose. A circular polarizing filter can remove the damaged light, allowing only the uncompromised light through in order to produce an image with better contrast, clarity and saturation. Below is a simple example of the difference that a circular polarizing filter can make on a grand scene, if used correctly.

Removing Reflections

This can have several creative effects, some obvious and some not so obvious.

A CPL is immensely useful for car, product, interior and architectural photography where reflections on glass or glossy surfaces are mostly an unwanted distraction. We are of course a nature photography oriented brand, so we will focus on the effects in landscape photos.

The most obvious use of a filter that removes reflections is the ability to see through water. This is a fantastic feature for seascapes, river scenes and rock pools, where the scene below the water can form a critical part of any composition. Simply turn the CPL to the desired angle in order to remove the reflection.

 

A less obvious use for removing reflections is the saturation of foliage. The reason that foliage is much more colourful through a polarizer is that most plants’ leaves have a glossy surface, which reflect a lot of light and the light becomes damaged in the process. Anyone who shoots forests frequently will know that a CPL is as critical as the memory card or battery in your camera. 

 

Enhancing Rainbows

There’s not much to elaborate on here. Turn a CPL to its optimal position and it will give you about a 20% boost in rainbow contrast and saturation.  

 

Perito Moreno Glacier | Hougaard Malan

The Cardinal Sin – Wide angle and Clear Skies

This is where most beginners to a CPL bump their heads. The sky has a natural tonal gradient caused by the angle at which the sun hits the atmosphere. A CPL exacerbates this gradient and if you use the filter at optimal rotation, it creates a very dark radial spot in the sky, as pictured below.

The wider you shoot, the more obvious the uneven tones in the sky.  There are several ways to mitigate the effect and this knowledge is critical to getting the most from a CPL – read the below points. This dark spot has NOTHING to do with the quality of your CPL – a more expensive filter will not improve it.

Boats washed up on Melkbos Beach in 2007 | Hougaard Malan

Mitigating the Dark Spot

1) Longer Focal Length

By shooting at a longer focal length, you include a smaller area of the sky, which means that there will be less tonal variation and it will thus look a lot more natural.

2) Hide it behind clouds

Clouds can work absolute magic to hide that dark spot as it will camouflage the worst of it (hopefully) and only reveal the slightly darker tones in the surrounding area, or only some of it in the gaps visible through the clouds.

3) Piggyback on an existing natural tonal gradient

If there is already a strong natural side-ways gradient in the sky, then you can get away with the uneven tones created by the CPL to a great extent.  This typically occurs when you shoot a cloudy sky with sunlight pouring in from the side. This creates the expectation that there should be a light-to-dark graduation of tones due to the sunlight coming from one side and it mitigates the effect of the CPL. 

4) Don’t use full polarization

It is common advice to only use a CPL at about 75% of its potential as a safeguard against the dreaded dark blue spot. While this is good advice for beginners or less attentive shooters, I don’t like advocating it as a concrete rule. As explained above, there are a lot of situations in which you should make full use of your CPL’s ability as long as you are paying attention. If you want to shoot fairly wide and there aren’t any clouds around, then it can be useful to only use your CPL at a reduced amount, but in all other situations, interpret the conditions and make an informed decision.

5) Use the radial gradient in Lightroom

If you’re a regular with the radial gradient filter tool in Lightroom, then you can use this to lighten the dark spot. 

Does a CPL filter affect exposure? 

A CPL filter is roughly 1.66 stops dark, so there is a slight compromise in exposure in situations where shutterspeed is critical. In landscapes, particularly where moving water is involved, this is normally to your benefit as it acts as pseudo-ND filter. A common misconception is that a CPL’s density varies with rotation and while this is to a very minor extent true, it is not a range of 0 – 1.66 stops as it is rotated. It is typically only about a 0.33 (3^rd) of a stop difference. If using it as a pseudo ND filter, your primary concern with rotation should be the visual effect on the scene and not whether it is giving you a longer shutterspeed at various rotation positions.

Arniston | Hougaard Malan - The ND effect will slow down shutterspeed and assist in creating soft streaky patterns in the water 

Does a CPL affect image detail/sharpness?

In theory, any filter you put in front of your lens should compromise image quality to some extent. This is however where the quality of the product comes into play and it is important to avoid cheap brands that you’ve never heard of. There are a few criteria to consider when deciding on which CPL to purchase.

We invite the passionate pixel peepers to scrutinise these RAW files. All three were taken on a Fuji GFX100 with 63mm f/2.8 at f/5.6. There was a slight breeze blowing, so ignore the foliage - look at the tree trunks. Each file name is labelled according to the filter used. There is a very slight difference in sharpness, but the fact that it is barely visible on this camera and lens combo shows how small it is; it will most probably be imperceptible on 35mm full frame sensors or anything smaller. It does however show that if you're shooting in situations where you need to get every single drop of micro-contrast and resolution, it might be better to shoot without any filters. 

• Image 1 - No Filter
• Image 2 - NiSi Pro Nano HUC CPL
• Image 3 - NiSi Titanium Alloy Landscape Enhanced CPL

Friendly Warning - over 600MB file size. 

 

Material of Filter Ring/Casing

The metal that the filter casing is made from determines strength and weight, but also whether you will one day end up in a tug of war to get a jammed filter from your lens. The primary cause of jammed filters is overtightening by the user, but the material also plays a role.

1. If the packaging or product description does not specify, then it is likely made of steel or a cheap alloy and you want to stay very well clear of these.
2. The next best option is aluminium, which is light and strong, but not very malleable, so if it gets jammed, you are going to have a tough time getting it out.
3. After aluminium comes brass, which is the most common material you’ll find in a good quality CPL. Brass is strong and light, but very malleable, which makes a jam unlikely.
4. Some progressive brands are now moving to alloys made of titanium combined with a softer metal to improve malleability, which prevents jamming, while offering better strength and weight than brass or aluminium.

Thickness

If a screw-in filter is very thick, it will show up in the corner of the frame when used on a wide angle lens. It is thus important that the filter is fairly thin. It shouldn’t be paper-thin, but some of the cheaper CPLs can be up to 10mm thick, which is problematic as you will have to crop away those corners. 

Coatings

This is an extremely underrated performance area that makes a substantial difference. Most filters have multiple nano-coatings that perform various tasks. It is critical that a filter has excellent hydrophobic qualities and does not wear easily. You should be able to clean a filter with a quick circular wipe of a dry microfiber cloth. If you have to wipe it for 30 seconds and it still looks dirty, then you know something is wrong with the coating OR your cloth is wet/oily. If you shoot at the coast or like to shoot stormy weather or waterfalls, you’ll have to deal with water on your filters on a regular basis. It is also important that these coatings don’t wear too quickly, because regular wiping and particularly hard and repetitive wiping will put micro scratches on the filter and before long you will have to throw it away due to flare and soft spots in your images.  These factors will be the difference between loving or hating your filter.  

How water should bead on a premium hydrophobic coating

Square vs. Circular

Circular filters offer a much lighter, compact and more affordable entry to filters for those who are scared of committing to a square system from day 1. If you think ahead, then you might have already stumbled on the thought of ‘what happens to my screw-in filters if I upgrade to a square system’? That is a very important question that fortunately has a good answer.

While square filter systems are only for those who are seriously into landscape, seascape or architecture, screw-in filters are a must-have for everyone, even those who own a square filter system. Square systems are great for the typical landscape shooting style – slow, methodical and precise; always on a tripod. The moment that you remove the tripod from the equation, a square system is a pain to use. There are also many situations where a square system is too large to travel with or too cumbersome to use. Think travels with luggage limitation, shooting from game drive vehicles, hiking or walkabout shooting…the list goes on. 

I absolutely love my square filter system and would never go without it, but there are too many situations where it is just not practical and for those situations I have screw-in polarisers as well as 3-, 6- and 10-stop IRND filters. Hence I always advise beginners to start with circular, see if they like it and then add square to their arsenal at a later stage. You will always have a use for high end screw-in filters, but, what is a waste of money is cheap low-quality filters, particularly when it comes to square systems and that should be avoided at all cost.

NiSi’s Offerings

As of October 2020, NiSi offers three different CPLs, each with a key difference. The primary difference lies in the colour tone and choosing should be fairly easy. 

It all comes down to personal taste and deciding whether you want a cool or warm tone or to keep all colour enhancement to the computer. Find more info and side by side comparisons in this article comparing the versions by Matt Bouch. 

 

 

Their Pro Nano Standard CPL is exactly what you’d expect from a high-end filter – a brass ring construction, near-perfect light transmission, fantastic anti-scratch coatings and one of the industry’s best hydrophobic coatings. It has a slight warming effect, a popular trait in CPLs, and it protrudes 4.5mm above the lens it is fitted to, which is very thin.

• 46mm @ R799.00
• 49mm @ R899.00
• 52mm @ R999.00
• 55mm @ R1199.00
• 58mm @ R1 299.00
• 62mm @ R1 499.00
• 67mm @ R1 499.00
• 72mm @ R1 599.00
• 77mm @ R1 699.00
• 82mm @ R1 899.00
• 95mm @ R2 899.00

 

Their Titanium Alloy Landscape Enhanced CPL is a fairly new offering and a welcome addition to the market. For many years now, most manufacturers have made CPLs with a warm tone. NiSi decided to go against the current and release a CPL with a cool tone. This filter has a stronger polarization effect than normal CPLs, giving more contrast, clarity and saturation. The result of the cool tone and extra punch is fantastic for any landscape with water or clouds – it gives the water and clouds a crisp and fresh feel by making the water and sky a touch bluer and ensuring that clouds are a cool, contast-rich white.

This filter is one of the first on the market to feature a Titanium alloy ring – a feature that makes it stronger and lighter than any offerings from the competition. Use the slider below to see the difference between the two different CPLs. 

• 67MM @ R1 999.00
• 72MM @ R2 199.00
• 77MM @ R2 399.00
• 82MM @ R2 599.00

 

Their Pro Nano Natural CPL has no colour tone and renders colours true to the original scene. It’s important to keep in mind that polarization changes certain colours slightly, so if you pixel peep you will come across some difference and that is all natural and nothing to worry about. 

The Natural CPL features a unique two-tone frame with a silver front ring, black back ring and both are made from high-quality aluminum.  NiSi’s Natural CPL utilizes Cine seal technology which blackens the edge of the CPL for added durability. This technology reduces the influence of temperature fluctuations and keeps out condensation.

• 46mm @ R898.00
• 49mm @ R1139.00
• 52mm @ R1299.00
• 55mm @ R1449.00
• 58mm @ R1 499.00
• 62mm @ R1 799.00
• 67mm @ R1 949.00
• 72mm @ R2 049.00
• 77mm @ R2 149.00
• 82mm @ R2 299.00
• 86mm @ R2 799.00
• 95mm @ R3 449.00

Don’t become a polarizer junkie!

 #CPLaddiction is real. Once you get hooked on that extra contrast and colour it gives to an image, you’ll be tempted to super-glue it onto your lens. Go through the learning curve, see where it works and also learn where it doesn’t. Always avoid the dark blue spot and take it off once it is too dark as 1.66 stops is a lot when your shutterspeed approaches minutes.

Newcomers vs. Old Brands

The boom in the popularity of filters has put a lot of new manufacturers on the market and there is a very important aspect to this that is worth considering. In the middle tier, there are about 5 mainstream brands that have been around for decades and those who have been following them for 10-20 years will know that they haven’t had a single product announcement or so much as a packaging update in those two decades. Most of these are a textbook example of a company resting on its laurels, riding an age-old reputation to sell extremely outdated technology. Much of the advancement of filter tech has happened over the last 5 years in the field of nano-coatings, so a lot of the newer brands on the market have much better hydrophobic coatings and light transmission.

Price

This is an area of great confusion as 90% of people follow the assumption that the higher the price, the better the quality. An important factor to understand is that the market for circular filters is gigantic and it is extremely contested by manufacturers and distributors. The older manufacturers who have large market share and distribution and sales channels in place can charge a high price and get away with it. The younger manufacturers, who often have a better product, have to compete on price to try and steal market share from the veterans. Looking at price is thus not always the best benchmark of quality. There is also the issue of where it is made – Asian countries can make the same quality filter as the US and Europe for half the price, which again deviates price and quality from each other. The square filter market was dominated by European brands until about 5 years ago, but the Chinese have managed to pluck it from their hands in a few short years. Those Chinese companies are now putting their tech into circular filters and targeting that market. As explained above, they are working their way in by competing on price, so Chinese circular filters are currently selling at a substantial discount. Do your research and speak to the photographic community before committing to a brand – buying into the old brands that have been there for 20 years might not be the best value for money anymore. Where things go in the next five years will be interesting to see.

Do not misconstrue the above as advice to buy dirt-cheap filters. If you go below the R1000 mark for a 77mm CPL, you are venturing into questionable territory!

Do you have any questions? Get in touch using the chat app or contact page.