Circular polarising filter CPL in your smartphone photography explained – tips

Love experimenting with your iPhone and Android camera and learning new techniques – me too!

 

This article will explain the magic behind the circular polarising filter – because it really does feel like you are cheating! After the tripod and a wide angle lens – the next most important accessory is this filter also known as a circular polarising lens CPL.

 

The results are immediately obvious and armed with some non-jargon theory – in no time, you will be getting the most out of this circular polarising filter in all your photography.

What is polarising light

As you can probably guess, a circular polarising filter has the purpose of filtering polarised light. I am going to get technical for a moment – however, this will be a very simplistic explanation.

 

A circular polarising filter allows a certain angle of light to pass through the lens. This adapted glass is coated and has tiny slits in them that block out light that travels horizontally across them and only passes light that travels vertically through them.

 

Using the below analogy of a comb:

A circular polarising filter is similar to a comb having vertical teeth. These slits only allow vertical light waves to enter (card held on its side) and blocks out all other wavelengths that try to enter from all other directions.

Light travels as waves that can be vertical, horizontal and any which way in between – hitting our eye and smartphone lens at varying angles. When light is reflected off a non-metallic surface and water, the light waves mostly become horizontal – creating glare and reflection. Glare does not take on the colour of the reflected material and instead is seen as white. This mutes the natural, vibrant deep colours of the material. This is more evident in blue and green colours.

how do polarizing sunglasses work - similar to a circular polarizing filter for the iPhone and mobile smartphone

Benefits of a circular polarising filter

  • Reduces haze – made up of particles in the air that reflect light. The circular polarising filter eliminates the haze
  • Reduces and recovers highlights – smartphone like all cameras captures a limited dynamic range of light. The first light the camera sacrifices is the bright sky. The circular polarising filter recovers these details and brings details back into the bright areas
  • Adds drama in clouds – darkening and bringing details in the clouds, adds drama to the imager
  • Captures more colour – sun glare is always white. This reflection produces muted colours. The filter captures deeper, more vibrant colour
  • Removes reflection – capture the scene under the reflective water surface, reduce reflective skin in portrait. Ever captured a travel photo from a tour bus and captured the reflection of the seat in front of you?
  • Reduces shutter speed – similar to a neutral density filter, the circular polarising filter lets in less light providing you more scope to manually alter ISO and shutter speed for creative long exposure results
The NiSi Prosories graduated neutral density filter and polarizing filter reduces reflections in glass and water - smnartphone photography

Circular polarising filter options:

Struman Optics circular polarising filter

This circular polarising filter by Struman Optics is attached via the adaptor ring to either the Cinematic portrait or Cinematic wide-angle lens (post-June 2019).

The filter extends the already impressive lens to further increase the capability of your smartphone camera.

Arrives in a small protective case for portability and convenience when storing. The prevent accidental damage. The lens hood can alternatively be attached to protect the lens from damage.

Struman Optics Cinematic circular polarising filter CPL together

NiSi P1 Prosories smartphone filter kit

This universal holder can be rapidly attached to any iPhone, iPad, Android smartphone or tablet. Included in the kit are the Graduated Neutral Density Graduated (GND) and circular polarising filter. These filters can be used individually or stacked in the holder to combine the advantages of both filters.

 

For the techies – the GND filter is a 3 stop and polarizing lens a 1.5 stop, totalling a 4.5 stop reduction. This provides more scope for manual, creative control using either Pro mode on the Android or a camera replacement app on the iPhone.

Quick techniques:

  • Rotate the circular polarising filter to increase/decrease the effect
  • Switching between portrait and landscape orientation – rotate the filter
  • Experiment incrementally spinning the filter – no need to go the full effect

Pitfalls:

  • As mentioned above, the polariser works best at 90 degrees to the sun. A wide-angle lens takes in more than a 90-degree angle to the sun – therefore deviations either side can produce unnatural transitions between lighter and darker areas in the sky (banding). If this occurs, turn the polarizer to reduce the effect or find another angle
  • Listed above as a benefit, slower shutter speed can also have a negative impact – higher ISO or slower shutter introducing blur
  • Reflected colour of objects or particles in the air (colourful sunsets) can disappear when using a circular polarising filter

Create the look using Adobe Lightroom Mobile app

If you are not in a position to purchase one of these amazing accessories - you can partially recreate the effect, using Adobe Lightroom Mobile app. 

 

Go to Adjustments > Effects > Dehaze and slide to the right. As always, my recommendation is to move the slider to where you like it - then move back, reducing the effect a little. This helps you, to avoid over-processessing your images. Even better, make you changes, go away for a littel while then return to review the image again!

Re-create teh polarizing filter look by using the Dehaze tool in Adobe Lightroom Mobile app

Summary

The circular polarising filter should be an essential part of your bag of smartphone photography accessories. There are a number of real benefits – especially when you understand when and how to use the lens.

 

As an advocate for mobile photo editing – there is no editing substitute for using a circular polarising filter at the time of capture. These really are magical and well worth the little investment to get yourself one of these units and take your smartphone photography to the next level.

Mike James hosts regular group workshops, workplace training and is a sought after speaker at photography clubs and social media training events. Get in touch with Mike here.

These articles are great to learn a mobile photography specific technique or tip. The fastest transition into the confident and creative smartphone photographer is this structured course 'Strategically edit WOW images on your smartphone'
 
The Smartphone Photography Club is where you can hang out with like-minded photographers. Club members take part in weekly photo themes in our closed Facebook group. You also get the full course, tutorials,  photo critiques and club sponsor discounts.