A circular polariser (CPL) blocks polarised light (light travelling in a single plane) from coming into your lens and is often one of the first filters a photographer will add to their equipment bag. In this quick post we will go through how to use a polarising filter and give you detailed information on what they do and why you should be looking to add one to your bag.
When to use a polarising filter
The main use for a polarising filter and the one which most people will initially purchase their polarising filter for is landscape photography. They’re great for cutting out unwanted reflected light and haze in a subject, creating a really crisp image which is rich in colour and contrast. The colour can be added to the image in post processing but reducing haze and reflections after the fact is almost impossible.
This is great for shooting objects such as water, as when light reflects off a non-metallic surface it becomes partially polarised and by adding a polarising filter you can cut this out and eliminate your reflections. This effect is most visible off still water, when the sun is between 30-60 degrees above the horizon, but can also be great when used on moving water, such as waterfalls.
Without polarising filter
With polarising filter
That’s not to say that a polarising filter should only be used for landscape photography, though. It’s a great tool to have in your bag for architecture and interior photography as well and can help eliminate unwanted glare on shiny surfaces and reduce the reflections in glass too.
They’re also great for product photography, such as bottles. Putting a polarising gel on your lights and using a polariser on your lens allows you to totally eradicate glare from the glass, a great time saving technique.
Your polarising filter won’t stop giving there, though. If you’ve ever taken a portrait of someone with glasses on and got a horrible reflection bouncing back at you, guess what? Your polarising filter can dramatically reduce that.
Here is a great video from American super store B & H which goes into great detail about how to use a polarising filter.
I think you can probably see that polarising filters have a multitude of uses for your photography and definitely have a place in most photographer’s kit bags. However, before you click “Buy It Now”, here are a few points to consider.
When not to use a polarising filter
It’s important to understand that just sticking a polarising filter on the front of your lens and turning it won’t result in a clearing image with amazing colour. Small details like the time of day and even the seasons will affect how your polarising filter will work, due to the quality of the light which is entering your lens.
The maximum degree of polarisation always occurs 90 degrees from the sun. You can find this by forming an L shape with your index finger and thumb, then pointing your index finger at the sun. The direction which your thumb points is going to give you the maximum degree of polarisation, making the sky appear even.
When the sun is directly above you and close to the zenith, i.e. in the summer months or at midday, the sky will be polarised horizontally. Towards the winter months or sunrise, the sky will be polarised vertically, which will give you an uneven polarisation and result in one side of the image going darker than the other.
A polarising filter can also produce a really unnatural looking sky when used at the wrong time or when over used and pointed at the maximum polarising effect, giving you a dark, almost black sky and a correctly exposed foreground. Here, you just need to rotate the filter to lessen its effect or simply remove it.
Polarising filters, by the nature that they cut out light waves, will reduce the amount of light hitting your sensor, usually by around 2-3 stops. So, you’re probably going to be needing to get that tripod out in order to use one.
Vignetting can also be a big problem when using a wide-angle. This can be handled slightly by not stacking filters or buying a slim polarising filter, but of course this is going to cost you a little bit more.
Best polarising filters
Most circular polarisers are designed to fit onto the screw-on filter thread on the front of your lens and then can be rotated to increase the effect of the polarisation.
The first thing to do is to check the filter thread size of the lens you are most likely to be using it on. Adapters or step-down rings are available for every thread size, to avoiding having to purchase multiple filters. The other option is to use a a square filter holder system. While a little more expensive at first, this will allow you to use the same filter across multiple lenses.
Lee is arguably the biggest, or at least best known manufacturer of filters for your camera and as such they demand a high price if you want to purchase their equipment.
They offer two separate designs of polarising filters as well as offering a slim option if you want to shoot really wide and avoid any vignetting. The first option is less expensive and fits directly into their 100mm square system. So if you already have the Lee Foundation Kit and want to build upon it this is a great route to take, although it does stop you stacking other filters as you will need to rotate the entire filter holder to get the polariser to work.
The second option is a stand alone 105mm filter which you will need to purchase a separate adapter in order to use. This sits on the front of your filter holder, allowing you to stack filters behind your polariser and still rotate your polariser.
Formatt-Hitech is another high end brand in the filter market and their filters are all made with high-quality Schott optical glass. Similar to the Lee system, they use a filter holder in order to mount the filters to the front of your lens. The benefit of this type of system is that you just have to buy separate adapters for the front of your lens and you can use all your filters on any lens you want, saving you from having to buy two or three of every filter if it is screwed directly to the lens.
The Format-Hitech system is a square system offering an aluminium 85mm and 100mm filter holder. The benefit of the 85mm filter holder is it can also fit the full range of Cokin P filters, which if you’re on a budget can provide a cheaper alternative for your less used filters.
Again, they offer a separate adapter to fit their 95mm polarising filter not their system, allowing you to use the same polarising filter across all your lenses.
In my experience, the Hitech filters do offer a slight purple colour cast when compared with the Lee filters, but this can be corrected fairly easily in post-production. The biggest drawback of the 85mm system is that it limits you to around a 20mm lens, so if you’re wanting to shoot ultra wide, go for the 100 system and get the optional wide angle adapter and you will have no issues on most wide angle lenses.
Hoya is traditionally more of a budget range (depending on how you view budget). It offers a number of screw-on filters which attach directly on the front of your lens.
The benefit of this is that they are far cheaper than buying a filter holder system, with the “pro” range coming in at around £50 per filter. The one drawback of this is that you can only use it on a lens which has the same filter size, so if you have multiple lenses, all with a different filter thread, you will soon need to buy multiple filters.