Filters for Landscape Photography: Circular Polariser (CPL)
The circular polariser (CPL) is probably the most important filter in every landscape photographer’s bag. This essential piece of glass filters out the polarised component of the light in your scene, thus enhancing contrast and details. It basically functions as your camera’s sunglasses in almost every situation (and yes, your camera will definitely look cooler with that on as you can see from the picture here). This filter needs to rotate to a certain angle in order to engage its polarising effect, depending on the light of the scene you are about to capture. I personally use the circular polariser 90% of the time and it is the first thing I put on my camera after the shutter release. Especially if you shoot a lot of seascapes scene, the CPL should always be glued to your lens (figuratively, not literally). I am a polariser addict, I know, but there's no shame in that.
As I was saying, the CPL is very useful in landscape photography since it cuts out the polarised light. Cool, but what does it really mean? It means that this filter will absorb most of the reflected light and improve the lighting, saturation and contrast of your scene. To sum up, the polariser darkens the sky, increases the micro-contrast, saturates the colours and removes glares from body of water and wet surfaces. Sounds great, right?! That’s why I am addicted to it. For example, in the image below you can see the difference between the straight-out-of-the-camera RAW file with and without the polarising effect. It is quite an impressive and very pleasant effect.
How to use the CPL
By now you should be pretty excited to buy and try the CPL for your first time. The question is: when and how should you use the polariser? Well, it is very simple. Screw the CPL onto your lens or in your filter holder, spin it and see what effect it casts on your scene. Usually, the maximum polarising effect happens when the light of the sun is at 90° degrees (or perpendicular) from your lens, like the picture of Mt.Cook above. Be careful though to dose well the polarising effect as sometimes it may look unnatural and darken the shadows too much or leave a big "blob" in the sky, especially when using an ultra-wide-angle lens. In the straight out of camera RAW file below, I wasn't careful enough when spinning my CPL and the result is that big dark "blob" in the upper right corner of the sky. Needless to say, it does look unnatural and fixing this problem in LR or PS is definitely a pain in the tushies. In the RAW file on the right instead, I have tuned my CPL in a good way, removing the glare from the wet rocks in the foreground in a natural way and preserving my shadows too.
A common situation where the CPL is essential is when you are photographing reflecting lakes. In this case, the polarising effect removes the glare caused by the water surface, enhancing the details of the reflection. This kind of glare is also present on wet surfaces such as rocks and plants, therefore a CPL is absolutely essential when shooting waterfalls, rivers, streams or waves. Basically, the circular polariser is almost always useful to bring your landscape photos to the next level. For this picture on the left, I have used and tuned the CPL to cut off most of the glare from the lake. The result was a nice frame with a very detailed reflection. It also partly darkened the sky on the top right corner in a natural way as I was shooting almost 90° degrees from the sun and I was careful enough when spinning the filter. In this other picture below, I also used the CPL to remove the glare from the water and from the wet rocks in the foreground, in order to achieve a more pleasant look for my shot.
Although the CPL effects are very useful for landscape photography, there is a teeny tiny trade-off. As I mentioned above, the polariser functions as your camera’s sunglasses and is consequently a dark piece of glass, which subtracts 1 to 2 stops to your normal exposure. When on a tripod, this shouldn’t bother you too much, but you must be careful when shooting handheld, since the use of a CPL could underexpose your shots and lead to slower shutter speeds. This trade-off can be either a blessing or a curse. When I visited the world-famous Moeraki boulders in NZ, I have used the CPL to get rid of the glare from the sand and this slowed my shutter speed just enough to reach that 0.5s to 1/5s sweet spot for photographing the waves, I then kept playing with my aperture and ISO settings as the light was changing. You probably already figure out that this effect can also be a small problem when shooting water motion in low light conditions, since it may slow down your shutter speed far from that sweet spot. But you are a jedi master of the exposure triangle and the histogram now, so you know what to do.
When NOT to use the CPL
We can all agree now that the CPL is awesome, but there are also some situations when you shouldn’t use this filter. Rainbows, for example, are amazing natural phenomena and they are the result of dispersion, refraction and REFLECTION of light in water droplets. Hence, rainbows are, by definition, polarised light. When in presence of a rainbow, the polarising effect of your CPL will remove it from the scene. Take as an example this snapshot of the Victoria Falls. I was struggling to shoot these fantastic waterfalls, when the sun poked through the clouds behind me creating a beautiful rainbow. At that time, I was using my CPL, but I had to dis-engage its polarising effect in order to capture the rainbow. Needless to say, I could have taken a better shot, but believe me when I say the conditions next to this massive waterfall are everything but easy. Another situation where the use of the CPL is not recommended is when shooting sunstar pictures (aka shooting directly into the sun). In this case, there won’t be any polarising effect as you are shooting directly into the sun; therefore, your CPL is useless. You shouldn’t have any filters at all for this kind of photography to avoid those big and colourful filter flares. Unless you like those big and colourful filter flares.
Last but not the least, the CPL is not recommended when shooting panoramas as well. When you shoot a panorama, you’re panning your camera from left to right or vice versa, taking in a bigger scene and changing the position of the lens from the sun. This variation is such that the polarising effect will change throughout the scene, leaving a big dark “blob” in the sky. Always remove or dis-engage your CPL when shooting panoramas; you will then avoid a lot of pain in post-processing to correct that dark spot. The RAW file of the panorama below shows you what happens when you forget the CPL engaged during your panorama series. I really had big plans for this panorama as I wanted to print it super large, but the "blob" here is too strong and I couldn't correct in PS (DAMMIT!!!).
To wrap it up, the CPL is definitely the must-have filter for every landscape photographer. This filter can be a “screw-on” version to screw directly onto you lens or a circular filter for your square filter system. Screw the CPL on, spin it and see what kind of effect it casts on your picture. This polarising effect cannot be reproduced in post-processing and it is super useful to darken the sky, increase the contrast, enhance saturation and remove glares from wet surfaces. Make sure that the effect is not too strong to cause any noticeable dark spot in the sky, otherwise you’ll end up with a ginormous "blob" in your frame.
From a great polarising effect comes great responsibilities, folks.