Lens filters, especially circular polarizing (CPL) filters, may not feel like a necessity in the digital camera world, but they are ever so useful in the right circumstances. Polarizing filters are so named not because they polarize opinions on there usefulness, but due to their unique way of balancing light entering the lens.
What Are CPL Filters?
Most polarizing filters we use today are circular, which basically means there is firstly a linear polarizer on the front of each filter, with a quarter-wave plate to convert to circular polarized light, which works more efficiently with modern autofocus systems. It’s possible to use a linearly-polarized filter on its own, but some image sensors which use a low pass filter or anti-aliasing filter may not work as well.
Coupling two types of polarizing filters together means the filter can be turned to create different levels of effect. You can also tell a CPL filter from a linear polarizing filter as the effects can only be viewed when looking through the back of a CPL filter. If you want to dig into the full technicalities of how CPL filters work, this is really its own separate, full topic. But as photographers, we are often more interested in the applications and usefulness, with maybe a dab of technicality here and there to back up the claims.
Which begs the question, how can we use a CPL filter in the wild?
Using CPL Filters
All non-metallic objects can reflect light, which can be polarized, providing unwanted glare and reflections. A CPL filter essentially absorbs all the unwanted light and can be rotated to adjust the effect. This means reflections from shiny surfaces such as water, glass, and glistening skin can be vastly reduced, at the same time enhancing the natural color and definition of an object.
CPL filters are a favorite of landscape photographers as they can filter out polarized light from a bright sky, bringing out the colors, while also bringing out more definition in clouds and the landscape. While it’s completely possible to darken areas of an image in post-editing, the full light polarization isn’t recorded at the time of exposure, which means it’s down to a CPL filter to get the job done right.
One caveat of a CPL filter is that less light is let through to the sensor by up to a few stops, which means exposure settings will need to be changed to either slow the shutter speed, increase ISO, or increase the aperture. A similar effect can be achieved with neutral density filters, which use two linear polarizing layers, but don’t have the variable adjustment, meaning you will need a bunch of them to get the correct effect for a certain scene.
There are other dependencies for producing the best results from CPL filters, such as having your subject at a 90 degree angle to the sun’s direction. But in reality, there is no substitute for practice, shooting with and without the filter, and varying the adjustments for each scene. Which brings us nicely onto recommendations for the best CPL filters. There are plenty of options on the market, but we will focus on the more respected brands which will ensure quality and long life.
HOYA is another respected filter brand, and the FUSION ONE CIR-PL is one of its best. The FUSION line brings high-quality glass and 18 layers of Super HMC multi-coating for better light transmission and reduction of flaring and ghosting. The surface of the filter is also stain-resistant and water-repellent.
The filter itself is low-profile and while it’s not the thinnest example around, it can still fit nicely on a wide-angle lens without any trouble. Optically, the filter produces a fine reduction of reflections, with only an extra half stop of compensation required over other top end CPL filters. The HOYA FUSION ONE CIR-PL is also reasonably priced considering its level of quality, with easy gripping on the outer rim and lots of thread sizes to choose from.
The B+W XS-Pro Kaesemann HTC CPL MRC Nano Filter strikes a nice balance between price and features, coming in a wide range of thread diameters. The thickness on this filter is 4.5mm, which isn’t the slimmest one on the market, but this feature also makes it easier to grip and rotate.
There is roughly one stop of compensation needed when using this filter, but the most important factor is sharpness stays on point, with no color casts. The results are generally very good with the B+W XS-Pro, but the MRC Nano coating isn’t always the best at repelling water or fingerprints, which is really the only letdown with this example.
For a real budget solution, you can’t do better than the Tiffen Circular Polarizer. This example is the cheapest CPL filter on this list and while it produces respectable results, the overall quality is not as good as the Hama below. The Tiffen falls short representing certain wavelengths and you will need to experiment with your white balance settings to get the best results.
The filter also adds a small amount of saturation to images, which can be a good thing, but it can also show some vignetting on wide-angle lenses. Basically, if this is your first foray into CPL filters, then the Tiffen is a good first port of call.
5. Hama Polarizing Filter (Budget Winner)
The Hama Polarizing Filter is for those who want a cost-effective solution, without a large price tag. Coming in a wide range of filter sizes, the circular filter has an anti-reflective (AR) coating for increased light transmission, with roughly a 1 1/4 stops of compensation needed.
The filter does a good job of clearing up reflections, with only the tiniest drop in image sharpness. It’s also 6mm thick, which means it may not be the greatest application on very wide-angle lenses, but at least it has features such as a removable side pin to more easily turn the filter. It’s also not the best at stopping fingerprints on its surface, but as an all-round cost-effective solution, the Hama Polarizing Filter provides good optics for the price.
Summary of the Best CPL Filters
As with any glass that you attach to the front of your lens, it’s always wise to invest in the best quality lens filters possible. Saying that, there are plenty of CPL filters available at different price points, but there’s nothing like high-quality glass to produce the best results.
For photographers out there who always have a hard time reining in unruly reflections and glare, why not give a CPL filter a test drive?