How to use a CPL filter (in)correctly

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Hoya 52mm CPL filter
One of my CPL filters.

Magic!!

That'southward what information technology tin seem like.

Nether the right circumstances.

Turning the ring of a CPL filter, looking through the viewfinder to see what happens.

Watching the glare from foliage disappear, the reflections from water being removed, or the heaven darken and the clouds and colors pop.

The situations are many, where the correct use of a CPL filter tin can seem to work like magic on the scene in front of yous.

Let's take a look at how to apply, and sometimes overuse, the polarizer result.

When to use a CPL filter?

A CPL, circular polarizing filter, or polarizer filter is a piece of drinking glass you attach to the front of a camera lens, which filters out certain parts of the light from inbound the lens.

The really geeky, nerdy, scientific explanation of how this type of filter works tin exist found here.

The CPL can be used for darkening skies, reducing reflections and glare from foliage, h2o, drinking glass and other reflective surfaces.

By doing this it will likewise in many cases raise the color saturation and contrast of a photograph.

Again, this in plow, tin can assist "cut through" or reduce haze by increasing the contrast in an image.

Some of these effects are difficult/impossible to do in editing software such every bit Adobe Photoshop.

That's why this is the most important filter you could add to your photographic armory.

An image of a waterfall illustrating the use of a cpl filter
This prototype illustrates how a circular polarizing filter tin can be used to remove reflection and glare from water surfaces.

Buy CPL filters here at Amazon.com

What'due south the rotating ring for?

This type of filter has an outer ring that rotates. With this band, you can "dial" in the desired strength of the polarizer result.

You'll find that often a subtle effect from the polarizer goes a long manner.

A trivial tip is ever rotating the ring clockwise, like when you spiral the filter ON the lens. Otherwise, you might accidentally unscrew the filter when y'all rotate the ring, and information technology might drop and suspension (yes of course it has happened to clumsy ol' me 😉 ).

A couple of things to consider when using a CPL filter

The bending of the lens relative to the direction of the sunlight

When using the filter for darkening the sky, you take to take into account where the dominicus is. If the sun is straight behind you, or in forepart of you lot, using the filter to darken the sky will have little to no effect. It doesn't affair how much you plow the ring.

At 90 degrees to the sun is where yous will get the virtually significant effect of the polarizing filter.

Knowing this, you'll have to be especially aware of the forcefulness of the event, when using a broad-bending lens.

The following image was taken with my Sigma x-20mm lens.

At 10mm, this lens has a 102-degree bending of view. This means that in mural shots similar this it will comprehend a smashing portion of the sky.

A mountain landscape with an undesirable polarizer effect
This mountain landscape shows how using a cpl filter excessively can lead to some undesirable effects in broad bending shots.

As you lot can see in this image, the right role of the sky is much darker than the left. This is due to what I described before.

The portion of the epitome that is ninety degrees to the sun is the darkest, and and then information technology tapers off to each side.

This is why you should take care when using a CPL filter with a wide-angle lens, or non use it at all, depending on the circumstances.

The filter steals some calorie-free

A standard polarizer steals about two-EV (aka f-stops) worth of light, pregnant you will have to compensate by using a longer shutter speed, raise the ISO or use a larger aperture compared to when non using the filter.

This may likewise exist used to your reward, for example if you lot need a little longer exposure fourth dimension to mistiness h2o. Then you'll have both the benefit of the longer exposure time AND the removal of the reflections.

Lens flare

Any additional piece of glass you stick in forepart of your lens volition make it more prone to lens flare. This concerns all filters, not only the polarizer.

Only be aware of it. Use your lens hood and/or shield the lens from the side with your baseball game cap or another suitable item.

A few things to consider when buying a CPL filter

Filter size

You lot'll have to know what size of filter that fits your lens. This is ordinarily printed in mm shut to the filter threads on your lens. Some mutual sizes are 49mm, 52mm, 55mm, 58mm, 72mm, 77mm, 86mm.

If you're buying a CPL filter for a super wide-angle lens like the Sigma 10-xx, it would be wise to get a so-chosen "slim" version. This filter is thinner than the regular filters to avoid vignetting (dark corners in the image).

Filter brands

A good filter is defined past the build quality of the rings and the quality of the glass. There is a jungle of brands out there, merely some of the more reputable ones are B+W, Hoya, Tiffen, Heliopan.