Photo filters are everywhere these days.On any smartphone or computer, there are dozens of apps and programs that will let you apply digital photo filters (from super- saturated to grungy to black-and- white to old-timey sepia) to change the look of your photo after you take it. But there is one filter that absolutely cannot be replicated after the moment of image capture. I’m talking about the polarizing filter.

As with polarized sunglasses, polarizingfiltersusedin photography work by selectively blocking light particles vibrating in a certain direction while allowing light particles vibrating in an opposite direction to pass through in a normal fashion. In easy terms, polarizing filters help to cut reflections on shiny surfaces and to deepen blue skies. Using a polarizing filter is key for many landscapes in Costa Rica as you’ll likely be including water, blue skies, and green foliage in many of your photographs.

A circular polarizing filter—which screws on to the front of your lens on more advanced cameras— will help you to capture all of the lushness that Costa Rica’s forests and beaches have to offer. Even when you’re in the forest and not including the sky in your photo, a polarizing filter will cut the reflections on wet and shiny rainforest leaves. Keep in mind that polarizing filters, which are made of dark glass, will cut some of the light hitting your sensor. You may need to raise your ISO level to keep your shutter speed up.

If you’re using a smartphone or a simple point-and-shoot camera that won’t take a polarizing filter, try shooting in HDR mode. This may help you to reduce some of the bright highlights in your photos.

Even though I was shooting from a rocking boat and worried about movement, I still deemed a polarizing filter essential for this photo of waves crashing against the forest coast in Costa Rica’s Gandoca-Manzanillo Wildlife Refuge.

A polarizing filter helped to saturate the blue sky and slow down the shutter speed for this midday shot of a beach in Cahuita National Park on Costa Rica’s Caribbean coast.