When Should You Use A CPL Filter in Landscape Photography?

CPL Filters (Circular Polarizers) is a filter that reduces reflections/glares, haze, and darkens blue skies.

CPL Filter by Lee Filters

The filter reduces or controls the amount of light that reaches your camera lens. The filter can enrich an image making it clearer and more vivid, but for maximum polarization to occur, you have to be 90 degrees from the sun or the source of light.

What instances would you use it in? I would use to reduce reflections in the water so that I could see through to the rocks to reduce the shine on leaves, and if I were photographing a cityscape, I would use it to get rid of the glare in the windows. This filter sounds fantastic, right? Why would you ever take it off? Well, it can also harm an image. CPL filters can actually filter out an entire rainbow or other rays of light; they can turn people's faces red, and they can make your image weird looking (dark on one side very light on the other) when you are not at the right angle.

Always look at your subject matter first, then determine if the situation calls for the filter to be used. You always want to think about the subject matter first, then think about how to execute it.