Following on from the previous post on Fall photography tips, here are three filters that can help you take better Fall photos. You don't need any filters to take great Fall photos, but these filters can help you enhance reflections and color, and give moving water a silky look.
A polarizing filter can be particularly helpful for fall photography. It can be used for reducing reflections from leaves, enhancing the color saturation. It can also be used for removing reflections from water, useful when you want a photo of brightly colored leaves floating in a dark river or lake.
Alternatively, a polarizer can be used for increasing reflections, helpful when capturing the reflections of trees in water.
Another use for a polarizing filter is to enhance and deepen the blues of a blue sky. Fall foliage, particularly yellows, contrast strongly against a blue sky, making them pop out more.
A specialist filter, useful mainly just in Fall, is the Redhancer filter. This filter, also known as a Didymium filter, has an effect of increasing the saturation of red colors. Used when capturing subjects with orange, red, and brown colors, it can really make the colors pop.
If you use a redhancer filter during the middle of the day, you may find that it introduces a magenta cast to objects that should have a neutral color (e.g. clouds). It works best when the color temperature is warmer e.g. early morning, late afternoon, as the light contains more red at this time of day.
Neutral density filter
A neutral density filter reduces the amount of light your camera receives, allowing for longer shutter speeds. With your camera mounted on a tripod, a long shutter speed will allow you to blur moving water, such as rivers and waterfalls.
On a windy day a slow shutter speed can be used for abstract photos of blurred fall foliage blowing in the wind. If you hand-hold the camera you can create some nice abstract photos by moving the camera up and down in a direction parallel to the tree trunks.
You'll end up with a photo full of streaked fall color permeated by white or brown lines of just about recognizable tree trunks. Try other movements as well for different effects. For example, moving the camera in a circular pattern makes for a nice swirly effect.
On cloudy days when there isn't much light, you might find it is dim enough that you can use a long shutter speed without a neutral density filter. This is particularly true for late afternoon or early morning when there is less light anyway.