Neutral density filters are used to block some of the light coming into the lens so that we can have longer exposure times than the available light would allow without the filter. For landscape photography, neutral density filters are indispensable.
How Does a Neutral Density Filter Work?
To explain how a neutral density filter works, I used an old standby, the waterfall–shot on a bright and sunny day.
With the available light, we may have a fast shutter speed that will freeze every droplet in place. If that is what we want…great!
But what if we want that long and silky cotton candy effect we see so often?
To do that, we need to use a longer exposure time. That’s where the neutral density filter comes in. It blocks light entering the lens and allows for the longer exposure times needed.
Neutral density filters come in various densities and can be stacked to get to the exposure times we want.
If you live near the ocean, try going to the beach and shooting the waves as they crash onto the shore. With enough neutral density filters, you can smooth the water out and make it look like there were no waves at all! Toss in a dramatic sky, and you have a contest winner for sure!
In previous articles, I’ve written that the best time of day for landscape photography is at dawn and dusk. when we get the most beautiful light on our subjects. But there is a problem. Because of the dramatic difference in light (on the ground vs. in the sky) at that time of day, half your photograph is improperly exposed.
If our subject is the dramatic cloud formation in the sky, that’s great. We make the clouds the star. We expose for all the light in the sky, but that makes the ground go dark. (The ground is under exposed.)
If our subject is the ground, we expose for the minimal light on the ground, but that lets the sky get blown out. (The sky is over exposed.)
How can we shoot at the best times of day, still have a star in our photo–either the ground or the sky–but not have the rest of the photo be improperly exposed?
Split Neutral Density Filters
Enter the split neutral density filter (also called a “graduated neutral density filter”). This is a filter that is clear on one half and has a neutral density filter on the other half. These filters come in various degrees of density, and the division can be a sharp line or a gradual fade.
With a split neutral density filter, we can hold back some of the light in the sky and not affect the light on the ground. All we need to do is determine what the amount of difference there is in exposure value between the sky and the ground, then add enough neutral density light blockage to the sky to make the values equal.
Since the filtration is “neutral”, it will not take away any of the colors or drama in your shot… it just cuts back on the light being admitted into the lens.
Here is a helpful video tutorial on the subject:
“Getting lovely smooth water isn’t simply a matter of choosing a slow shutter speed. No, you’ll need to reduce the amount of light hitting the sensor by using a filter.”
Adding neutral density filters to your landscape photography arsenal is vital. You should never leave home without one if you want to put the “WOW” factor into your landscape photography.
About the Author:
Dan Eitreim writes for ontargetphototraining.com. He has been a professional photographer in Southern California for over 20 years. His philosophy is that learning photography is easy if you know a few tried and true strategies.
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