Tech Notes from the Field: Using Filters for Photography

Neutral Density Filters

During our National Park Photography Master Class and First Horizons workshops, we are often using filters for photography- specifically neutral density (ND) filters. To be clear, these are full neutral density filters, not gradients which are sometimes used to darken landscape skies.

Fixed vs. Variable

using filters for photography
Neutral Density Filter in use

There are two types of ND filters, fixed and variable, and you can buy them as screw-on filters for your lens or with a lens holder that mounts in front of your lens. (Here are some examples: Variable Filter, Fixed Filter) I use both, but I find that the fixed is more precise than the variable. With some practice, a well-made variable can render excellent results as well.

silky smooth waterfall with neutral density filter
Neutral Density filter used to get a silky-smooth waterfall. Photograph by Dennis Oliver, Lassen National Park Workshop

The issue with variables is that because you as the operator are turning the vari ring on the filter it can be difficult to achieve a precise setting. At some settings, you can develop an exposure artifact that looks like an imprecise vignette or create a dark X in the middle of the image.

The fixed neutral density filter evenly blocks some of the light so you can reduce the light during the day and create a longer exposure duration, which is very handy for waterfall images and skies in some cases. Fixed ND filters have a specific density, so you can quickly adjust your exposure settings based on adding the ND filter to the mix.

The variable neutral density filter is a different horse altogether because it is made from two polarizing filters, one stacked on the other. The rotation of the two filters relative to each other provides the variable amount of light-blocking capability, and while there are marks on the outer ring, these are not calibrated adjustments. As we know from using a single polarizing filter, we can introduce an X effect into an image at some settings, and this will occur with a variable as well.

Which One Should You Use?

I use and teach our workshop participants to use both. The variable is flexible but requires more careful application whereas the fixed units have no challenges. Variables have a range of 2 to 10 stops and fixed come in ranges of 2, 4, 6, and 8. With a filter holder, you can stack your fixed ND’s to achieve other combinations of neutral density.

ND filters are a useful creative tool, and every landscape photographer should have them in their camera backpack.

About Author

Bob Killen is a nationally recognized Fine Art Photographer, Landscape Photography instructor, and artist. He is the Director of the National Park Photography Expeditions, President of the Mojave National Preserve Artists Foundation, a National Park Service Friends Group, a national speaker on landscape photography and an Adobe Certified Instructor. His thematic work explores Western Americana landscapes with a focus on man’s obsession to abandon structures, places, and things across a shared American landscape. His work is owned by collectors in 20 countries.

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    […] National Parks, along with sharing photography tips and product reviews. Their latest blog entry, Tech Notes From the Field: Using Filters for Photography, explores the two kinds of ND filters: fixed and […]

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