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Friday, September 1, 2006

Filters & The Landscape

Choose and use filters to improve and enhance your landscape photographs

Choose and use filters to improve and enhance your landscape photographsPolarizers
If you have only one filter, it should be the polarizer—the most useful of all filters. Though most people think of a polarizer for darkening skies or eliminating reflection, it does much more to improve contrast in a photograph.

Polarizers eliminate that annoying sheen and glare from vegetation, allowing the true colors to show. For this reason, I use polarizers in forests on overcast or rainy days. Polarizers can also cut out reflection from moisture in the atmosphere, reducing haze and therefore darkening the sky. If I need to reduce the exposure in the sky, I'll look to a polarizer first.

Polarizers reduce the light reaching the film or sensor by one to two stops, meaning an exposure adjustment is needed. Your camera's auto-exposure system will handle it, but be aware that the exposure will change. This change in exposure is sometimes an advantage if you need a longer shutter speed to blur water in a stream. Choose and use filters to improve and enhance your landscape photographsIn fact, I've stacked a polarize with a neutral-density (ND) filter to simply get longer shutter speeds. Be careful stacking filters, however, especially with wide-angle lenses, as you risk vignetting in the corners. Make sure to remove any other filter, such as a UV filter, as well.

A polarizer is most effective when the lens is 90 degrees to the sun. The impact of the filter is lessened or completely lost otherwise. I suggest that you not leave the filter attached to your lens. It's not worth the loss in light unless you're gaining the benefits of the polarizer.

The easy way to tell if a polarizer is going to have any effect is to hold it in front of you and rotate it. Make sure that you're facing the same direction as the camera and that the filter threads are facing you. If you like what you see, use the filter in that position on the camera.

Filters & The LandscapeGraduated ND Filters
Graduated ND filters work like half of an ND
filter—half of the filter is clear and the other is dark. Such filters can be used to control contrast in a landscape situation where the range of light is beyond the tonal capabilities of the film or sensor. They're typically used with a bright sky over a darker landscape. This high contrast makes it difficult to capture shadow and highlight details with a single exposure.

The grad filter balances the dark and bright areas, and brings them within the dynamic range of the film or sensor, enabling you to capture the full range of light in one shot.

Filters & The LandscapeFilters & The LandscapeFilters & The Landscape

Grad ND filters are available in different densities, normally up to four stops. They come with two different types of transitions: a gradual soft transition or an abrupt hard transition. Many landscape photographers prefer the soft-transition filter as it blends the area of change between the dark and clear portion of the filter for a more natural look.

ND Filters Filter Factors
ND 0.3 = 1 stop
ND 0.6 = 2 stops
ND 0.9 = 3 stops
ND 1.2 = 4 stops

Screw-mount filters force you to position the transition in the middle of the frame, which isn't always ideal for a landscape photograph. Instead, many photographers prefer rectangular filters that are held in front of the lens or slipped into a filter holder.

Filters & The Landscape  The Cokin "P" holders and adapters are widely available and inexpensive. I generally handhold my filters in front of the lens. This allows me to work fast in quickly changing light. Plus, I find it more convenient than attaching adapters and holders. This is easiest to do when shooting with a tripod.

Many wide-angle lenses have a filter diameter as large as 77mm, however, so it's important to use a large enough filter to cover the entire front element. Several manufacturers, including Singh-Ray, Lee and Tiffen, make filters that measure 4x6 inches, available with the usual densities and transitions. These oversized filters are easier to handhold. Plus, being so large, they give the photographer more creative options such as deliberately moving the filter up and down during an exposure to further' feather" the transition area.

Screw-In Or System?
Polarizing, neutral-density and graduated filters come in two basic types: screw-in and system. Circular screw-in filters screw into the threads on the front of the camera lens. The main advantage is simplicity: you don't need anything but the filter. The main drawback is that you have to buy a filter to fit each different-diameter lens you have or buy a filter to fit your largest-diameter lens, plus step-down rings to attach it to the smaller lenses. The better screw-in filters are made of multicoated optical glass. Popular brands include B+W, Heliopan, Hoya, Lee, Pro-Optic, Singh-Ray, Sunpak and Tiffen. Additionally,
most SLR manufacturers offer polarizing filters for their lenses.

Filter systems consist of a filter holder that mounts on the camera lens (adapter rings are used to fit the holder to different-diameter lenses) and rectangular filters that slip into the holder. The main advantages are that you can use the same filter with all your lenses; with most systems, there are slots for more than one filter so you can use combinations of filters—say,a polarizer and a graduated ND filter—simultaneously; and you can slide the filters up and down in their slots, so you can position the transition zone of a graduated
filter just where you want it. The main drawback to filter systems is that you have to buy and keep track of
the filters, the holder and the adapter rings. System filters are generally made of organic glass (high-tech plastic). Popular brands include Cokin, Hitech and Lee.

To determine what strength of filter you need, it's best to take a meter reading of the highlight, then the shadows, and note the difference in exposure. Using too strong of a filter can result in the highlights being darkened too much and thereby a loss of detail.

Though some photographers forego the use of grad filters and opt for making two or more exposures of a scene and blending them together in Photoshop, using a grad filter takes a fraction of the time that would be spent achieving similar results on the computer.

Landscape Filters Chart PDF

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