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Essential Filters

Although for some people programs such as Adobe Photoshop have reduced the need for filters (say farewell to the trusty old starburst filter!), there are still some filters that we regard as being essential items in a well-stocked camera bag. Others that we'll mention here may not be totally essential, but they help modify the light in specific ways and let you create images that would be difficult or impossible without them. Not all digital cameras can accept filters and some can only use proprietary filters designed by the manufacturer. To accept standard screw-on filters, the front of the lens will have to have a threaded ring. If your lens has this feature, then there should be a number indicating the size of the filter that will fit on the lens. Here are filters to consider:

  • Skylight and UV filters. These filters are clear glass and are mainly used as protective covers for the lens. The idea behind this is that if there is an impact to the front of the lens, or contact with a scratchy item such as a bramble bush, the filter will take the brunt of the punishment and spare the front glass lens element from being damaged. We suspect that there's also a certain amount of add-on selling here by camera shops and online dealers, but the basic premise makes sense and we use them as lens protection. A $20 to $40 filter is less painful to write off than an expensive lens costing hundreds of dollars. UV filters can also help to cut down on atmospheric haze to yield a clearer shot.

  • Polarizing filter. Of all the filters that we carry in our camera bags, we'd have to say that a polarizer is the one filter we just wouldn't want to be without. Like all filters, a polarizer modifies the light as it enters the lens. Chief among these modifications is a polarizer's ability to remove some of the glare and reflections from the surface of glass and water. It also excels at darkening blue skies and boosting color contrast and saturation. The quality of light in a scene can be made clearer and less hazy. The amount of polarizing effect you get will depend on a few variables, including the time of day, the angle of the light relative to the scene you are photographing, and the reflective properties of a given surface (Figure 5.27).

    Figure 5.27. A polarizing filter can dramatically improve landscape images by reducing glare on water, darkening a blue sky, and increasing color saturation. On the left, a high-country lake with no filter; and on the right the same scene improved with a circular polarizer.

    The best type of polarizing filter to use on an autofocus SLR camera is a circular polarizer. Don't use a linear polarizer with an SLR, because it can confuse the camera's autofocus and metering systems. A circular polarizer allows you to rotate a circular ring on the front of the filter and adjust the level of polarizing effect until you get it just right. Polarizers are darker filters that will cut down on the amount of light entering the lens and this usually means using a wider aperture or a slower shutter speed. Since they reduce the light entering the lens, they are easiest to use on cameras that use TTL metering (through the lens) so you don't have to calculate a compensating adjustment. For rangefinder cameras (see Chapter 4, “Buying a Digital Camera”) that also feature an LCD screen that shows you a live preview of what the lens sees, circular polarizers can be used in much the same way as you would with an SLR, by rotating the ring until the effect looks best. The only drawback is that these screens can be somewhat hard to see in bright light, which makes it more difficult to evaluate the polarizing effect. Seán has been able to use his larger circular polarizing filter on a Nikon Coolpix 5400 by simply holding it against the front of the lens (Figure 5.28). Since the preview on the LCD is sometimes hard to see, to judge which rotational angle is best, he first holds the filter up to his eye and turns it until the effect looks good. Then he places it in front of the lens, making sure to keep the filter rotation the same. Fortunately, his Tiffen (www.tiffen.com) circular polarizer has a small handle for turning the ring that makes it easy to use as a positioning marker.

    Figure 5.28. On non-SLR digital cameras, the polarizing effect can sometimes be hard to see on the LCD screen. It helps to hold the filter up to your eye first, to establish the correct rotation position, and then take note of that and mount it on the camera, or simply hold it tight against the lens, as we did here for the shot on the right, taken with a Nikon Coolpix 5400.

    If you're using a polarizer on a rangefinder camera that does not also have an LCD screen showing what the lens is seeing, then you won't be able to see when the polarizing effect is best, so your success will be somewhat hit or miss. For this type of camera, especially if it does not use TTL light metering, a linear polarizer is best. You'll also need to factor in a plus-1 or plus-2 stop exposure compensation to adjust for the darker filter letting less light through the lens.

    Few things liven up an outdoor shot like a polarizing filter. Although you can use Photoshop to darken a blue sky and add some saturation into the colors of an image, it doesn't replace a good polarizing filter. We regard this one as a must-have accessory.

  • Neutral density filters. These filters reduce the amount of light that enters the lens. Since they are neutral, they do not affect the color balance of a scene. Neutral density (ND) filters are used for times when you want to achieve a certain effect, such as shallow depth of field produced by a wide open aperture, or a motion blur from a slow shutter speed, but the lighting conditions are too bright to allow the necessary settings. Flowing water is a classic subject for a slow shutter speed treatment, as is long grass blowing in the wind. By placing a dark ND filter on the lens, you cut down on the amount of light, making the wider apertures and slower shutter speeds accessible (Figure 5.29). ND filters are commonly available in 1-, 2-, and 3-stop increments, and darker ND filters can also be ordered that will cut back as much as 5 stops of light (Figure 5.30). For times when you need a really strong ND filter, you can stack them together to increase the darkening effect.

    Figure 5.29. Even though this image was made on a brightly lit day, by using a tripod and a special neutral density filter that cut back 5 stops of light from entering the lens, Seán was able to use a very slow shutter speed of 20 seconds to render the rushing water as a silky blur.

    Figure 5.30. A Singh-Ray 5-stop Neutral Density filter shown in a Cokin P-series filter holder, and a Tiffen ND 0.9 filter that cuts back 3 stops of light.

  • Graduated neutral density filters. Graduated ND filters are dark on the top half and then gradually fade to transparent along the middle of the filter. They are used in situations where the sky area of a landscape shot is much brighter than the terra firma below the horizon. By using the filter to darken the sky, a more balanced exposure can be made for both the earth and sky portions of the image. Standard graduated ND filters that screw onto the front of the lens are less than ideal since you can't adjust the placement of the horizon line; it's always right through the middle of the filter. A better approach is offered by Singh-Ray (www.singh-ray.com) with their Galen Rowell Graduated ND filters. Designed by the late, renowned nature photographer, these filters come in a range of densities and also feature either a hard-edged or soft-edged gradient transition from dark to transparent. Since the filter is a rectangular piece of acrylic that fits into a standard Cokin P-series filter holder, the photographer can adjust the graduated edge of the filter up or down to match the location of the horizon in the image. This makes them ideal for compositions where the horizon line is not centered (Figure 5.31).

    Figure 5.31. (Images A & B) A graduated ND filter can help to hold back the light of a bright sky and create a more balanced exposure, as shown in the second image. (Image C) Galen Rowell 2-stop graduated ND filters with hard and soft transition edges, from Singh-Ray.




    The advent of digital cameras has introduced a new way of achieving this effect that involves shooting two (or more) exposures on a tripod, with each one exposed for a specific area in the image. In the digital darkroom, these exposures will line up perfectly (if the f stop is constant) and the best parts of each one can be used in the final image to create the balanced exposure that was not possible to capture in the field. Still, it does require some skill with Photoshop to do this well, and for those who haven't reached that part of the learning curve, or simply prefer to do as much as possible in the camera and on location, then graduated ND filters are an elegant solution to a common photographic problem. We'll cover the layered multiple exposure method in Chapter 11, “Digital Darkroom Expert Techniques.”



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