IntroductionOne of the most common situations that the outdoor photographer runs into is variance in lighting that exceeds the dynamic range of the film or sensor (think of dynamic range as the ability of the film or sensor to capture both the lighter and darker elements of the picture). Often you’re in the situation where you feel that you have to give up one part of the photograph or another. This is especially true in situations where the sky is much brighter than the land, or where strong shadows exist within parts of the photo. And, with the popularization of digital cameras, this is even more critical, since digital cameras are generally considered to have about one f-stop less of dynamic range than film (making this a strong plus for the continued use of film in certain situations). A very noticeable symptom of this loss of dynamic range for the outdoor digital photographer is the loss of delicate texturing in clouds, giving them a “cartoonish” look. But, regardless of whether you shoot film or digital, the GD filter offers you the opportunity to better control certain lighting challenges.
The Graduated Density Filter
The reader should see immediately the usefulness of these filters! Consider the image at the near-right.
This proved to be a perfect opportunity to use a graduated density filter. At this point, a more technical photographer might wish to meter (using a spot meter) both the lighter and darker elements of the scene, and then select the required filter density based on those results. However, in this case the photographer (Mark Doiron), used his “calibrated” eyeball and guessed that the GD2 (Graduated Density, 2 f-stop) filter would be the right match. You can see the result at the far-right, which was shot at 1/50 second and f/5.
Hard and Soft Edge Graduated Neutral Density (GND) Filters
Reverse Graduated Neutral Density Filters
Creative Use of Graduated Density Filters
For those who are willing to take more “artful” measures with their photographs, the GD filters provide the opportunity to darken portions of an image to achieve special affects. That was the technique used on this image of the Crestones (left) to create a dark, foreboding sky with a GD2 filter. However, unlike in the image of the pond, where the filter was set essentially to allow the middle of the filter to cross the middle of the frame, the photographer chose to slide the filter up within its holder, thus darkening only the very top of the image. This is possible with a GD filter because, unlike filters that attach directly to the threads on the lens, the GD filter requires a special mount that attaches to the lens, then the filter slides into that mount. When mounted, GD filters have the ability to slide up and down (or side to side), rotate freely, and be stacked into the holder (usually a maximum of two).
As briefly mentioned before, GD filters are also available in various colors to artificially enhance (or even create!) the appearance of sunsets, alpenglow, fog, blue skies, or even unnatural colors.
One thing worth noting about these uses of GD filters: While most photographers willingly accept the use of a neutral density GD filter to better balance light to achieve a more natural appearance in the final image, some draw the line at creative uses such as the one at the left, or anything that changes the colors beyond what the photographer witnessed. The authors encourage anyone using these techniques to be forthright when asked about their work.
This brings up the subject of hardware. That is, as previously mentioned, GD filters require special mounts. Here’s what is required using the Cokin™ filter system (see figure at right):
o Filter screw adapters (adapt the filter holder to various size lenses you own)
o Filter holder, single filter (holds only one filter, but has minimum vignetting) or two filter (holds two filters, but might vignette with wide lenses. Useful for stacking GD filters when extreme difference in lighting levels exists)
o GD filters, +1 and +2 (both recommended)
o Lens shade (optional, but your standard lens shade won’t fit. You might find your hat useful, though!)
o Lens cover (optional, but protects lens when filter holder is installed. Not shown in figure)
One last point: The Cokin™ filters come in three sizes: A, P and X-pro (see figure at left). This is the size of the filter itself, not to be confused with the adapter rings for your lens collection. You need to select a filter size that will accommodate the lenses you use. If you don’t ever use really wide-angle lenses, then the inexpensive, but rather small, A-series filters may suit your needs. Generally, the P-series filters have minimal vignetting with most SLR camera lenses, while being reasonably priced and practical to carry while hiking.