Using the Graduated Density (GD) Filter to Control Lighting in Outdoor Photography

Introduction

One 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

Basically, the GD filter is half clear and half tinted. In the middle it gradually fades between the clear portion and the tinted portion (See figure at left). The tinting may be in various shades of color, but for the outdoor photographer trying to remain true to the scene (e.g., not trying to create heavily colored alpenglow where it didn’t exist), the neutral density (neutral gray in color) filter is a versatile tool. These filters are generally available in either one or two f-stops (that is, the tinted portion of the filter reduces light by either one or two f-stops as compared to the untinted portion, which doesn’t affect the light).

The reader should see immediately the usefulness of these filters! Consider the image at the near-right. It was shot using a Canon EOS 30D at 1/100 second, f/7.1. Exposure compensation was set to 0. The sky is a very light blue, much lighter than optimum. The trees reflected in the pond are much too dark. The photograph lacks the impact that a more balanced scene would provide.

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. Slowing down the shutter and opening up the lens (depth of field wasn’t a factor at such a short focal length) allowed more light to brighten the darker parts of the first attempt (these parts were behind the clear part of the GD filter). And the GD filter reduced the light coming from the upper portion of the image (which was tinted). The result was a well-balanced image that better presented what the photographer was seeing (the human eye being much better at adapting to diverse lighting in real life than on a photograph).

Hard and Soft Edge Graduated Neutral Density (GND) Filters

Singh-Ray™ GND filters come in either a soft-edge or hard-edge form. The soft edge provides a more gradual transition between the dark and light portion of the filter and is useful where the subject has bright and dark areas that mingle. In contrast, the hard edge has a sharper, better defined transition. The photo at left was taken using a 3-stop hard-edged GND filter because the boundary between light and dark areas of the subject was both straight and well-defined.

The reverse Graduated Neutral Density (GND) filter. Notice how it gets lighter at the top.

Reverse Graduated Neutral Density Filters

The 2 and 3 stop reverse GND filter can be very useful when there is a dark foreground with a bright horizon and dark clouds above the bright horizon. This condition is common during cloudy sunsets or sunrises.

Creative use of a GD filter.

Unlike regular GND filters that are dark in the middle and tend to get darker above, reverse GND filters are dark in the middle then get lighter above.

To the left is an example where using a 3-stop reverse GND was appropriate. Using a regular GND filter would have resulted in a properly exposed foreground but because the top part of a regular GND filter is dark, the naturally dark clouds would have been underexposed. Instead, because the reverse GND filter is less dark on top, the clouds’ exposure more closely resembles reality.

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.

Hardware Requirements

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):
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Available filter sizes.

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   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.

Conclusion

Graduated density filters provide the opportunity to better present the sights you see. They're an indispensable tool for the digital, outdoor photographer, and are useful even for died-in-the-wool film buffs. When used properly, they have the potential to take your photography to the next level.

Images

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