Filters are to photographers what adjectives are to writers. They help inject color and a personal style to what is being communicated.
Photography is a great medium for the communication of ideas and visions. Unfortunately, this medium's translator (film) isn't. The problem is film does not see the same way we see. Our eyes, emotions and imagination can perceive and enjoy a warm colorful sunrise over a foreground field of dew laden wildflowers. Film on the other hand has no emotions or imagination and only sees light as levels of brightness. This scene that may move us emotionally, is only a narrow series of bright and dark light values to film. "Narrow" being the key word here. Film (for this example, color slide film) can see a contrast range between light and dark of about 3 to 4 stops maximum. Or the other hand, our eyes can perceive a contrast range in excess of 10 stops. In this example the dawn sky could easily be over 5 stops brighter than the foreground of wildflowers.
This large difference in brightness between the sky and foreground is beyond film's ability to see and record. Regardless of the metering system you have in your camera or employ manually, you cannot capture that image or film . . . without a little creative help.
That help comes in the form of a filter. To be more specific, a Graduated Neutral Density Filter. These filters help reduce and balance the contrast range in a scene to a level that then can be recorded on film. These filters come in varying densities and rates of transition, clear at bottom with varying percentages of neutral density starting at the middle and increasing in density toward the filter's top.
If you are unfamiliar with graduated filters and their use, I suggest reading the information sheet written by Galen Rowell, or contacting Bob at Singh-Ray for any technical assistance at 1-800-486-5501
Like any tool however, standard graduated filters do not work their magic in every situation. One problem I continually ran into was shooting into the direction of the sun right at sunrise or sunset. In this application you have a dark or backlit foreground coupled with an extremely bright horizon. All graduated filters regardless of density or rate of transition go from lighter to darker in density, which is actually the reverse of what's needed in this case. A seemingly simple solution would be to physically turn the filter upside down and position the top edge of the filter over your lens parallel with the horizon. Unfortunately, regardless of lens or aperture used, the filter's physical edge bends, reflects or distorts the incoming light. This leaves an unwelcome bard of light or distortion on the image.
The solution to this problem came in a phone call to Bob Singh. With an explanation of the problem and a little experimentation we developed some filters, that, like all graduated filters, were clear at the bottom, however at their horizontal middle started very abruptly with either a 1, 2 or 3 stops of neutral density and then graduate to 1 or 2 stops towards the top of the filter. These three reverse graduated filters have solved many tough lighting situations. Used either separately or in combination with one another, depending upon the scene. I've been able to capture many unique images that before now were beyond my equipment's ability to record.
Say you've chosen a composition of shooting east into the sunrise with a field of wildflowers as your foreground. First meter the foreground and then the sky just above the horizon in your composition. In this example let's say the exposure difference between the two areas is 4 stops. Using the depth of field preview control (see tips), position a 3 stop reverse graduated filter over your lens putting the abrupt edge of the neutral density level with the horizon. By now exposing correctly for the foreground, the sky will only be overexposed for approximately 1 stop (well within the exposure latitude of any film). It's been my experience that slightly overexposing the sky will generally yield a more realistic-looking final image, if that's your intent. If you too closely balance the sky and foreground exposures, an unrealistic image will "usually" be the result. I emphasize "usually," as I am sure you're all aware this is photography we are talking about, not rocket science, there are no rules or formulas. Let experimentation, creativity and personal taste guide your use of these tools.
This example is common in terms of exposure difference between sky and foreground and if you can only afford one of these filters, I would recommend starting with the 3 stop reverse graduated filter.
Tips and Advantages
The image area being filtered will change according to your aperture setting, with the smaller apertures yielding a greater percentage of area covered by the filter. However, this is not visible when viewed through your lens if it's wide open. Use the depth of field preview control you (hopefully) have on your camera. This will better help you to visualize and position the filter for its desired effect.
These filters work best with flat or regular horizon lines. Any subject passing from the foreground through the horizon into the sky will also end up being filtered. If that subject is in silhouette however, this will not be a problem.
Wide angle lenses, because of their inherent greater depth of field (particularly with smaller apertures), will deliver a more pronounced and noticeable graduation than longer (50mm and up) focal lengths. My personal preference, however is with lenses in the 17 to 28mm range.
All of Singh-Ray's graduated filters are physically longer than they are wide. This advantage allows you more control over how much or how little graduation you want to use without worrying about the filter's top or bottom edge vignetting into the image. I use the Cokin "P" size filter holder which works well with all the lenses I use. Your personal choice will not be a problem as Singh-Ray can custom make the filters to fit ANY holder or lens (call for details and pricing).
As the name suggests, all Singh-Ray neutral density filters are "neutral" in terms of color bias. This is often a problem with other graduated filters (particularly the lower priced ones) which often tend to distort or exaggerate the colors in a scene.
Like any creative tool, the Reverse ND Graduated Filter will not solve all your photographic problems. However, with some imagination, creativity and experimentation, they will greatly help expand the possibilities of what you can successfully translate from your mind's eye to film.
-- Daryl Benson
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