Digital Photo Tip #30 By Bruce Kirkby Jul 1, 2007

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See The Light

This month’s column introduces the use of Graduated Neutral Density Filters. GNDFs are an important tool for all professional photographers, and the only filters (apart from polarizers and UV/Haze) used by many of them in the field. While this is an advanced technique, there’s no need to feel intimidated. These simple filters are easy to use and provide truly staggering results.  

WHAT ARE THEY? A GNDF is a rectangular sheet of plastic, half clear and half dark (a colour-neutral pigment that does not affect colours), that can be mounted in front of your lens and slid up and down, darkening a portion of the scene in your frame. They’re employed primarily at or near sunset, allowing proper exposure of both a bright sky and a shadowed foreground.

THE SCIENCE Digital sensors (as well as standard film) are limited when it comes to recording areas of contrasting brightness. Your eyes are far, far better—500 times more sensitive, in fact. Technically, your eyes can perceive 12 to 14 stops of tonal difference, while a camera will record only five. This means that while you may see details in shadows, your camera will record only black; where you see clouds and colour in the sky, the camera may pick up only white. Unless a GNDF is used to bring the two exposures closer together, that is.

USAGE HINTS Position the filter so that the GNDF’s darkened portion covers the sky and the clear portion covers the foreground. Getting the transition exactly on the horizon can be tough—try stopping your camera down to f/16 or f/22 and hold-ing the depth of field preview button to see the line more clearly.

GETTING STARTED Renowned adventure photographer GalenRowell was a champion of GNDF, and his website ( mountainlight.com) has plenty of articles to learn more from. As for finding the right product to use, today’s best GNDFs are made by Singh-Ray ( singh-ray.com), and you’ll find more tips on their website.