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Wednesday, August 1, 2007

Extreme Neutral Density

Taking super-long exposures with ND filters can add an artistic component to your photography


Cap-Bon-Ami, Forillon National Park, Qu√(c)bec, Canada

Cap-Bon-Ami, Forillon National Park, Quebec, Canada
Camera, lens and filters were only about one foot above the pebbles during this four-minute exposure of incoming surf at sunrise. Canon EOS-1Ds Mark II, Canon EF 16-35mm ƒ/2.8 lens at 16mm, ƒ/8, four-minute exposure, Singh-Ray Vari-ND at about -5 stops, Singh-Ray Gold-N-Blue color polarizer, two-stop soft-edge grad. Vignetting and a few small water drops that accumulated on the filter during the exposure were later cleaned up in Photoshop.

Fish don't see water, birds don't see air, humans don't see time...but photography does.

When a film or digital sensor is exposed to light, a subject is recorded in relation to time. For example, a bird in flight photographed at 1/4000 of a second looks entirely different than if photographed in the same situation at 1/8 of a second. The difference is time. A film or digital sensor can record the passage of time, be it seconds, minutes or hours.

I’ve been experimenting with using extreme neutral-density (ND) filters—solid ND, not graduated—to increase daylight exposures from fractions of a second to many minutes long! In the middle of a bright, sunny day, with your lens stopped down to its minimum aperture (say, ƒ/32) and a slow ISO setting (50 ISO), you may get down to a shutter speed of 1/15 or 1/8 of a second. By putting a polarizing filter on the front of the lens, you can reduce the amount of light entering the camera by another 2 to 2 1/2 stops. This will increase the exposure time by an additional 1/2 to full second—a slow enough shutter speed to capture a nice, silky veil of water if photographing a waterfall.

As with many techniques, however, there’s more to be explored if you can push the boundaries. The idea of extremely long exposures isn’t new, but playing with this element during midday poses some interesting possibilities, such as fields of wildflowers blowing in the wind during a five-minute exposure, billowing cumulus clouds streaking through a midday sky in a 15-minute exposure and the tide washing in along a beach during an hour-long afternoon exposure.

Kodak manufactures a series of Wratten ND filter gels ranging in density from ND 0.10 (1/2 stop) all the way up to ND 4.00 (-13 1/3 stops)! To give you an idea of how much density ND 4.00 is, consider a maximum exposure time of one second under normal daylight. By putting an ND 4.00 over the lens, your exposure would drop to more than two hours! This represents a filter factor of 10,000!

Lupine, Prince Edward Island, Canada Sunrise, Waterton Lakes National Park, Alberta, Canada
Lupine, Prince Edward Island, Canada
Lupine blowing in the wind during a 10-minute midday exposure. The fence post gives visual anchor to the chaotic motion of flowers and foreground grasses. Canon EOS-1Ds Mark II, Canon EF 24-70mm ƒ/2.8L lens at 35mm, ƒ/22, 10-minute exposure, Kodak ND 4.00 filter (-131/3 stops)
Sunrise, Waterton Lakes National Park, Alberta, Canada
Pentax 645N, Pentax 80-160mm ƒ/4.5 lens at 80mm, ƒ/32, four-minute exposure, Singh-Ray 5-stop solid ND filter, Singh-Ray Gold-N-Blue color polarizer, Fujichrome Velvia 50, ISO overexposed one stop for reciprocity

Singh-Ray’s glass Vari-ND filter can increase exposure times from two to eight stops by rotating the filter like a polarizer. It’s threaded in both directions so other filters can be added. Singh-Ray also makes a single five-stop ND filter that can be threaded to the front of the Vari-ND to increase the filter strength by seven to 13 stops!

Lee Neutral-Density Soft Grad SetEssential Gear...
Lee Neutral-Density Soft Grad Set: This collection of 4x6-inch rectangular grad ND filters uses a soft graduated diffusion to smoothly reduce light from top to bottom. Stepping down exposure by one stop each, the slides mount to a bracketing system for ideal placement of the diffusion line. Estimated Street Price: $95. Contact: Lee Filters, (800) 576-5055, www.leefiltersusa.com.

Singh-Ray Vari-NDSingh-Ray Vari-ND: Designed to be the only solid neutral-density filter that you may need, the Vari-ND twists to alternate polarity, stepping light loss all the way from two to eight stops, and everything in between. Estimated Street Price: $340 (77mm ring mount); $390 (wide-angle ring mount). Contact: Singh-Ray, (800) 486-5501, www.singh-ray.com.

B+W Graduated ND 501 (0.3-2x) and 502 (0.6-4x)B+W Graduated ND 501 (0.3-2x) and 502 (0.6-4x):
The B+W Grad ND 501 slows light
by 50 percent and the 502 steps light loss down to 75 percent. That translates to a one- or two-stop difference, perfect for bright skies that will blow out when exposure is being metered for shadowy foregrounds. Estimated Street Price: $49 to $203, depending on lens diameter. Contact: B+W (Schneider Optics), (631) 761-5000, www.schneideroptics.com.


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