How to Make a Long Exposure

Pictures of moonlit landscapes or dimly lit interiors need exposures that are longer than the usual handholdable ones. But with the support of a tripod, long exposures also help you create magical effects. You can fill a highway with luminous ribbons of car lights; record multiple bursts of fireworks; smooth out turbulent water until it's silky; allow stars to trace circular paths in the sky; and blur moving people and speeding cars, even making them dis-appear altogether.

Many SLRs and high-end point-and-shoots can automatically time expo-sures up to 4 or 8 seconds, and top-of-the-line SLRs may let you go to 30 seconds or more. If your camera does-n't have this capability, it probably does have "T" (Time) or "B" (Bulb). Either will let you keep the shutter open as long as you like. With Time, you press the shutter release to start the exposure and touch it again to stop it; with Bulb, the shutter stays open as long as you keep your finger on the button. Many point-and-shoots also have Bulb.

How long should you leave the shut-ter open? When your objective is to record a dimly illuminated scene, such as a landscape at night, determine your exposure as you would for a well-lit scene. With sufficient ambient light and fairly even illumination, you may be able to use your in-camera meter. But if some areas are much brighter than others, meter those bright spots with a spotmeter or take a reading off some-thing of equal brightness nearby.

If the long-shutter-speed capability of the camera is not long enough, go to Time or Bulb, figuring out the exposure time with a sensitive handheld meter or with the times given on our chart. Bracket your exposures. If you expose a night scene "correctly" according to the meter, it's going to come out look-ing like daylight. You'll probably prefer an exposure that's darker.

When it comes to creative long exposures, there isn't one right shutter speed for a particular effect; those taken at several different speeds can all be interesting. Shoot five or six frames, doubling the time for each and adjusting the aperture to keep the exposure constant. To blur move-ment-people walking, vehicles mov-ing, water flowing, flowers swaying in the breeze, blowing sand or snow- begin at 1/4 second, then go to 1/2, 1, 2, 4,and 8 seconds.

To make long exposures in the day-time, you'll need slow film (ISO 100 is good) or a neutral density filter over the lens to cut some of the light. At night, you can go to a faster film.

Since none of the shutter speeds mentioned above are handholdable, you'll have to put your camera on a tri-pod or other sturdy support if you want the non-moving parts of the scene to be sharp. (Use a cable release.) But you may want to create an overall blur for abstract pictures of lights by handholding the camera and deliberately moving it during an expo-sure of several seconds.

A special-effects filter, such as a star or diffraction-grating type, can often make a sensational picture when there are many bright lights in a night scene. Adding a burst of flash to the night scene can make a person or tree in the foreground brighter than back-ground objects. During very long (more than 10 seconds) exposures, be on alert for headlights or other bright lights that might move into your scene. You don't have to stop the exposure; just hold a dark hat in front of the lens until the danger has passed.

LONG EXPOSURE TIMES FOR HARD-TO-METER SUBJECTS

SUBJECT	ISO 400	ISO 1000
Home interiors at night, average lighting	1/4 sec f/5.6	1/8 sec f/5.6
Home interiors at night, bright lighting	1/8 sec f/5.6	1/15 sec f/5.6
Indoor Christmas lights and trees	1/8 sec f/5.6	1/15 sec f/5.6
Outdoor Christmas lights and trees	1/15 sec f/5.6	1/30 sec f/5.6
Candlelit close-ups	1/8 sec f/5.6	1/15 sec f/5.6
Subject lit by street lights	1/4 sec f/4	1/8 sec f/4
Subject lit by street lights	1/4 sec f/4	1/8 sec f/4
Floodlit buildings, fountains, monuments	1/4 sec f/4	1/8 sec f/4
Skyline - distant view with windows at night	2 sec f/4	1 sec f/4
Moonlit landscapes	30 sec f/4	15 sec f/4
Moonlit snowscapes	15 sec f/4	8 sec f/4
Lightning	B* sec f/11	B* sec f/16
Fireworks	B* sec f/16	B* sec f/22

Regard these exposures only as starting points, and bracket. If you can use a wider aperture, shorten your exposure accordingly. To photograph fireworks or lightning, open the shutter on B and keep it open long enough to capture single or multiple bursts. For streaking patterns of moving traffic, use ISO 100 film and experiment with exposure times or 10 and 20 seconds with the aperture closed down to f/16.