Low Light & Fast lenses
Dick Stolley who many consider to be Time-Life’s best Managing Editor once told People magazine’s photographers that a successful image elicited a “Gasp Factor” from the viewer. Stolley said if the image stopped the reader, forced them to take a second look at it, read the story’s headline, and then perhaps the rest of the story, the photograph passed his test. Often the best photographs—those “Gasp Factor” ones—are made under less than ideal lighting conditions. These images are often made on dark cloudy stormy days, at the crack of dawn, at sunset, or in the dark of the night.
There are few if any secrets about capturing images when light is low. The ingredients are a simple witches brew that include fast lenses, high ISO settings, and an appropriate camera support. What sets a successful image apart from a less successful one is how these ingredients are combined and what you did before the image was made. A sunset can happen rather quickly, so it’s important to have most of your work done ahead of time. Before snapping the shutter, you should already know which ISO setting and lenses you’re planning to use so that’s why it’s a good idea to scout the location and determined the best spot to place your camera. Knowing the exact time of sunset will let you be in position so that when that golden hour arrives (and quickly departs) you are free to concentrate on the proper exposure and properly framing the image.
Just as with sports cars, bullet trains, and Internet connections, being fast is great for camera lenses too. It’s much easier to take photographs in low light with an f/1.4 or f/2.0 lens than with a f/5.6 lens because it produces a bright viewfinder (or Live View image) and gives you more choices for a matching shutter speed. Lens companies don’t bury us with choices, usually selling just two or three similar lenses in the same focal length range and designed to work under normal lighting conditions. In photographic terms, “normal” means outdoors on sunny day. Out here in the real world where we all live and make photographs, “normal” lighting may be overcast weather, under the shade of trees or buildings, or in brightly lit rooms (one with skylights or maybe large and plentiful windows.) Basic zoom lenses supplied on point-and-shoot cameras and bundled with entry level SLRs have maximum apertures ranging from f/3.8 to f/4, f/4.5, and even f/5.6. Some point-and-shoots cameras only have an f/6.3 maximum aperture!
Not surprisingly, zoom lenses for SLRs come in fast or slow varieties. Many of the slower zoom lenses have a floating maximum f/stop. That means the maximum opening changes within the lens’ zoom range. A 24-105mm f/3.5-5.6 zoom lens is a good example. At the widest focal length of 24mm the maximum aperture is the f/3.5. As the lens is zoomed toward the telephoto end, that maximum aperture shifts to f/5.6. The downside is that fast lenses cost more and with digital SLR’s performance getting better and better at high ISO’s, is the fast lens going to go the way of the passenger pigeon? I don’t think so because; right now anyway, nothing can replace that big, bright image in the viewfinder.
Joe is the co-author of “Better Available Light Digital Photography” published by Focal Press.