Black and White Photography

Within limits, you have the ability to vary the lens aperture, focusing distance,

or focal length, either to maximize depth of field or to focus selectively.

But sometimes additional limiting factors come into play. Subject lighting is

one. Brighter lighting usually requires a smaller lens aperture, which delivers

greater depth of field—whether you want it or not. Film speed is another

consideration; slower-speed films require more light and thus larger lens apertures,

which produce less depth of field.

Furthermore, a subject that requires you to move closer, such as a flower,

decreases your depth of field because of the close focusing distance, while a

subject that requires you to be further away, such as a landscape, results in

greater depth of field. Your choice of composition also may weigh in. If you like

to show a lot of the environment around your portrait subject, for example,

you will create greater depth of field by moving further away or using a wideangle

lens; if you like framing your subject tightly by moving in closer or using

a telephoto lens, you will get less depth of field.

Often you won’t have to worry about having enough depth of field. Chances

are you will have enough if you are using a medium-to-small f-stop and if you

are far enough away from your subject, or if you are using a wide-angle lens

(35mm or wider). With experience, you will learn to estimate the impact of

these factors. Guess focusing is one method of using the depth-of-field factors that allows

you to work quickly without ever looking through the camera to focus. Start

by guessing how far the camera is from your subject and set that distance on

the lens distance scale, the ring or window on the side of the lens that indicates

how far away the lens is focused. Then choose the smallest lens aperture you

can use that would still be practical for the lighting conditions (a large f-stop in

low light or a small one in bright light). If your distance guess is close enough

and the lens aperture small enough, your subject should be acceptably sharp—

most of the time. Using a wide-angle lens makes guess focusing more accurate

by providing inherently more depth of field.

Say your subject seems about 8 feet away. Set the distance scale at “8,” set as

small a lens aperture as you can, then quickly take the picture without looking

through the viewfinder to focus. Quickly is the operative word, as guess focusing

allows you to work so your subject will barely notice he or she is being

photographed. You may make some bad guesses along the way and get a few

out-of-focus pictures, but when you are successful your pictures will have a

spontaneity and candidness that you may not get if you have to spend time

focusing. One way lenses are described is by their maximum aperture, which represents the

maximum amount of light they will allow through. A lens with a maximum aperture

of f/2 (called an f/2 lens) allows more light through (when set at f/2) than an

f/4 lens. The larger the maximum aperture, the faster the lens.

Different model lenses of a particular focal length may have very different

maximum apertures, even if they are made by the same manufacturer. There are

very fast 50mm lenses, for example, that open up to f/1.2 and f/1.4, and there are

slower 50mm lenses that open to only f/2 or f/2.8.

Zoom lenses usually have a smaller maximum aperture than fixed focal-length

lenses. Also, many zoom lenses have a variable maximum aperture, which is dependent

on the focal length that is set. Generally, the longer the focal length, the

smaller the maximum aperture. A 35–135mm zoom, for example, may be designated

as an f/4–5.6 lens; set at 35mm, it has a maximum aperture of f/4, but set

at 135mm it has a slower maximum aperture of f/5.6. The maximum aperture

varies at in-between settings, such as f/4.5 when set at 75mm.

Bulkier and more expensive zoom lenses may have a fixed maximum aperture.

Some models of the popular 16–35mm focal-length lens, for example, open to a

maximum of f/2.8 regardless of what focal length is set. One model zoom may

open to f/2.8 and another offering the exact same zoom range may open to a

variable f/4 –5.6, which is even the case with lenses from the same manufacturer.

Most photographers do all their work with standard fixed-focal-length or zoom

lenses. But you also may want to explore one of several special lenses available

for specific situations. Following are some of the most common.

Macro lens. Most lenses for SLR cameras focus no closer than about 12 to 18

inches (or even further) away, and you can’t even get that close with longer SLR

lenses and lenses for most point-and-shoots, rangefinders, and twin-lens-reflex

cameras. There are accessories that allow you to focus more closely, but the

simplest way is to use a macro lens, a lens specially designed for the task. There

are fixed-focal-length macro lenses that focus quite close, as close as an inch or

two away from the subject in some lengths; however, most macro zoom lenses

don’t focus as close.

You can use almost all macro lenses like any other lens to focus at any distance.

But unless you plan to focus close up, buy a nonmacro lens instead.

Macros are more expensive and often have a smaller maximum aperture than a

comparable fixed-focal-length lens. True macro lenses are generally available in

normal or slightly telephoto sizes, such as 55mm and 100mm.