Getting Your Pix Onscreen

Scanning creates digital images from negatives, transparencies, or prints. When images are scanned, their tones and colors are
converted into numbers that the software can edit. A scanner captures
samples of brightness and color in a regular grid pattern. The more
samples the scanner takes, the more detailed the scanned image is.
Image quality depends on the quality of the scan. Just as you can’t get
a good darkroom print from a poor negative, you can’t get a good
image from a bad scan, or even a good scan from a bad negative or
print. Scans made from poorly exposed or badly scratched film require
extra time to edit and rarely produce acceptable results.The scanning process is much easier if you know
beforehand how the image will be used. A
proper scan is the best starting point for editing
a print or negative, if you’re still using film cameras.
If the final result is to be realistic, the scan
should produce an image as close to realism as
possible. If the final result is to be a colorful
departure from reality, the scan should be as
close to the intended colors as possible.
Before you scan an image, you also need to
know how it will be presented. Will the final
image be viewed on a Web site or printed in a
publication? Will it be exhibited as a fine print, and if so, how large will it be? A
digital image has no real physical size until you print it or show it on a monitor.
Potentially, it might be printed or displayed in many sizes, but if you select the
wrong settings, you might end up with a sub-par image. Your scanning decisions
must be based on both the physical size you want and the characteristics of the
printer or display device.
Working with Scan Software
Scanning software is simplified image-editing software . To get a good
scan, you might need to adjust the size, brightness, contrast, and overall color balance
of a negative or print before you actually scan it. Fortunately, these basic
adjustments are available in good scanning software.
Two types of scanning software come with scanners:
■ Normal. Like ordinary software, you open the scan software, wait for it to
find the scanner, scan the image, and save the image as a file for editing.
■ Plug-in. Many scanners include plug-in software that works in conjunction
with another program. You must open your favorite image-editing software
(Photoshop, Photoshop Elements, iPhoto, and so on), choose File, Import, and
then select the scanner’s plug-in software from a list. Once chosen, the scanner
plug-in will hide the image-editing software and display its own interface
and controls. When scanning is complete, the plug-in software will exit,
return to your image-editing program, and display the new scan, ready for
editing.
Scanning is not difficult. The best approach is to practice scanning different types of
prints, different size prints, and negatives (if possible).

Film Latitude

Accurate exposure is just as important with color reversal films as it is with digital.
Reversal films also have little exposure latitude—that is, they do not tolerate over- or
underexposure (see Figure 5.3). Colors in a transparency begin to look too dark with
as little as one-half stop underexposure. Because there is little tolerance for overexposure,
colors look pale and bleached out.
Color negative film has much more exposure latitude than reversal film. You will
have a printable negative with as much as one stop underexposure or three stops of
overexposure. However, the best results always come from correctly exposed film.
In contrasting lighting, color reversal film and most digital cameras are not able to
record the full range of brightness. In scenes with very bright highlights (such as
snow or sand) and very dark shadows, the scene’s brightness range (the overall contrast)
is greater than the exposure range of the film or sensor.
If the shadows are correctly exposed the lightest areas will be blank white. If the
light areas are well exposed, the shadows will be featureless black. You can compromise
and expose for the most important part of the scene. You can also bracket
(shoot additional pictures with different exposures). The best solution to greatly contrasting
scenes is to use an electronic flash or a large reflector to add light to the
shadow areas, thus reducing the scene’s contrast
Low-contrast lighting has a smaller tonal range and thus allows film and digital
cameras to easily capture details in both the bright and dark areas. In addition,
such lighting is more forgiving of exposure errors than greatly contrasted lighting.
Fill-in flash can also lighten contrasted shadows.
Even though negative film is more forgiving, remember that you will lose additional
detail when you scan in an image. Scanning an overexposed or underexposed negative
results in loss of detail in shadows and highlights. This situation is even worse
when you scan in prints!

Exposure Latitude

Color transparency film and most consumer digital cameras have little exposure latitude.
Even slight overexposure or underexposure is readily visible, especially in contrasting
lighting. Consumer-level digital cameras blow out highlights in overexposed
prints . A blowout is a dead giveaway the image was taken with a digital
camera.
Some professional digital cameras capture 36 bits per pixel instead of 24, and are
better able to deal with high-contrast scenes than less expensive, point-and-shoot
digital cameras. Even though 24 bits per pixel means millions of color combinations
are possible, 36 bits per pixel increases that capability to billions. As a result, 36-bit
cameras capture what the human eye sees more accurately. This helps color balance
by providing more colors that can be edited and adjusted.

Color Balance and Slide Film

Color balance is more important with reversal film
than with negative film. Because reversal film is viewed directly, any minor color
cast will be noticed. The colors in negative films can be corrected in printing, so negative
films produce acceptable results under a wider range of lighting. Even so, you
get the best colors if film is shot under correctly balanced lighting or if color correction
filters are placed on the lens to correct the color of the light.
The color of daylight changes depending on the weather and the time of day.
Daylight color film is color balanced for average noon sunlight. An hour or two
before sunset, the light becomes very red or yellow. On cloudy days, the color of daylight
becomes much bluer. Color filters can be used to eliminate the bluish color if it
is undesirable.

Color Balance and Film

Color film can record colors that your eye does not
see when the picture is made. This is because film is
manufactured to reproduce color accurately under
specific lighting conditions. If the picture is made
under the wrong lighting, colors in the photograph
become unbalanced, which means that there is an
unwanted color tint (or color cast) over the entire
photograph.
For example, if daylight-balanced film is used
indoors under incandescent light bulbs, objects that
are supposed to look white, such as a white shirt,
will be rendered with a red tint. This is because
incandescent light bulbs produce more light in the
red wavelengths than daylight does.

Exposure and Focus

Color balance and latitude are two important characteristics of film and
digital media. Color balance is the film or CCD’s response to colors in a
scene. Latitude is the amount film or a CCD can be under- or overexposed
and still deliver a decent picture. Digital cameras are capable of
overexposure and underexposure but actually have no more latitude
than print film! For this reason, your images must be technically accurate
for both types of media.
By comparing film and film technologies to the capabilities of digital
cameras, you will certainly learn new techniques to try in digital. This
chapter explains color balance and then examines the capability of both
mediums to handle extreme exposure situations.

Digital Cameras and Color Balance
Digital cameras are not immune to color balance issues, although white-balance
features in most cameras help to reduce problems when used properly. White-balance
enables photographers to set the “white point” for a camera before pictures are
taken. This forces a camera to consider a specific color of lighting as purely white
light.
The purpose of a white point (white balance) is to force the camera sensor to see the
color you designate as pure white. To avoid off-color images taken indoors with fluorescent
bulbs or zenon bulbs, you might need to point the camera at a white object
(such as a piece of cardboard or a white wall), and then set the white balance on the
camera. By setting a white point, the camera will not have color-cast issues later on.
Television news crews, for example, avoid strange colors and skin tones by setting
the white point of their video cameras prior to every shoot.
Most digital cameras can accurately compensate for lighting color and overcome
unusual lighting conditions. However, occasionally their automatic adjustment systems
get confused. This often happens indoors, where lighting systems can vary
greatly. If you’re shooting indoors under unusual lighting, set the white balance on
the camera before taking pictures.
To set the white balance for your camera, follow these general steps:
1. Access the menu on your camera. Usually there is a dedicated Menu button
somewhere on the back of the camera.
2. Scroll through the menus until you find a setting for WB, White Bal, or White
Balance.
3. There might be a few more choices, such as Presets. Continue through the
menus until you reach choices that resemble the following:
■ Auto. Automatically corrects white balance. This setting is often the
only one you need, especially if you photograph outdoors.
■ Daylight. Set the white balance to daylight if you’re shooting outside.
■ Tungsten. Set white balance to tungsten, if you’re shooting indoors
with incandescent bulbs (the screw-in type from GE). These bulbs emit a
lot of yellow light. The tungsten setting will compensate by reducing
yellow and increasing blue.
■ Fluorescent. Set to fluorescent to compensate for the excessive green
output by these tubes.
4. Highlight one of these choices and then press OK. The camera is ready for
unusual lighting.
The color temperature of “white light” is measured on the Kelvin scale . Warm colors of light have low color temperatures; cool colors of light have highcolor temperatures.
Different color films are manufactured for different color temperatures. Daylight film
is balanced for 5,600° Kelvin (or K) light and gives accurate color with midday sunlight
or electronic flash. Indoor film, called Type B or tungsten film, is balanced for
3,200°K light and gives excellent color with professional quartz-halogen lights (powerful
lights up to 1,000 watts). It will give acceptable, slightly warm color with ordinary
incandescent light bulbs, which are 2,500°K to 2,800°K.
Video cameras and some digital cameras have circuitry to automatically adjust the
color balance to match the color of the light source. Digital cameras also provide settings
that enable you to emulate the warm yellow cast of indoor lighting or the
harsh green color common with fluorescent lights. These custom settings resemble
different types of film such as tungsten and indoor film.

Automatic Focus

Automatic focus (AF) does the focusing for you. In the simplest designs, you push
the shutter-release button and the lens snaps the image into focus. The camera
adjusts the lens to focus sharply on whatever object is at the center of the viewfinder
within the focusing brackets. This type of autofocus works well in situations where
the main subject is—and stays—in the middle of the picture. The camera will display
a confirmation light when it has focused, but the light does not assure that the
picture will be sharp overall.
If your subject is not within the focusing brackets, you can use autofocus lock to
make it sharp:
1. Frame the subject within the focusing brackets.
2. To temporarily lock in the focus, press the shutter release button halfway down.
3. Keeping the shutter partially pressed, reframe the scene (move the subject out
of the center), then press the shutter release button all the way down.
Wide-area focus systems provide more elaborate electronics. The viewfinder displays
several focusing brackets. By rotating a dial or thumbwheel on the camera, you select a bracket that covers the subject you want to be sharp. When you press the shutter,the camera focuses on the selected area. This feature allows you to maintain your framing without autofocus locking and reframing each picture. It also allows you toshoot fast-moving subjects that are not in the center of the frame

Some wide-area autofocus systems use the light reflected off your eyeball to determine
where you are looking in the viewfinder, and therefore what aspect of the picture
to bring into sharp focus. Other systems automatically select the nearest subject
in the picture and focus there.

Types of Autofocus

Your camera might let you select among manual, single-shot, and continuous focus.
With single-shot autofocus, sometimes called focus priority, the camera will not let
you take a picture until it has focused. After the lens locks in the focus, you must
either expose the picture or let up on the shutter-release button. This assures you of
a high percentage of sharp pictures, but can prevent you from capturing a critical
moment.
With continuous focus, the camera constantly searches for the correct focus when
you partially depress the shutter button. The camera revises its focus as the subject
moves closer or farther away. Continuous focus allows you to make an exposure
whenever you like. This approach works well for shooting action but does not guarantee
a sharp picture every time.

After you lock onto a subject, some cameras predict where the subject
is likely to be next, keeping the subject in focus even if it moves
across the frame. These focus tracking systems can
lock onto a subject, adjusting the focus as the
subject moves closer to, or farther from, the camera.
The system works especially well if the subject,
like a race car, is traveling at a constant
speed toward or away from the camera.
Some cameras have two autofocus systems.
Active autofocus sends out a beam of red light
that the camera uses to measure the distance to
the subject. Passive autofocus uses the contrast in the
scene to determine when the subject is sharp.
Autofocus systems are not infallible. Active autofocus
is limited to subjects fairly close to the camera.
Passive autofocus is limited by the brightness and
contrast of the subject. A camera might fail to focus
or miss the focus if a subject has very low contrast,
is in very dim light, or consists of a repetitive pattern
like window blinds or a complex pattern, like
a plaid. Some cameras employ both systems for
maximum sharpness under most conditions.
Read your camera’s instructions to know how its
autofocus mechanism operates and when you
would be better off focusing manually.

Center-Weighted Autofocus Lock
Autofocus cameras often focus on the center of a scene. This can make an off-center
main subject out of focus if it is at a different distance from whatever is at the center. To focus properly on the subject of your picture if he/she/it is not in
the center of the image:
1. In autofocus mode, first focus by placing the autofocus brackets on the main
subject. With many cameras, you partially press the shutter button down.
Keep partial pressure on the release to lock focus (Figure 4.10).
2. Reframe your picture (see Figure 4.11) while keeping partial pressure on the
shutter release.
3. Push the shutter button all the way down to make the exposure.

Focus and Depth of Field
What exactly is sharpness, and how much can it be controlled? In theory, a lens can
only focus on a single distance at a time (the plane of critical focus) and objects at
all other distances will be less sharp. However, in most cases, part of the scene will
be acceptably sharp both in front of and behind the most sharply focused plane.
Objects will gradually become more and more out of focus the farther they are from
the most sharply focused area.
Depth of field is the part of a scene that appears
acceptably sharp in a photograph. Depth of field can
be shallow, with only a narrow band across the
scene appearing to be sharp, or it can be deep, with
everything sharp from nearest to farthest. To a
large extent, you can control how much of it will
be sharp. There are no definite endings to the
depth of field; objects gradually change from sharp
to soft the farther they are from the focused distance.

Controlling Depth of Field
Evaluating and controlling depth of field is more
important in some situations than in others:
■ If you are relatively far from the subject, the
depth of field (the distance between the nearest and farthest points in a scene
that appear sharp in a photograph) will be greater than if you are up close.

■ If you are using a short focal-length lens, you will have more depth of field
than with a long lens.
■ If the important parts of the scene are more or less on the same plane left to
right, they are all likely to appear sharp as long as you have focused on one
of them.
But when you photograph a scene up close, with a long lens, or with important
parts of the subject both near and far, you might want to increase the depth of field
so that parts of the scene in front of and behind the point on which you focused will
also be sharp

Sometimes, though, you will want to blur a distracting background that draws
attention from the main subject. You can accomplish this by decreasing the depth of
field.
You can use the aperture to control depth of
field. To increase the depth of field so that more
of a scene in front of and behind your subject is
sharp, setting the lens to a small aperture is
almost always the first choice. Select f/16 or f/22,
for example, instead of f/2.8 or f/4. You might
have to use a slower shutter speed to maintain
the same exposure, however. A slow shutter
speed can be a problem if you are photographing
moving objects or shooting in low light.

To decrease the depth of field and make less of the scene in front of and behind the
subject sharp, use a wider aperture, such as f/2.8 or f/4.
There are other ways to control depth of field. You can increase the depth of field by
changing to a shorter focal-length lens or stepping back from the subject, although
both of those choices will change the picture in other ways as well.
To decrease the depth of field and make less of the scene in front of and behind your
subject sharp, you can use a longer lens or move closer to the subject. These alternatives
will also change the composition of the picture.

Lens Focal Length, Aperture, and Light
Why does a lens of longer focal length produce less depth of field than a shorter lens
at the same f-stop (aperture)? The answer relates to the diameter of the aperture
opening. The relative aperture (the same f-stop setting for lenses of different focal
lengths) is a larger opening on a longer lens than it is on a shorter lens

Both lenses were set at f/4, let in the same amount of light, even though the actual
opening in the 50mm lens is physically smaller than the opening in the longer
300mm lens.
The longer the focal length, the less light that reaches the film (or CCD chip on a
digital camera), therefore a long lens will form a dimmer image than a short lens
unless more light is admitted by the aperture.
The sizes of the aperture openings are determined so that at a given f-stop number
the same amount of light reaches the film, no matter what the focal length of the
lens. The f-stop number, also called the relative aperture, equals the focal length of
the lens divided by the aperture diameter.

Special-Purpose Lenses

A number of lenses exist that do not fit into the traditional wide-angle, medium,
and telephoto lens categories.

Fisheye Lens
For the widest of wide-angle views, consider the fisheye lens. Super wide-angle lenses
allow the photographer to get very close.
A fisheye lens has a very wide angle of view—up to 180°—and exaggerates to an
extreme degree differences in size between objects that are near to the camera and
those that are farther away. Inherent in its design is barrel distortion, an optical aberration
that bends straight lines into curves at the edges of an image. Two types of
fisheye lenses exist:
■ True fisheye. A circular image is taken and the rest of the frame is black.
Literally, a circle is all you get.
■ Full-frame fisheye. The fisheye lens fills the entire frame. Distortion still
occurs, but the frame has no black, blank areas.
Fisheye lenses also produce great depth of field. Objects within inches of the lens and
those in the far distance will be sharp. It is not a lens for every situation, but it can
produce startling and effective views.

Macro Lens
A macro lens is useful for extremely close shots. The lens allows you to focus at a very
close range (see Figure 4.7) and is corrected for aberrations that occur at close focusing
distances. The lens is occasionally called, somewhat inaccurately, a micro lens.
Some zoom lenses come with a macro feature. They focus closer than normal, but
not as close as a fixed focal-length macro lens.

Soft-Focus Lens
Aberrations are deliberately introduced in a soft-focus lens, also called a portrait lens.
The goal is to produce an image that will diffuse and soften details such as facial
wrinkles.

Perspective-Control Lens
A perspective-control lens brings some view/camera adjustments to other types of cameras.
The lens shifts up, down, or sideways to prevent the perspective distortion that causes parallel lines to tilt towards each other if the camera is tilted. Before Photoshop, these lenses were the only way 35mm and medium-format architectural
photographers fixed the distortion of buildings. These lenses are now essentially
obsolete because you can fix the problem in Photoshop.

Catadioptric (Mirror) Lens
A catadioptric lens (also called a mirror lens) is similar
in design to a telescope. It incorporates curved mirrors
as well as glass elements within the lens. The result is
a very long focal length that is smaller and lighter
than a typical lens of equivalent focal length.
These mirrors come into vogue and then fall back
out again every few years. These lenses are the
smallest telephoto lenses you can buy, but they
have some issues. The front mirror in the lens has
the unusual effect of causing out-of-focus highlights
to take on a donut shape, rather than the
usual disk shape produced by an ordinary lens.
Mirror lenses are also slow because of a fixed aperture.
The aperture is usually f/8 or f/11.

Focal Length and Digital Cameras

Lenses for 35mm cameras have a different focal
length on a digital camera. The CCDs used in these
cameras are physically smaller than a 35mm
frame. For this reason, lenses used on digital cameras
(with removable lenses) have a longer focal
length. In other words, a 50mm lens will actually
be 80mm on some digital cameras.
If you already own lenses for a traditional film camera
and are shopping for a digital camera that will
work with them, find out what the focal magnifier
is for each camera—it varies depending on the
manufacturer and even the model line. CCD and
CMOS sensors in these cameras vary greatly in size.

Long Focal-Length Lenses

A long focal-length lens provides greater image magnification and a narrower angle
of view than a normal lens. For a 35mm camera, a popular and useful long focal
length is 105mm. For a camera using 2 1/4×2 1/4-inch film, the comparable focal
length is 150mm. For a 4×5-inch view camera, it is about 300mm.
Long lenses are excellent when you cannot or do not want to get close to the subject.
They are also preferred for portraits; most people become self-conscious when a camera
is too close to them, so their expressions are often artificial. A long lens also
avoids the kind of distortion that occurs when shorter lenses used close to a subject
exaggerate the size of whatever is nearest the camera—in a portrait, usually the
nose.
Photographing a person at too close a lens-to-subject distance makes features
nearest the camera appear too large and gives an unnatural-looking dimension
to the head.
There are subtle qualities that can be exploited when you use a long lens. Because a
long lens has less depth of field, objects in the foreground or background can be
photographed out of focus so that the sharply focused subject stands out clearly.
Also, a long lens can be used to create an unusual perspective in which objects seem
to be closer together than they really are
Long lenses do have some disadvantages:
■ Long telephotos are heavier, bulkier, and more expensive than normal focallength
lenses.
■ Because they have relatively shallow depth of field, long lenses must be
focused accurately.
■ Long lenses are difficult to use for handheld shots because they magnify lens
movements as well as subject size.
The shutter speed for a medium-long lens, such as a 105mm lens on a 35mm camera,
should be at least 1/125 second if the camera is handheld. For a 200mm lens,
you will need at least 1/250 second. Otherwise, camera movement might cause blurring.
A tripod or other support is your best protection against blurry photos caused
by camera movement.
A tele-extender or teleconverter contains an optical element
that increases the effective focal length of a
lens. It attaches between the lens and the camera
body and magnifies the image from the lens onto
the film. With these devices, the effective length of
the lens increases, but less light reaches the film. A
converter that doubles the lens, for example, loses
two f-stops of light. Regardless, this tiny addition to
your lens collection is welcome. A tele-extender can
turn a normal telephoto into a super telephoto,
which comes in handy if you’re birding, or in a situation
where you’re extremely far away and can’t
get closer to the subject.

Short Focal-Length Lenses

A short focal-length lens increases the angle of view
and shows more of a scene than a normal lens used
from the same position. A short lens (commonly called a wide-angle lens) is useful
when you are physically prevented (as by the walls of a room) from moving back as
much as would be necessary with a normal lens.
For a 35mm camera, a commonly used short focal length is 28mm. A comparable
lens for a camera using 2 1/4×2 1/4-inch film is 55mm. For a 4×5-inch view camera,
it is 90mm.
Wide-angle lenses have considerable depth of field. A 24mm lens focused on an
object seven feet away and stopped down to f/8 will show everything from four feet
to infinity in sharp focus. Photographers who work in fast-moving situations often
use a moderately wide lens, such as a 35mm lens on a 35mm camera, as their normal
lens. They don’t have to pause to refocus for every shot, because with this type
of lens, so much of a scene is sharp. At the same time, it does not display too much
distortion.
Pictures taken with a wide-angle lens can show both real and apparent distortions.
Genuine aberrations of the lens itself such as curvilinear distortion are inherent in
extremely curved or wide elements made of thick pieces of glass, which are often
used in wide-angle lenses. Although most aberrations can be corrected in a lens of a
moderate angle of view and speed, the wider or faster the lens, the more difficult
and/or expensive that correction becomes.
A wide-angle lens can also show an apparent distortion of perspective, but this is
actually caused by the photographer, not the lens. An object that is close to a lens
(or your eye) appears larger than an object of the same size that is farther away.
Because a wide-angle lens can be focused close to an object, it is easy to get this kind
of exaggerated size relationship. The cure is to learn to see what the camera sees
and either minimize the distortion, or use it intentionally.

The Important of Lenses

Good photographers know their cameras and how they work. This
chapter explains the science behind the most important part of that
equipment: lenses. The more you know how to work with lenses, the
better a photographer you will be. Fortunately, even beginners have
been exposed to what this chapter covers:
■ Focal length. You probably have heard the numbers surrounding
lenses, such as a 28mm lens and a 400mm lens. You might
have heard the terms wide-angle and telephoto used instead of
these numbers.
■ Aperture and depth of field. Open the lens to f2.8 and see
depth of field disappear.
■ Focus. Focus by hand or use autofocus.
■ Special lenses. Use special lenses for close-ups, panoramas, and other special
images.
Carpenters must know their tools to stay in business. The same can be said for professional
photographers. Besides your creativity, nothing influences the quality of
your imagery more than the lens. Studying the characteristics of lenses will make you a better photographer.

Lens Focal Length

The most significant difference among lenses is their focal length. A lens is often
described in terms of its focal length (such as a 50mm lens) or its physical length
(short, medium, long). Technically, focal length is the distance between the lens’s rear
nodal point and the focal plane when the lens is focused on infinity (a far distance
from which light reaches the lens in more or less parallel rays).
The focal length controls magnification, or the size of the image formed by the lens.
The longer the lens, you will find the size of objects in the image greater. A lens of
longer focal length bends light rays less than a short lens does (see Figure 4.1). The
longer the focal length, the less the rays are bent, the farther behind the lens the
image is focused, and the more the image is magnified (see Figure 4.2). The size of
the image increases in proportion to the focal length. If the subject remains at the
same distance from the lens, the image formed by a 50mm lens will be twice as big
as that from a 25mm lens.
Focal length also controls the angle of view, the amount of the scene shown on a given
size of film. A long-focal-length lens forms a larger image of an object than a short
lens. As a result, the long lens must include on a given size of film less of the scene in
which the object appears. If you make a circle with your thumb and forefinger and
hold it close to your eye, you will see most of the scene in front of you—the equivalent
of a short lens. If you move your hand farther from your eye, the circle will be
filled by a smaller part of the scene—the equivalent of a longer lens. You will have
decreased the angle of view seen through your fingers. In the same way, the longer
the focal length, the smaller the angle of view seen by the lens.
The effect of increasing focal length while keeping the same lens-to-subject distance
is an increase in magnification and a decrease in angle of view. Because the photographer
did not change position, the size of the objects within the scene remained the
same in relation to each other. Less is visible in the frame as lenses increase in focal
length.

Normal Focal-Length Lenses

A normal focal-length lens, also called a standard focal-length lens, approximates
what the human eye sees. One of the greatest modern photographers, Henri Cartier-
Bresson, who described the camera as “an extension of my eye,” almost always used
a normal lens. The angle of view of most of his images is about the same as what
the eye can see clearly from one position, and the relative size of near and far
objects seems normal.
A lens that is a normal focal length for one camera can be a long focal length for
another camera (see Figure 4.3). Film size determines what will be a “normal” focal
length. The larger the size of the film format, the longer the focal length of a normal
lens for that format. If the focal length of a lens is about the same as the diagonal
measurement of the film (broken line), the lens is considered “normal.” It collects
light rays from an angle of view of about 50°, the same as the human eye.
Usage varies somewhat. For example, lenses from about 40mm to 58mm are also
referred to as normal focal lengths for a 35mm camera.
A lens of normal focal length has certain advantages over lenses of longer or shorter
focal length. Normal focal length lenses have the following characteristics:
■ Faster. They open to a wider maximum aperture, so they can be used with
faster shutter speeds or in dimmer light than lenses that do not open as wide.
■ Less expensive. The lenses are the least expensive of all lenses because they
are manufactured in such large quantities.
■ More compact. Normal focal length lenses are often the smallest lenses
available. If you’re traveling with a 35mm camera, a 50mm is a must-have.
■ Lighter. These lenses often weigh less than even wide-angle lenses!
What you choose for your lens suite is a matter of personal preference, however.
Some photographers habitually use a shorter focal length because they want a wide
angle of view most of the time; others prefer a longer focal length that narrows the
angle of view to the central objects in a scene. If you have a 35mm camera, a 50mm
lens is a good focal length to start.