Getting Started: Lenses: Long and Short, Wide and Tight

Unpacking your first camcorder, you figure out where to insert the battery, fire up your new treasure and peer through the viewfinder. (If you're like most brand-new camcorder owners, you probably think something like, cool!)

What next? You probably try the zoom lens. Pushing the forward half of its control, you zoom in, progressively enlarging the picture in the viewfinder while showing less and less of the overall scene. Pressing the rear half of the control, you zoom out. This shows ever more of the scene, while everything in it gets smaller and smaller. You zoom in, zoom out, zoom in, zoom out, probably still thinking, cool!

At this point your undercharged battery wheezes and dies and your introduction to videomaking recesses for recharging.

But that's another story. What interests us here is the pictures you get when you zoom--the very different images delivered by telephoto lenses (zoomed in) and wide-angle lenses (zoomed out).

Types of Lenses
That's right--no matter which camera model you bought (with just one or two exceptions) you have acquired a wide-angle lens, a telephoto lens, and every kind of lens in between as well. That's because your camcorder's zoom is technically a "variable focal length" lens, and at the ends of its range of variation are wide-angle and telephoto settings.

Many camcorder owners never progress beyond those first discoveries of yours. They zoom in (to telephoto) to enlarge details while narrowing the view, and they zoom out (to wide angle) to broaden the view while shrinking the details. Basically, these people use their zoom lenses for just one thing: to get "closer to" or "farther away from" their subjects without actually moving the camera.

But zooming changes much more than the breadth of view and the size of objects within it. Shifting between wide and narrow lens angles alters the fundamental qualities of the images you record, because each type of lens has distinct and very different traits. If you understand these traits, you can exploit them creatively to make better videos.

Both wide-angle and telephoto lenses produce "abnormal" (apparently distorted) pictures. But before we describe them, it'll help if we establish a standard of comparison: the undistorted pictures delivered by so-called "normal" lenses.

Normal lenses approximate the view of a single human eye because they cover an angle of about 50 degrees. (Our vision actually covers a span much greater than 50 degrees because we use two eyes rather than just one.) For this reason, images made with lenses covering perhaps 45 to 55 degrees look subjectively normal--they resemble what we see when looking at the world with one eye open.

Angles of View
Since normal lenses cover about a 50 degree angle of view, we can say that lenses with angles of view greater than 50 degrees are "wide angle" and lenses with smaller angles of view are "telephoto." (To contrast with the term "wide angle," telephoto lenses should really be called "narrow angle" lenses instead, but that term appears only in academic texts. The real world calls them telephotos.)

At this point you may be tempted to say, "who cares what anybody calls them? In fact, who cares about abstractions like 'angles of view?'" Bear with me. Wide-angle and telephoto lens settings will have a direct and dramatic effect on the video images you make. But in order to explain how to control them, we have to add just two more preliminary points.

First, the terms "wide angle" and "telephoto" are only relative; each term covers a whole range of lens angles of view. That is, a lens with a 30-degree angle of view is a telephoto (albeit a mild one) and so's a lens with a 2-degree angle. (A super telephoto like the 2-degree model would probably be an telescope with a camcorder attached.)

Similarly, a wide-angle lens may cover anywhere from perhaps 70 degrees to about 150. (The 150 degree lenses are the so-called "fisheyes" that turn flat horizons into bowls.)

Secondly you need to understand that the names given to lenses (like so many other terms in photography) are not intuitive--not accessible through simple common sense. Specifically, lenses are not labeled by the angles of view that we've been explaining, but by their "focal lengths" (an optical technicality that need not detain us here).

The result? The numbers that name the lenses get larger as the numbers that describe their viewing angles get smaller! For example, if you have an 8mm camcorder, your lens may resemble the one in this table:

Just remember that when you see a lens with a low-number name (4mm, 5mm, 6mm) it's a wide- angle lens. If it has a high-number name (30mm, 40mm, 50mm) it's a telephoto lens.

With these preliminaries out of the way, we're ready to contrast telephoto and wide-angle lenses by comparing the ways they handle apparent depth and movement.

Lenses and Depth
There is, of course, no actual depth in a video image. The car speeding away from the camera is not receding from the surface of the screen, but only growing smaller on that surface.

Savvy videomakers use all kinds of techniques to create the illusion of depth in their images, one of which is to use wide-angle lenses. That's because, with a wide-angle lens:

• Objects at different distances from the camera appear to shrink in size much faster than they do in the real world.
  
• The distance between these objects seems much greater than normal.

Together, these two traits of wide-angle perspective exaggerate apparent depth. To see how lenses render depth in two-dimensional images, check out figure 2. In all three photos, the people are standing in exactly the same spots. Figure 2b depicts depth much as our eyes see it in the real world. In the wide-angle view of figure 2a, by contrast, the rear figure seems very tiny and exceedingly far away.

What can you do with these quirks of wide-angle lenses? You can make everything look more spacious than it is, for one. If you've ever compared a brochure photo to the actual reality of a cruise ship cabin, a motel room, or a motor home interior you've seen how a wide-angle lens can turn a phone booth into a blimp hangar.

As for a telephoto lens, its effect is just the opposite, as you can see from figure 2c. Here the figures shrink much more slowly as they recede from the picture plane and the space between them is somehow squeezed out. The result is a strange flatness is if a giant had stomped on the image.

Telephoto lenses are great when you want to conceal distance. For example, imagine a profile shot of two cars hurtling toward an unavoidable head-on crash. But when the fatal moment arrives the two cars pass each other harmlessly. How come? Because a telephoto lens compressed the depth in the shot, concealing the fact that the cars were not really face to face as they appeared, but in two adjacent lanes instead.

Telephoto lenses are good at creating a feeling of crowding and congestion. For instance, cliché shots of the streets of New York City use very long telephoto lenses to squeeze hundreds of pedestrians into what looks like 20 feet of sidewalk.

As you experiment with video composition, you'll discover perhaps the most powerful ability of telephoto lenses. They can turn your monitor screen into a surface like a canvas, on which to create visual designs. By pressing the depth out of the image, the long lens stacks it up on the plane of the screen. Think of a car commercial showing the product snaking back and forth on your screen down a switchback mountain road, and you can imagine the effect.

In fact it's hard to imagine any kind of depth without movement, because videos are, in fact, moving pictures. And how that movement appears in the third dimension is also controlled by lens selection.

Lenses and Movement
Wide-angle lenses exaggerate depth and telephotos compress it, as shown in figure 2. With this in mind, imagine that the rear person walks up to join the front person.

In the actual world where the shot is taped, she covers a certain distance to reach the front person, regardless of the lens used. But in the wide-angle shot the distance traveled appears four times as great as in the telephoto shot. Since she covers the distance in the same time in both shots, the wide-angle lens makes her seem to be moving four times as fast.

That is why wide-angle lenses are routinely used for chase and fight scenes--and why directors try to stage the action in depth. By increasing apparent distance, they make movement appear more dynamic and exciting.

To study this, use your imagination on the four images in figure 3. Figures 3a and 3b represent a wide-angle view of a car driving toward the camera. Figures 3c and 3d show exactly the same movement, but as seen by a telephoto lens instead.

In both pairs of pictures, the car begins at exactly the same spot on the street and travels toward the camera for the same length of time. As you mentally supply the movement between start and end points, notice how much more dramatic the wide-angle version is.

Sometimes, however, you want the opposite effect as supplied by a telephoto lens. For example, imagine an ominous 18-wheeler truck coming toward the camera on a desert highway. Photographed with a long telephoto lens, the truck does not appear to get any closer. Instead, it grows bigger and bigger in the frame, as if inflating itself to ever more menacing size.

Perspective: It's Quite Apparent
A while ago a Videomaker reader pointed out that lenses of different focal lengths only seem to render perspective differently. In fact, the only true difference between wide-angle and telephoto lenses is in angle of view.

The apparent differences in the way these lenses render depth, size, and movement result solely from the fact that narrow angle (telephoto) lenses do not show objects that are very far off the center axis (dead ahead). Wide-angle lenses, by contrast, show things much farther to the sides. The farther off the lens axis an object is, the more extreme its perspective becomes. This fact is what gives narrow angle and wide- angle lenses their distinctive looks.

Technically, the reader was quite correct, and you can easily see what he meant by turning your own "normal angle" eye into either a telephoto lens or a wide-angle lens, depending on its distance from what it's looking at.

To obtain a telephoto effect, place the tips of your two index fingers and two thumbs together to form a tiny viewing frame. Using just one eye, frame a minute section of some faraway prospect (trees on the hillside, shops on a far-distant cross street, phone poles at the limit of visibility).

Now study the view in your frame. If you look carefully, you'll see that more distant objects seem almost as big as nearer ones, and that the space between them appears compressed. Your "normal" eye is delivering "telephoto" perspective because your entire viewing field is filled by subjects on or close to the axis of vision.

Want to see wide-angle? Simple! Hold the eraser end of a pencil at the outer edge of one eyebrow with the pencil pointed forward and slightly downward into your field of vision. Now study the pencil with the other eye closed. Though blurry at this close distance, the pencil will appear as immensely long as the Empire Battle Cruiser sweeping into the top of the frame at the opening of Star Wars. Its apparent length is exaggerated because it is so far off your vision axis.

When all this is said and done, however, the fact remains that wide-angle lenses appear to exaggerate depth and motion, while telephoto lenses appear to compress them. And in a two- dimensional visual medium like video, appearances are, quite literally, everything.

Good News/Bad News
Both wide-angle and telephoto lenses have their good and bad points, so there are times when you want to use each type and other times when you want to avoid it.

Wide-angle lenses offer several benefits:

• They enhance the feeling of depth in your compositions, and that makes your video images seem more realistic.
  
• They make for dramatic compositions, especially when you're shooting buildings or other things with lines that recede from the camera.
  
• They dramatize movement toward and away from the camcorder--great for dynamic action sequences.
  
• They allow you to include more of the scene when you're forced to shoot in restricted environments like small rooms.

Wide-angle lenses also have a few drawbacks:

• They are dangerous when brought too close to people because they exaggerate human facial features in unflattering ways.
  
• They encourage long shots--panoramic compositions in which individual subjects (mainly people) are small. Because video is not very good at capturing fine detail, the smaller something is on the screen, the more fuzzy and indistinct it appears.

Telephoto lenses also have pros and cons. On the plus side:

• They can bring small and distant subjects close where the camcorder can capture details.
  
• They tend to make flattering portraits of human subjects, especially at milder telephoto settings.
  
• They encourage pictorial composition on the picture plane (the screen) and create powerful visual effects, such as a full moon looming enormous above the horizon.

Telephoto lenses do have a few drawbacks though:

• When recording people, they must be positioned too far away from their subjects to permit good sound recording with an on-camera microphone.
  
• When hand-held, they greatly magnify the slightest camera vibration and wobble, making for unpleasantly shaky images.
  
• By suppressing apparent depth, they squeeze some of the drama out of action. Baseball, which must be covered by telephoto lenses, is not very visually exciting on television because it is all about batting and throwing balls (and running) in depth. Captured by a very long lens, a mad dash for first base looks like a man hopping up and down in one place.

For the video newcomer, the safest procedure may be to shoot with your lens at a mild wide-angle setting (not as wide as possible). That way, you'll tend to work closer to your subjects, enjoying better audio recordings without suffering the obvious distortions that wide-angle shooting introduces.

The Lens on Your Camcorder
Obviously, your camcorder lens is at extreme wide angle when it's zoomed all the way out. But what is this "mild" wide angle we recommend?

To determine this, you must first identify the "normal" angle setting for your particular camcorder. And to do so, you need to check the technical specifications to find the size of your model's CCD--its recording chip. Why? because it is the size of that chip that determines the "normal" setting on your lens. (If you'd like more details on this, check out "All about Lenses" in the December, 1994 Videomaker.)

Today, most consumer camcorders use 1/3-inch or 1/4-inch chips. If you have a 1/3-inch chip then normal for your lens is around 15mm. If your camcorder uses the smaller size, then 10mm is normal.

For example, a Hi8 format camcorder with a 1/4-inch CCD might have a lens that zooms from 5mm to 60mm. On this lens, a mild wide-angle setting might be 7.5mm, about halfway between extreme wide angle and normal.

The key to mastering your zoom lens is experimentation. Go out and grab footage at different focal lengths, and examine how these focal lengths change your perception of the subject. In no time, you'll be using your zoom lens to do more than just "get closer" to your subject--you'll be controlling the depth and impact of your images.