Getting Started: ZOOM!!

Used skillfully, your camcorder’s zoom lens can set you apart as a savvy shooter.

Today’s little sermon is about selecting a camcorder with the best zoom for your needs.

Whoa, you say, politely concealing your irritation; how come "Getting Started" keeps telling me how to pick a camcorder when it’s now too late? After all, I’m reading your verstunkener column because I already bought one, didn’t I?

Well, yes, that’s true for some readers, though others are quite literally getting started, and that includes shopping for their first camcorder. But even if you’ve already bought a unit, it still helps to relate the abstract ideas you read here to the features of actual hardware.

Whether buying your first camera or your umpteenth, the features of its zoom lens should strongly influence your decision. (All but a tiny number of consumer camcorders come fitted with built-in, non-interchangeable zooms.) In particular, you need to judge each lens by its optical specs, zooming method(s) and filter facility.

Zoom Optics
In any lens, the first optical consideration is its speed. ("Speed" is a typically counter-intuitive photographic term meaning sensitivity to light. A "fast" lens can operate better in dim lighting conditions than a "slower" one.)

A lens’s low-light competence is indicated by its maximum aperture (widest opening), expressed as an "f-stop," and usually printed on the lens. Without getting technical here, the lower the number, the more sensitive the lens; so "f/1.4" is faster than "f/2.0" and "f/1.2" is faster still. (If these numerical differences seem tiny, consider that an f/1.4 lens can admit twice as much light as an f/2.0 lens.)

Why should you care about light sensitivity? Because even in a typical living room at night, you are shooting in low light levels. If your lens is sensitive enough to form a quality image, great. But if it’s not, the camera circuits electronically amplify such light as does come in and the result is a grainy, washed-out picture. The moral: if one of two otherwise similar camcorders has a faster lens (lower f number), choose it.

Another key optical trait is zoom range, which is expressed as a ratio, like 8:1, 10:1, etc. In a 10:1 zoom, for example, an object appears ten times as big on the screen when viewed in the full telephoto position as it does in full wide angle. Obviously, the wider the zoom (image size) range, the more versatile the lens.

To back up a step, we should note that a "wide-angle" lens setting shows everything within a broad horizontal arc--typically 75 to 100 degrees wide. A telephoto lens setting (which should properly be called a "narrow-angle" setting, but isn’t and don’t ask why) captures a skinny arc of subject matter, perhaps 5 to 20 degrees wide. As you can see, if you fill the width of the screen with 5 degrees worth of subject, that subject will appear much bigger than it would as one small part of a 100-degree panorama. Hence, wide-angle equals broad view and small subjects; telephoto equals narrow view and big subjects. Of course, a zoom lens has an infinite number of intermediate angles between full wide and full telephoto.

In evaluating zoom range, beware of misleading labels. All too often, a camcorder is described as having anywhere from a 20:1 to 100:1 zoom. But vendors speak with forked tongue, often omitting the distinction between true optical zooming and electronic image magnification.

In optical zooming, the glass elements within the lens move back or forth to change the magnification of the picture that reaches the imaging chip. Electronic image magnification (often mislabeled "digital zoom") can then enlarge a portion of that picture and fill the screen with it. For example, a "20:1" system may actually have a 10:1 zoom lens, coupled with the ability to electronically double the magnification of the center of the original screen area.

The problem is that electronic "zooming" degrades picture quality quickly and dramatically. So if you need to capture distant images at any cost (say, for sports analysis videos) then the tradeoff is well worth it; but if you care about picture quality, read the fine print that will tell you how much of the advertised zoom range is true optical zoom.

In addition to speed and zoom range, you also need to consider what you might call the lens’s spectrum. In simple terms, how wide is its wide-angle setting and how long is its telephoto?

You see, wide angle and telephoto are not absolute designations. In an 8mm camcorder, 4mm and 6mm are both wide-angle settings, while 40mm and 60mm are both telephoto. One zoom may extend from 4 to 40mm, while another may be 6 to 60. Though both have the same 10:1 zoom range, the 4-40mm is biased toward the wide-angle end (great for handholding and shooting in confined areas) and the 6-60mm favors telephoto (optimal for sports and wildlife shooting). Obviously, you need to choose the compromise that suits your shooting needs.

When you’ve checked a lens’s speed, range and spectrum, you’ve scoped out its optical traits; but before you can make a selection, you need to see how it actually works.

Zoom Mechanics
Most consumer-market zooms are motor driven: press the forward-placed button to zoom in toward telephoto; push the aft button to zoom out toward wide angle. Some have a small toggle switch located at the back of the camcorder that you can operate with your thumb, but the principle is the same: push one direction to zoom in, and another to zoom out. In rating zoom mechanics, you need to check three things: physical convenience, multi-speed capability, and manual override. Let’s start with convenience.

Which means size and placement. Buttons that are comfortably scaled for my peasant paws are way too big for my wife’s more delicate digits. Make sure that everyone who will use the camera tries the zoom control.

Then there’s button placement. On some cameras, the zoom buttons seem conveniently located until you slide your hand into the camera grip strap and find that you can no longer reach them. And don’t forget working on a tripod. Typically, right-handers configure a tripod with the pan handle on the right side. If the zoom controls are mounted on the (also right-side) hand grip, you’ll have to reach your left hand across the camera to work them, or else never pan and zoom simultaneously.

After physical convenience, the next issue is speed. On better zoom controls, the harder you depress the key, the faster the unit zooms. This allows you to choose slower or faster zoom rates; or you can get really adventurous and start slowly, speed up as the zoom progresses, and then decelerate to a stately finish. Varying zoom rate may seem over-subtle to Getting Starters, but once you’ve seen the effect, you’ll realize it’s an essential skill.

Last but most emphatically not least comes manual zoom: the ability to change focal length by hand. Manual zoom is so desirable that I wouldn’t buy a camera that lacked this vital feature, for three reasons:

Imagine: you’re shooting your toddler as she turns over a rock to discover a millipede wriggling beneath it. Instantly, two things happen: the two-year old equivalent of "waycool!" flits across her face, and, the object of her affection scuttles toward safety. Quick! Zoom in to frame her expression; then pan fast enough to capture the bug before it disappears.

At the magisterial pace of a motor zoom, you’ll never get to telephoto in time for those closeups. With a manual control you can snap the lens from full wide angle to extreme telephoto in a quarter second. Unfortunately, this type of camcorder zoom is a dying breed: almost no consumer camcorders sold today have a manual zoom feature.

Cool Threads, Daddy-o!
With optics and mechanics all checked out, your zoom shopping’s almost done; but don’t forget one last detail: the threads that let you screw filters (and other accessories) onto the front of your lens. Surprisingly, some cameras lack this crucial accessory.

Why crucial? Because even if you think you’ll never use a special effect filter, you should keep a clear glass filter (designated 1A, UV, or skylight) over your lens at all times. These hunks of glass are easy to clean and cheap to replace, unlike your expensive and delicate zoom lens. (The oil on your fingers can permanently etch its optical coatings and seriously degrade its performance.)

And if you do think you’d like to experiment with effects filters, make sure that those threads on the front element of your lens don’t rotate as you zoom and/or focus. That’s because polarizing filters, which do wonders for blue skies and water reflections, change their effect as they are revolved.

Hey, but that’s getting pretty fancy. Next thing you know, you’ll be wanting photographic-grade metal threads instead of the cheesy plastic types fitted on most consumer camcorders.

So that’s the skinny on zoom lenses. Optically, select the speed, range and focal-length spectrum that match your needs. Mechanically, choose buttons your fingers can love, go for variable motor speeds, and insist on manual override.

And don’t forget filter threads. You may not use them right away, but you won’t be a Getting Starter for long, you know.

Good shooting!

Contributing Editor Jim Stinson makes industrial videos, teaches courses in professional video production, and writes video textbooks.