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Expanding your Horizons: A Buyer's Guide to Lens Adaptors & Converters

Most consumer and prosumer video cameras come with only a permanently-affixed, built-in lens that lets you zoom in and out. While this works in most circumstances, there will be plenty of times when the built-in lens simply isn't enough. For example, if you are shooting an event from the back of a very large room, and you want to zoom in tight to the person speaking, you might find that your camera's zoom lens won't allow you to get close enough to crop out those standing around the speaker. (And do NOT believe digital zoom works in this case! All that does is over-pixilates your image. ) Conversely, you might find yourself shooting in a small space, where, even though you are right against an opposite wall, you can't shoot wide enough to fit in the entire scene. Suppose you wanted to shoot a full moon or perhaps an extreme closeup of the germs in a petri dish. How do you accomplish this and gain the creative control you're looking for as a videographer to get the shots you need? By using lens accessories, such as adaptors and converters.

So what are lens adaptors and converters? Adaptors come in a number of forms, but the most common are external lenses (or converters) for your camera, designed to optically convert the image by increasing or decreasing the focal length of your camera's built-in lens. Focal length - what's that? It is the distance from where your lens focuses the light entering it to the camera's charge-coupled devices. This, in turn, determines width of the lens' field of view. In layman's terms, short focal length = a wide field of view or a wide angle (zooming out), and long focal length = a narrow field of view or telephoto angle (zoomed in). (See this month's Basic Training for more on how to use lenses and adapters.)

If you look at the front of your camcorder lens, you should see either some threads that allow you to screw on your accessories or something resembling a tongue-and-groove (also known as a bayonet mount). This is where you will mount your accessories in front of your lens. These mounts come in many different sizes and are measured in millimeters (or mm). You need to know the exact size of the mount to purchase the right adaptor for your camera model. The correct size should be on the camera itself. If not, consult your owner's manual.

Let's say you add a 2x converter to your camera. You have just doubled your camera's focal length, allowing you to zoom in twice as close to your subject as your camera's built-in lens will allow. A 3x converter allows you to zoom in three times closer, and so on. Smaller-number lens converters work the opposite way. A .5x converter, for example, cuts your focal length in half, giving you a wider angle. You can now zoom out further than you could with the built-in camera lens. For an extreme wide-angle look, try a fish-eye converter like the lens for skateboarding videos from Demon.

Prices for lens converters run the gamut from around $50 for a Varizoom or Demon to over $4000 for models from RedRock and Century Optics.

You certainly get what you pay for, but consider these factors when choosing a converter:

• The Type of Optics: Converters can be made of either glass or plastic. Plastic is often thinner, stronger and lighter than glass optics. However, glass optics are always better, because the glass used in them is ground to very fine specifications and is more resistant to scratches, thus yielding better images.
• Lens Coatings: Lenses have coatings of chemicals designed to keep diffraction at a minimum. Diffraction is a phenomenon that occurs inside a lens when light passing through it is bent. In short, it can distort your image. The best converters are multi-coated, meaning they are coated with chemicals more than once. Coating reduces the distortion effect. Multi-coated lenses are better than lenses coated only once, and these are better than lenses not coated at all.
  Additionally, the number of optics in a converter can affect the price. Generally, the more optics in a converter, the better, because a single lens tends to magnify or reduce parts of images, especially around the edges of the lens. A second lens combines with the first to correct the distortion. A third lens combines with the second and reduces distortion even more, and so on.
• Zoom-Through: Finally, a fourth consideration affecting the price of converters is whether or not the converter is zoom-through or not. This means you can zoom in or out all the way through the converter (in either direction) without losing your focus.

For each feature, the price goes up. Century Precision Optics, Demon, Panasonic and others make good-quality mid-price range converters in the $200-$1000 range that take into account these concerns and still give you good video images at an affordable price.