Guide to Camcorder Lenses

Chances are you don't pay much attention to a camcorder's lens other than how much zoom it packs. The lens is integral to how your camcorder functions. There are two basic types of camcorder lenses: those that are built into a camcorder and accessory lenses that you buy after the fact and attach for specific effects.

Optical Zoom Lenses

A camcorder with an optical zoom lens can magnify far away objects. It does this by moving pieces of glass within the camcorder. Optical zoom lenses are distinguished by how much magnification they offer. A 10x zoom lens can magnify an object 10 times.

Fixed-Focus Lenses

A fixed focus lens is one that doesn't move to achieve magnification. It is fixed in place. Many camcorders with a fixed focus lens nonetheless offer a digital zoom. Unlike its optical counterpart, a digital zoom doesn't magnify a faraway object. It crops the scene to focus on one particular subject. For that reason, a digital zoom usually provides images of lower quality than an optical zoom lens.

Understanding Focal Lengths

The focal length of a lens refers to the distance from the center of the lens to the point on the image sensor where the image is in focus. In practical terms, the focal length tells you how much zoom your camcorder offers and what angles it captures.

Focal lengths are measured in millimeters. For camcorders with optical zoom lenses, you see a pair of numbers. The first gives you the focal length at the wide-angle, and the second is the maximum focal length at telephoto, which is when you've zoomed out or magnified a subject. You can determine the magnification, or "x" factor of your camcorder, by dividing the second number in the focal length by the first. So a camcorder with a 35mm-350mm lens has a 10x optical zoom.

Wide-Angle Lenses

A growing number of camcorders tout wide-angle lenses. There's no hard and fast rule for when a built-in camcorder lens is considered wide-angle, but you typically see a model advertised as such when it has a focal length below 39mm. Like the name implies, a wide-angle lens captures more of a scene without the shooter having to take a step or two back to take it all in.

Understanding Aperture

A lens regulates the amount of light passing through to the sensor using a diaphragm, also called the iris. Think of a pupil widening to let in more light or constricting to let in less light, and you'll get an idea of how the iris functions.

The size of the iris opening is called the aperture. Sophisticated cameras let you control the size of the aperture. This is important for two reasons:

• A wide aperture lets in more light, brightening the scene and improving performance in dimly lit environments. Conversely, a small aperture lets in less light.
• Adjusting the lens aperture lets you adjust the depth of field, which is how much of a scene is in focus. A wide aperture makes objects in front of you well-focused but the background blurry. A small aperture puts everything into focus.

Camcorder makers usually advertise the maximum aperture or how wide the iris can open to admit light. The wider, the better.

How Can You Tell What Your Camcorder's Aperture Is?

A camcorder's aperture is measured in f-stops. Like the optical zoom rating, you can do some math to determine the maximum aperture of your camcorder. Divide the total focal length by the diameter of the lens, which is typically etched into the bottom of the lens barrel. So, if you have a 220mm lens with a diameter of 55mm, you have a maximum aperture of f/4.

The lower the f-stop number, the wider the lens aperture. So unlike with an optical zoom, where you're looking for a high number, you want a camcorder with a low aperture or f-stop number.