If you’ve looked at digital cameras lately you’ve probably noticed a lot of terminology and numbers associated with the zoom lens capability. If you’re going to make a good choice on a new camera purchase or get the best out of your current camera, you need to understand what all that jargon means. This article is your guide to zoom technology.
Zoom Lens, Definition
From Dictionary.com: “a lens assembly whose focal length can be continuously adjusted to provide various degrees of magnification without any loss of focus”. What does that mean in practical terms? Using a zoom lens, you can make a given object appear larger or smaller in your viewfinder/screen by zooming in (larger) or out (smaller). Want to get your whole family in the picture at the reunion but can’t step back any more? Zoom out! Taking a picture of the polar bear at the zoo and can’t get any closer? Zoom in! Very handy indeed.
Focal Length
This is a measurement of the focusing ability of a given lens. Since you’ll be concerned with comparing different cameras using the 35mm Equivalent (see below), just remember these three general ranges:
Wide angle: 35mm or less. The smaller the focal length, the wider the angle of view of the lens. The wide angle gets more of the scene into the picture and makes the subject seem farther away. This is very useful for landscapes, group shots and tight spaces.
Normal: between wide angle and telephoto, with 50mm as the standard. This approximates what the human eye sees and is suitable for most kinds of photography.
Telephoto: 80mm or more. The larger the focal length, the more powerful the magnification of the lens. The telephoto gets less of the scene into the picture and makes the subject seem closer. Best uses for telephoto lenses are portraits, animals, and situations where you can’t get any closer to the subject.
35mm Equivalent
Digital cameras have sensors that do the actual work of capturing the image. Some cameras have smaller sensors, and some have larger sensors. Since the image magnification delivered by a lens of a given focal length depends on the size of the sensor, looking at the focal length range of the zoom lens alone is not very useful. Manufacturers avoid this confusion by providing the 35mm equivalent, which relates the performance of the lens to 35mm film camera standards. You can compare the performance of two different cameras’ zoom lenses using the 35mm Equivalent.
The X Factor
Often, what you’ll see on a package is something like “10X Optical Zoom”. Simply put, this is the ratio of the longest focal length of the lens to the shortest focal length of the lens. For example, if the longest focal length is 175mm and the shortest focal length is 35mm, then the X factor of that lens would be 5X. The larger the X factor, the greater the difference between the highest and lowest magnification of the lens.
Optical Zoom
Optical Zoom means that your lens is changing its focal length by moving lens elements around. Usually the optical zoom is rated with an X Factor and described with a 35mm Equivalent range, such as 3X, 35mm – 105mm. Optical zooms are carefully designed to preserve your image quality throughout the entire zoom range, so be sure to select a range that will meet your needs.
Digital Zoom
This has nothing to do with your camera’s lens. It’s a software function of the camera that increases the apparent magnification of the image by using only a part of your camera’s sensor. Using the digital zoom drastically degrades your image quality, however, so it’s best to avoid it. Some cameras only offer digital zoom; I don’t recommend them. Digital zoom is usually described by an X Factor.
Trade Offs
There’s no such thing as a free lunch, right? Cameras with larger optical zoom ranges (as high as 35X at this point in time) are bigger and heavier than cameras with more modest zooms. Very compact cameras typically have smaller optical zoom ranges (under 5X). Generally, more optical zoom range also means a higher price point within a given size class of camera.
How do You Choose?
Choosing a camera that fits your needs involves far more than the zoom lens, of course. That said, if you are mostly taking snapshots of family and friends, a modest zoom with a range of 5X or less will probably be fine. If you shoot a lot of landscapes and scenery, you might want the lower number on your 35mm Equivalent range to be 28mm or 24mm. If you want to take pictures of sports or wildlife, you’ll probably want a wider zoom range (10X or more) and the higher number on your 35mm Equivalent range to be 200mm or more… the higher the better.
I hope you’ve found this article useful! Best of luck in your photography, and look for more articles in my Camera Basics series.