If you’re one of the more than 3 million Americans over the age of 40 who suffer from low vision, you already know how difficult it can be to deal with compromised sight. Even if your vision impairment is the natural result of aging, the last thing you want to worry about is buying a magnifying aid, only to discover that it doesn’t live up to its promises.
When purchasing a magnifier, there are three important points you should keep in mind to avoid choosing the wrong one, and to prevent the possibility of falling victim to the exaggerated, and often blatantly false claims, that are made by many magnifying glass companies.
A higher magnification is not always superior to a lower magnification
A larger lens is not always better than a smaller lens
Many magnifiers actually provide far lower magnifications than they claim
As a group, these factors revolve around one crucial optical rule: the bigger the magnifying lens, the smaller the magnification.
The Implication of Magnification
One of the most common mistakes made by consumers when shopping for a magnifying glass is to assume that the higher its power, the more effective a tool it will be. This is not always the case however, especially where an activity like reading is concerned.
A magnifier is a clear, convex lens that causes light rays to bend and converge, and objects to appear larger than they are as a result. For example:
a 2X magnifying glass makes items look twice as big as they are
a 20X jeweler’s loupe magnifier makes those same items look 20 times as big as they are
But because of the physics surrounding light rays and the curvature of the convex lens, the 20X magnifier has to be significantly smaller than the 2X magnifying lens in order to work effectively. This means that it’s only capable of focusing on a relatively small viewing area.
You wouldn’t make much reading progress moving across the printed page of your favorite book or newspaper with a high-powered magnifying lens, since you’d typically only be able to view a few letters at a time.
The Multi-Purpose Myth
The other common assumption about magnifiers is that a bigger lens is more versatile, and therefore represents a more worthwhile purchase. After all, a larger magnifying glass allows you to see more of what you’re looking at, and is often easier and more convenient to handle. But while bigger is often better in the case of something like a reading magnifier, since it means you can scan a whole page or paragraph at once, a larger lens also requires a sacrifice in magnification.
The laws of optics tell us:
the higher the power, the smaller the magnifying lens must be
the bigger the magnifying glass, the lower its magnification
In the world of low-cost magnifiers, a lens with a width of 4 inches will always have a lower magnification than one that’s only 1 inch across. A large magnifying glass simply cannot pull double duty as a jeweler’s loupe, or any other type of high-power, fine-detail magnifier.
Unveiling the Imposters
Many magnifying glasses sold today are not at all what they claim to be. Fortunately, once you understand the relationship between a magnifier’s size and its power, you’re far less likely to be fooled by unethical companies making unrealistic promises about their magnifying aids.
Remember that it’s not physically possible to produce a magnifying glass that’s a single lens, lightweight, inexpensive, and that incorporates both:
a wide field of view, and
a high power of magnification
While the most commonly seen false claims involve declarations of 5X and 10X magnification, for lenses that actually offer no more than 2X or 3X power, there are many examples of far more exaggerated statements in the market today. You won’t have to look far in fact, to find inexpensive products that claim to offer 20X, or even 30X magnification, with lenses that are as large as 4 - 6 inches across.
The best way to avoid being taken advantage of when buying a magnifying glass is to use your common sense, and to limit your dealings to reputable companies. It may sound cliché, but if you run across a magnifier that appears to be claiming an inflated magnification for its size, remember that some things simply are too good to be true.