Magnifiers come in all shapes and types. They are often classified based on their power, lens type, and design purpose. Magnifiers can be either optical or video based. Some examples of optical magnifiers are hand-held magnifiers, stand magnifiers, spectacles, and telescopic devices. Video magnifiers use camcorder-like cameras and certain video magnifiers are hand-held, certain others resemble a computer, and a few others are head-mounted. All the magnifiers are designed for distinct applications and come with different benefits.
Here are some categories of magnifiers:
Contents
Power
You can classify the magnifiers according to their power, which is measured in several ways. The most common method is times magnification or power. It refers to how much bigger an object will appear when viewed through the magnifier as compared to when viewed with the naked eye. The symbol “X” is used to indicate the manufacturer’s representation of the power provided by a particular magnifier.
Diopter
A popular term used to refer to the magnifying power of a device; a diopter is a metric measurement of the lens power. It is commonly used as a unit of measurement by your ophthalmologist while prescribing eyeglasses or contact lenses. Likewise, the power of a hand-held, stand and magnifying spectacles can be measured or represented in diopters or times magnification. Even though the ’X’ power measurements vary from manufacturer to manufacturer, diopters do NOT vary. Optical magnifications are available in power ranges from 1x to 10x. Video magnifiers fall in the range of 5x to as much as 60x magnification.
Designs
Magnifiers can be classified according to their designs as well. They can be:
Hand-held magnifiers – ideal for short-term spotting tasks of near objects such as reading menus, price tags, and pill bottles. They are portable, versatile, and economical, and usually, come with or without light sources.
Stand magnifiers – these are ideal for extended viewing tasks of near objects such as reading. Stand magnifiers are placed directly on the object and come with or without illumination.
Magnifying spectacles – these are specifically designed for hands-free viewing of near objects for an extended period.
Telescopic devices are primarily designed to magnify distant objects. These magnifiers can be hand-held for short-term spotting and worn as eyewear for extended periods – for example, watching television.
Electronic Video Magnifiers – these magnifiers offer the highest level of magnification and offer the best contrast of objects being viewed. They can be hand-held, head-mounted, or in a desktop design.
Apart from these, there is a multitude of designs to help people with low vision accomplish various types of tasks. Low-vision devices and magnifiers in particular are essential tools for people with low vision.
Different Types of Lenses:
- Biconvex lens
- Aspheric Lens
- Aplanatic Lens
- Achromatic Lens
Choosing a Magnifier
When choosing a magnifier, the first thing to bear in mind is the purpose – for instance, what is the use of the magnifier – reading a book, reading medicine labels, or watching television. Once you have identified the need, the next step is to determine the duration of viewing and the distance of viewing. These two factors determine the level of magnification required.
Distance
Distance is the space between the viewer and the object that is to be seen and determined the type of magnifier design required. Distance is categorised as:
Near tasks – such as reading distance (usually 20″ or closer) which includes tasks such as reading, writing, and eating.
Intermediate tasks refer to tasks at about arm’s length (20″ – to 40″) and include activities such as viewing a computer monitor, reading sheet music, playing cards, and other hobbies and handicrafts.
Distance tasks involve any visual task that is not near or intermediate (usually 6′ or more). These include activities such as watching television, reading indoor and outdoor signs, and watching sporting events among others.
Duration
It refers to the time for which you will use a magnifier to accomplish a given task. They can be categorised as:
Short-term spotting tasks that happen for a maximum of only a few minutes at a time. Examples include reading menus, price tags, and street signs, and writing return addresses on envelopes.
Extended viewing tasks happen over a longer period. It could be tasks like reading books, newspapers, and magazines, watching television, and writing letters at home.
In short, distance and duration help to identify the visual goal, and to easily narrow the range of devices best suited. The required magnifying power, need or desire for illumination, and other factors can be used as additional pointers to choose from the available options.
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