Magnifiers are useful in any situation where small objects or letters need to be viewed. But not all magnifiers are created equal, and in fact without some guidance you may end up with the wrong magnifiers for the job. This guide aims to help you select the proper magnifier for your needs.
PROPERTIES OF MAGNIFIERS
All magnifiers will magnify small objects, but they will vary widely in how they do the jobs. These are some properties of magnifiers you should look for:
POWER (or Magnification): This is how much larger a magnifier makes things. A 2X magnifier makes things 2 times as large, a 5X magnifier will make thing five times larger, and so on. Don’t be seduced by high listed magnification, for one thing we’ve already covered how magnifier manufacturers lie and higher magnification will also effect other specifications, such as:
WORKING DISTANCE: This is a measure of how far you have to have the magnifier from the object being viewed as well as how close your eye should be to the lens. At low powers the working is going to be several inches, but as power increases it drops quickly. By the time you have a 10X magnifier the working distance is less than an inch.
FIELD OF VIEW: This is the total area a magnifier can view. Once again, as power increases this figure decreases. A 2x magnifier can view several inches of area, but by the time you reach 5x it will be only about an inch-and a half. At 10x you will be viewing an area less than half an inch across!
LENS SIZE: This is related to field of view in that the larger the lens the more field of view you will have. But to get higher magnifications you must use smaller and smaller lenses. A 2x lens can be as large as 6″ (and we’ve seen bigger!) but a 10X lens will need to be very small, less than 3/4″ is typical.
All of these features are fundamental laws of optics. You simply cannot get around them. A 10x magnifier cannot be 4″ across and held 12″ away from the subject matter. Its not going to happen!
There are many other characteristics of magnifiers but they are mostly related to the above specifications. Instead we will concentrate on the different styles of magnifiers
TYPES OF MAGNIFIERS
and the most common design is a classic hand-held magnifier. These are usually large, single lenses (2-5″ across is typical) that are low power and are mostly for reading text or examining small objects. This is the design most people are familiar with when they think of magnifiers. There will be many variations of design and size, as well as features such as illumination or fancy materials (brass is common and attractive). There are too many variations to go in here so we will simply say that most of these magnifiers go from 2x to 5x, with the emphasis at the lower part of the magnification scale
Inspection magnifiers are for closer work on small objects that need high power to be viewed or measured. Inspection magnifiers are higher powered than reading magnifier (4x-10x is common)and may have features such as illumination, measuring reticles, and many differing designs.
Loupes are meant for very close inspection of small objects – in particular jewelry or electronics. They are hand-held or held in the eye by squinting. Loupes tend to be higher powered (7x-12x is typical). The sizes of Loupes, as a result, tend to be small and are meant to be used almost right next to the object being viewed.
Once your get above 12x the line between magnifier and microscope gets blurred. Very-high magnifiers tend to be very small, very expensive, and sometimes the job can be done more effectively by a portable microscope instead. The magnifications of inspection microscopes (10x-40x) should also be considered when magnifier manufacturers make claims of excessive magnification.
So with this knowledge in mind, we can think of all magnifiers with the same magnification as being pretty much identical? WRONG! Every magnifier is going to have different levels of quality depending on the design.
The biggest issue with magnifiers is edge distortion. Looking through the center of most magnifiers will usually give you a clean image, but as you get near the edge there may be problems with distortion – if you were looking at a piece of graph paper, for example, the lines near the edge of the lens would bend and curve in a poorly designed lens.
With low-power lenses just having a properly designed lens is enough to avoid distortion. But with higher powers it is often the case where you need more than one lens to get the power and the clean image. Doublets, Triplets, and in some cases Quadruplet lenses are used to make a clean edge. More lenses, of course, means more work on the design and construction and so more cost.
Other quality factors come into play at higher magnification designs: lens coatings allow much more light to transmit through the lens and reduce and glare that might come from other light sources. These can also be useful for certain hand-held magnifiers as well, but are not as common.
Coming up in Part 2 – So what’s the best magnifier for me?