What is a Jewelers Loupe?
Put succinctly, a jewelers loupe is basically a type of magnifying glass. These magnifying aids, which are also know as "lupes" are most frequently used by jewelers to assess the quality of jewelry, watch mechanisms and gemstones. Loupes make the perception of impurities, flaws and imperfections very easy. Jewelers use their magnifiers to establish the value of pieces of jewelry and even to determine whether something is a fake.
The original of the word "loupe" is not certain. There are two stories. Firstly, it is believed to stem from an old word of French word that means "flawed stone". Secondly, and equally possibly, "loupe" could come from the Old Dutch verb Lupen, which means "to peer."
So, now we know where the odd name comes from, but what other uses do they have? Surely they are not the sole property of jewelleing elite?!
Well, in addition to the use in the world of gemstones, there are plenty of other uses. They are commonly used in the fields of botany to examine plants, geology to study rock-forms and entomology to scrutinize insects & in vertebrae. Less scientifically, they are used to examine print quality and philatelists use loupes to get a close look at their stamps.
There are many variants on the basic jeweler's loupe design template. Some come with in-built illumination and others do not. The principle criterion is magnification - and there are three levels; 10X, 20X and 30X. 10X allows the user to see the object he/she is observing through the loupe ten times larger than in real life. 20X renders objects 20 times larger and 30X makes things 30 times as big. Other levels of magnification exist, but these are the industry standard. The higher the level of magnification, the lower the depth of field and focal length, which means that the lens of the loupe must be positioned closer to the object to get an undistorted image.
The most important part of the loupe is its lens. Lenses are ground from either plastic or glass. Glass offers superior performance and is used in high quality units. A good loupe will also have more than one lens, because a single magnifying lens can cause image distortion. Loupes with three lenses (known as Triplet) are common for this very reason. Aplanatic lenses are used in the very best units. Aplanatic lenses are free from spherical aberration, thus offering the highest quality magnification.
