A jeweler's loupe will usually have markings on it which are designed to indicate the power of magnification it offers. Some are capable of switching between powers, but most simply offer 10 times magnification, making the object of interest 10 times larger under the lens than it is in real life. The higher the power, the lower the depth of field and focal length, meaning that the lens must be placed closer to the object to get a crisp image.
Under a loupe, a jeweler can see things like impurities, blemishes, chips, and inclusions, and the quality of workmanship on a finished piece can also be assessed. With the assistance of a loupe, jewelers can decide how much a piece of jewelry is worth, and they can determine whether or not it is fake, when it was made, and glean other useful information.
”Loupe” is pronounced “loop,” incidentally. The word is believed to come from an Old French word meaning “flawed stone,” although it may also be related to the Old Dutch lupen, “to peer.”
How to Use a Jewelers Loupe
A jeweler's loupe is a specialized magnifying glass used to inspect jewelry. Because magnification and clarity are essential to a good jeweler's loupe, choose a 10x triplet lens loupe to view jewelry and gems. Beginners using loupes shouldn't expect to become experts but should expect to be able to spot basic flaws in gems and jewelry pieces.
1.Purchase a jeweler's loupe. There are quality differences between the pricier and cheaper loupes. The standard loupes for most gemologists have about 20mm lenses (may vary between 18mm to 25mm) in 10 magnification times increase. You also want one that has been corrected for aplanatic and achromatic aberrations to avoid seeing fuzzy or out of focus images.
2 Establish your seeing eye. Hold one finger up and place it about 2 feet before you. Notice what is behind the finger when you look beyond the finger with both eyes. It might be best to look at an object and then look at your finger. Now close one eye at a time while looking at your finger. The eye that places your finger in the same place in relation to the background is your seeing eye.
3. Find a place with as much light as possible. Obviously you are going to need as much light as you can find. Sunlight is the safest bet since florescent and regular light bulbs lack some colors needed. Professionals use light sources such as diamond lamps but in your home, a good desk lamp should do the trick.
4 Place a clean towel on the surface you plan to use. If you are holding a gem such as a diamond and it drops, you want to give it a soft landing spot. This helps to prevent the gem from rolling away if it should drop.
5 Open the loupe until the loupe is straight. This position is the most comfortable one for loupe use.
6 Pick up the loupe with the hand on the same side as your seeing eye.
7 Grasp the loupe between your thumb and middle finger. Place your index finger through the open slot at the bottom of the loupe if it fits there.
8 Place the loupe in front of your eye. Hold it about 1 or 2 inches away from your eye. If the object is too far away from your eye, the item will appear upside down so move the loupe closer to your eye.
9 Steady the loupe in your hand by resting one of your fingers on your cheek.
10 Position the item holding the object so you can steady it by placing it against the other hand.