The magnification of a magnifier depends on where it is placed between the user's eye and the object being viewed, as well as the total distance between the eye and the object. Magnifiers are typically described in terms of their magnifying power. The magnifying power is the ratio of the sizes of the images formed with and without the magnifier at a distance of 0.25 meters from the eye. The highest magnification is obtained by putting the magnifier very close to the eye and moving the object to be magnified to obtain the best focus. The object will usually end up very close to the magnifier. Magnifiers are not always used this way. Some people find it more comfortable to put the magnifier close to the object to be magnified and move their head until a good image is obtained.
The process of magnification inherently creates a distorted image and a loss of light. This phenomena becomes more apparent the higher the power of magnification. Many magnifiers are designed as triplets, three lenses cemented together to reduce the distortive & light loss effects. The coddington is another effective design. The coddington magnifier is created from a single piece of precision ground glass. The equator of the glass piece has a groove in it, which reduces the destortive effects of magnification. Due to the groove in the equator of the glass, the coddington design is heavier and larger than a triplet of the same viewing diameter.
Coin magnifiers and loupes can be utilized to closely examine and evaluate your coins, helping you to grade and determine their value. Magnifiers allow you to investigate the mintmarks, scratches and numismatic details of your coins. Some magnifiers offer up to 3 different powers of magnification. Many magnifiers fold into themselves to help protect the lense from scratches and dirt.