This magnifier is not a typical refractive lens that most folks are familiar with and yet it brings clarity to minute detail. It is an opaque card with a “pin hole” in the center. I have used many different materials for construction but one of the most expedient materials is duct tape. You can fold a piece of duct tape over on it’s self to make a small two inch square then take a pin and poke a hole in the middle.
The purpose of viewing through the tiny hole is that it reduces the pin-points of light known as “circles of confusion”. A large hole allows numerous “circles” of light that contribute to dispersion/interference of the image that make it look fuzzy whereas a small hole allows fewer “circles” that bring more clarity by eliminating the fuzz factor of overlapping points of light.
When viewing an object, hold the card just in front of your eye, then bring the object for viewing up close until it comes into focus. You would be amazed at the detail that can be seen on a coin, postage stamp, wristwatch, your finger prints, or more practically, medicine bottle labels and instructions. When possible, view your object in good light. This also helps your iris to constrict, thus enabling better focus as well.
On one occasion I made a wallet pocket magnifier that consisted of a plastic credit card sized piece from a coffee can lid with a single hole punched through it. It came in handy when I needed to read a serial number off of a water heater in a closet. In the tight and somewhat dark quarters, I was able to read the number without a flashlight or reading glasses.
When you have a little spare time, make one for yourself and discover it’s amazing ability for yourself.