When you look at the variety of augmentation products on offer, you may find the terms used for augmentation a bit confusing. Here we briefly show what each measure consists of and how to calculate one from the other.

For brevity we will use the following abbreviations:

• Focal Length – FL
• Magnifying Power – MP
• Total magnifying power – TP

Focal Length (FL)

The FL of a lens is the distance where parallel light beams coming from one side will converge to a point on the other. The shorter the focal length, the higher the magnification of the lens.

• From FL (in inches) to diopter: Divide the number 39.37 by the focal length.
• FL (in inches) to MP: Divide the number 9.84 by FL (in inches).
• FL (in inches) to TP: Divide the number 9.84 by FL (in inches), then add 1 to the result.

Diopter

Diopter is less often written as diopter and the higher the value, the more magnification the lens has.

• Diopter to FL (in inches) – Divide 39.37 by diopter.
• Diopter to MP: Divide the diopter by 4.
• Diopter to TP: Divide the diopter by 4, then add 1.

Magnification Power (MP)

It is a number usually followed by an ‘x’ that shows how much larger an object looks when viewed through a magnifying glass. Although this is called ‘magnification power’, it is often confused with ‘full magnification power’, the definition of that follows. So if you see a lens product rated as 2x, it’s usually its full power and not its magnification power. If an object appears 100% larger, the MP of the lens will be given as 1x.

• From MP to FL (in inches) – Divide the number 9.84 by MP.
• From MP to Diopter – Multiply by 4.
• From MP to TP: just add 1.

Total power of increase or total power (TP)

This is the most used way to describe the increase between that MP and the previous one. It’s just MP + 1. The reason this term is used more often is because it’s easier to understand, but many people confuse one with the other. If a 5-inch-wide object is viewed through a lens and appears as a 10-inch-wide object, then the total power of the lens is 2x.

• TP to FL (in inches): Subtract 1 from TP, then divide the number 9.84 by the result.
• From TP to diopter: Subtract 1 from the TP, then multiply the result by 4.
• From TP to MP – Only subtract 1.