linear magnification

In optics, linear magnification refers to the ratio of an image's size to the size of the object that created it, measured perpendicularly to the optical axis. A negative linear magnification indicates an inverted image.1

There are other types of magnification:
* Longitudinal magnification: This measures how much an image increases in size along the optical axis. It is equal to the square of the lateral magnification, meaning it's always positive. This is why microscopes, which have high lateral magnification, have a very small depth of field.12
* Angular magnification: This is used with instruments like magnifiers and binoculars and is the ratio of the angles subtended by the image and the object.1

While there's no theoretical limit to magnification, practical limits are set by an optical system's ability to distinguish between closely spaced objects, known as its resolving power.1