Magnification is usually expressed as a fraction delimited by a colon with the first number indicating the height of the image, and the second the height of the object. Thus 1:1 indicates life-size replication; 1:3 that the object is projected at 1/3 size onto film/sensor; and 5:1 that the height of the image is 5 times real-life -sized.
Technically, the formula for computing magnification is:
In this formula:
- M is the ensuing magnification
- d is the distance from the lens to the image/object (subscript i or o)
- h is the height of the image/object (subscript i or o)
- f is the focal length
N.B! Considering that the ‘lens’ in physical terms is not a single point, computation of magnification based on known lens traits (focal length, MFD, lens size) is not obvious.« Back to Glossary Index