There are two ways the magnification of the lens is generally described.
- The ratio form gives the ratio of image size to object size. In other words, if a lens has a maximum magnification of 1:4, then at that magnification the object will be 4 times larger than the image.
- The decimal form is simply the decimal representation of that ratio. For example, a 1:4 magnification can also be expressed as 0.25x.
To convert from the ratio form to the decimal form, divide the object size by the image size.
Some Common Magnifications
- 5:1 (5x) – The highest magnification of the Canon MP-E 65mm f/2.8
- 1:1 (1x) – True macro magnification, the image is the same size as the subject was. Most true macro lens support this magnification.
- 1:2 (0.5x) – Half macro magnification, the Canon EF 50mm f/2.5 compact macro and the Zeiss Macro Planar lenses reach this.
- 1:4 (0.25x) – “Consumer Macro”, most lenses that aren’t dedicated macro lenses but are branded as macro reach this magnification.