Technical Glossary

Macro photography is the reproduction of small objects from a magnification ratio of approx. 1:4 up to about 5:1 (at which point  microphotography begins). Tamron´s prime macro lenses are:

Di Lenses (full format)
SP AF 90mm F/2,8 Di MACRO 1:1
SP AF 180mm F/3,5 Di LD[ IF] MACRO 1:1

Di II Lenses (APS-C format)
SP AF60mm F/2.0 Di II LD [ IF] Macro 1:1

A magnification ratio is expressed in 1:x, which is a ratio of the actual size of a subject, "1", to the size of the subject image reproduced on the film plane, "1/x". Therefore, the larger the x value becomes, the smaller the reproduced image on the film plane becomes. For example, an image of a coin reproduced on film as the same size as the actual coin is 1:1 macro, while the same image reproduced at 1/2 of the original size is 1:2 macro. The macro ratio is also referred to as magnification ratio, and the maximum ratio of a lens' reproduction capability is designated as "maximum magnification ratio".

^{1 : 4 (0.25X)}

^{1 : 2 (0.5X)}

^{1 : 1 (1X)}

The luminosity is defined by the maximum effective diaphragm opening divided by the focal length of a lens.

^{Typical diaphragm}

Lenses with wide apertures are especially required under unfavorable lighting conditions (interiors without flash, animal photography in the dusk etc.). In addition, fast lenses offer a wider scope of creative potential.
Because the size of the diaphragm opening determines the depth of field, conscious and pleasantly blurred backgrounds can be generated with big diaphragm openings, creating dramatic effects by softening surrounding details so the subject seems to “pop” off the background. As a rule stopped-down fast lenses deliver better results than slower lenses at the same aperture setting.

The minimum focusing distance is the distance between the object and the film plane or the image sensor of the camera at which a lens still illustrates sharply. The minimum focusing distance together with the focal length determines the magnification ratio.