From Manufacturer
Currently the lightest and most compact 180mm macro lens on the market, this lens will provide 1:1 magnification, and the two LD elements included in the design of the lens make sure you get the sharpest quality possible.
An excellent lens for close-up work in the field.
1:1 Magnification
Allows for life-size image on the negative or slide; at a distance of 18.5" (47 cm)
Internal Focus
The lens neither extends nor contracts physically when focusing; all moving elements are contained within the lens barrel
Di
Digitally Integrated lenses are designed to meet the performance characteristics of digital SLR cameras
FEC
Filter Effect Control is designed to rotate the filter to the desired position even with the hood attached. This is accomplished by rotating the FEC ring that in turn rotates the portion of the lens where the filter is mounted