Autofocus macro lens. The lens is also a fine short tele/portrait lens, with a field of view equivalent to 96mm* when used on a PENTAX 645D or 77mm* when used on a film 645 camera (*in the 24×36 format). This Macro lens features SMC (super multi coating) that significantly increase the amount of light transmitted by the lens. It also focuses as close as 39cm to achieve 1:1 magnification ratio

for more info please click : http://www.ricoh-imaging.co.uk/en/645-mount/smc-FA-645-120mm-F-4-0-macro.html