▁well ▁as ▁an ▁a pert ure ▁ring , ▁it ▁is ▁relatively ▁large ▁and ▁heavy , ▁and ▁it ▁is ▁not ▁water ▁or ▁dust ▁proof . ▁ ▁The ▁anti - reflect ive ▁co ating ▁of ▁the ▁tele photo ▁l ens ▁with ▁ 1 . 7 ▁times ▁normal ▁foc al ▁length ▁has ▁ 1 4 ▁l enses ▁in ▁ 1 1 ▁groups , ▁two ▁of ▁them ▁as pher ic ▁and ▁another ▁with ▁extremely ▁low ▁disp ersion . ▁The ▁front ▁l ens ▁is ▁made ▁of ▁extremely ▁high ▁ref ract ing ▁glass . ▁The ▁No ctic ron ▁has ▁an ▁excellent ▁image ▁quality . ▁ ▁The ▁No ctic ron ▁l enses ▁allow ▁a ▁fast ▁l ens - body ▁communication ▁for ▁aut of oc uss ing ▁with ▁its ▁rather ▁silent ▁ste pper ▁motor , ▁due ▁to ▁the ▁large ▁a pert ure ▁size ▁also ▁at ▁low ▁light ▁conditions . ▁ ▁Image ▁stabil isation ▁ ▁As ▁of ▁late ▁ 2 0 1 7 , ▁while ▁there ▁are ▁other ▁f / 1 . 2 ▁Micro ▁Four ▁Third s ▁aut of ocus ▁l enses , ▁it ▁is ▁still ▁the ▁fast est ▁Micro ▁Four ▁Third s ▁l ens ▁with ▁both ▁image ▁stabil isation ▁and ▁aut of ocus . ▁ ▁The ▁optical ▁image ▁stabil isation ▁of ▁the ▁l ens ▁can ▁even ▁be ▁combined ▁with ▁the ▁opt o - me chan ical ▁image ▁stabil isation ▁systems ▁of ▁some ▁camera ▁bodies ▁of ▁the ▁system ▁( D ual ▁Image ▁St abil isation ▁= ▁D ual ▁I . S .). ▁The ▁‘ ’ D ual ▁I . S .’ ’