2 8 mm , ▁ 3 5 mm , ▁ 4 0 mm , ▁ 5 0 mm , ▁ 8 5 mm , ▁ 1 0 5 mm , ▁ 1 3 5 mm , ▁ 2 0 0 mm , ▁ 3 0 0 mm , ▁ 4 0 0 mm , ▁and ▁ 6 0 0 mm . ▁For ▁these ▁lengths ▁many ▁manufact ur ers ▁produce ▁two ▁or ▁more ▁l enses ▁with ▁the ▁same ▁foc al ▁length ▁but ▁with ▁different ▁maximum ▁a pert ures ▁to ▁suit ▁the ▁different ▁needs ▁of ▁photograph ers . ▁ ▁Add itional ▁foc al ▁lengths ▁can ▁be ▁created ▁by ▁using ▁a ▁tele con verter . ▁ ▁For ▁ 3 5 ▁mm ▁film ▁and ▁full ▁frame ▁digital ▁cam eras ▁( in ▁which ▁the ▁image ▁area ▁is ▁ 3 6 ▁by ▁ 2 4 ▁mill im eters ) ▁prime ▁l enses ▁can ▁be ▁categor ized ▁by ▁foc al ▁length ▁as ▁follows : ▁▁▁ 1 2 ▁to ▁ 2 1 ▁mm : ▁Ult ra - W ide ▁— ▁usually ▁used ▁at ▁very ▁close ▁subject ▁distances ▁to ▁produce ▁a ▁perspective ▁that ▁provides ▁a ▁dram atic , ▁often ▁extreme ▁image ▁that ▁dist ort s ▁a ▁scene ’ s ▁natural ▁proport ions ▁▁ 2 4 ▁to ▁ 3 5 ▁mm : ▁W ide ▁— ▁capture ▁a ▁wider ▁field ▁of ▁view ▁than ▁a ▁standard ▁l ens , ▁at ▁shorter ▁distances , ▁the ▁perspective ▁can ▁show ▁dist ort ion ▁▁ 5 0 ▁mm : ▁Standard ▁— ▁a ▁foc al ▁length ▁near ▁the ▁ 4