▁the ▁range ▁of ▁F D ▁l enses ▁available ▁sp anned ▁from ▁ 1 5   mm ▁fis he ye ▁to ▁ 3 0 0   mm ▁tele photo , ▁including ▁three ▁zoom ▁l enses . ▁Using ▁manual ▁expos ure ▁and ▁stopped ▁down ▁meter ing , ▁the ▁Can on ▁EF ▁could ▁also ▁be ▁used ▁with ▁the ▁older ▁F L - mount ▁and ▁R - mount ▁l enses . ▁ ▁The ▁EF ▁used ▁a ▁unique ▁sh utter ▁among ▁Can on ' s ▁ 3 5 mm ▁SL R s : ▁a ▁Cop al ▁Square ▁vertical - tra vel ▁metal ▁bla de ▁foc al ▁plane ▁sh utter . ▁ ▁Un us ually ▁long ▁expos ures ▁( from ▁ 1 ▁second ▁to ▁ 3 0 ▁seconds ) ▁were ▁electron ically ▁controlled , ▁while ▁shorter ▁ones ▁( 1 / 1 0 0 0 ▁second ▁to ▁ 1 / 2 ▁second ) ▁were ▁mechan ically ▁controlled . ▁This ▁was ▁very ▁useful ▁in ▁conser ving ▁battery ▁power , ▁and ▁allowed ▁one ▁to ▁use ▁the ▁camera ▁even ▁with ▁dead ▁batter ies . ▁The ▁light ▁meter ing ▁system ' s ▁power ▁switch ▁turned ▁on ▁the ▁meter , ▁removed ▁the ▁lock ▁from ▁the ▁sh utter ▁trigger ▁button ▁and ▁let ▁the ▁film ▁advance ▁lever ▁pop ▁out ▁ 1 5 ▁degrees ▁from ▁the ▁camera ▁body , ▁all ▁in ▁one ▁f lick ▁of ▁the ▁thumb . ▁In ▁the ▁axis ▁of ▁the ▁main ▁switch , ▁a ▁multiple ▁expos ure ▁button ▁is ▁located . ▁Press ing ▁this ▁while ▁co ck ing ▁the ▁sh utter ▁prevents ▁adv ancing ▁the