▁estimate ▁along ▁the ▁scale . ▁The ▁expos ure ▁scale ▁also ▁has ▁a ▁stopped ▁down ▁meter ing ▁mark , ▁where ▁the ▁need le ▁should ▁be ▁aligned ▁when ▁using ▁stopped ▁down ▁meter ing . ▁Due ▁to ▁corre ctions ▁taken ▁for ▁proper ▁expos ure ▁with ▁full ▁a pert ure ▁meter ing , ▁stopped ▁down ▁meter ing ▁with ▁larger ▁a pert ures ▁than ▁f / 2 . 8 ▁was ▁not ▁reliable . ▁ ▁Power ing ▁the ▁electro - me chan ical ▁sh utter ▁and ▁light ▁meter ▁were ▁two ▁P X ▁ 6 2 5 ▁ 1 . 3 5 ▁volt ▁mer cur y ▁batter ies , ▁but ▁the ▁camera ▁has ▁a ▁voltage ▁reg ulator ▁which ▁allows ▁the ▁use ▁of ▁ 1 . 5 ▁volt ▁batter ies . ▁The ▁EF ▁is ▁the ▁only ▁camera ▁in ▁the ▁manual ▁focus ▁Can on ▁line ▁of ▁the ▁ 1 9 6 0 s ▁and ▁ 1 9 7 0 s ▁( which ▁includes ▁the ▁F T b , ▁the ▁F - 1 , ▁and ▁the ▁F T ) ▁that ▁can ▁be ▁used ▁with ▁common ▁ 1 . 5 ▁volt ▁batter ies ▁without ▁modification ▁to ▁the ▁internal ▁electron ics . ▁▁ ▁Like ▁all ▁pre - 1 9 8 7 ▁Can on ▁SL R ' s , ▁the ▁EF ▁accepted ▁Can on ▁F D ▁mount ▁l enses . ▁ ▁The ▁sh utter ▁speed ▁range ▁was ▁ 1 / 1 0 0 0 ▁of ▁a ▁second ▁to ▁ 3 0 ▁seconds ▁( the ▁ 1 5 ▁& ▁ 3 0 ▁second ▁settings ▁actually ▁give ▁