MO ▁offered ▁a ▁novel ▁and ▁rare ▁ 1 0 0 - foot ▁magazine . ▁The ▁ 1 0 0 - foot ▁mag ▁was ▁the ▁height ▁of ▁the ▁camera , ▁so ▁the ▁camera ▁with ▁mag ▁would ▁be ▁only ▁ 5   in ches ▁tall . ▁The ▁G S MO ▁did ▁not ▁have ▁video ▁assist , ▁a ▁way ▁of ▁view ing ▁what ▁the ▁cam er aman ▁was ▁seeing ▁on ▁a ▁video ▁screen . ▁TV ▁commercial ▁produ cers ▁and ▁direct ors ▁wanted ▁video ▁assist , ▁and ▁the ▁G S MO ▁fell ▁behind ▁the ▁competition ▁in ▁that ▁feature . ▁( After - market ▁video ▁assist ▁is ▁now ▁available ▁for ▁the ▁G S MO ). ▁ ▁- ▁ ▁R are ▁l ens ▁During ▁pre - production ▁for ▁the ▁ 1 9 7 5 ▁film ▁" Bar ry ▁Ly nd on ", ▁director - produ cer ▁Stanley ▁Kub rick ▁had ▁a ▁requirement ▁for ▁a ▁large ▁a pert ure ▁" high ▁speed " ▁c ine ▁l ens ▁to ▁facil itate ▁shooting ▁scenes ▁by ▁cand le light . ▁At ▁the ▁time , ▁the ▁largest ▁a pert ure ▁" fast est " ▁c ine ▁l enses ▁available ▁for ▁ref lex ▁ 3 5 mm ▁c ine ▁cam eras ▁had ▁a ▁f 1 . 4 ▁a pert ure . ▁High ▁Speed ▁( also ▁called ▁" Super ▁Speed ") ▁f 1 . 2 ▁prime ▁l enses ▁were ▁not ▁available ▁at ▁the ▁time . ▁ ▁Kub rick ▁s our ced ▁a ▁Carl ▁Ze iss ▁Plan ar ▁f 0 . 7 / 5 0 mm ▁l