▁ 1 3 5 ▁film ▁image . ▁Most ▁A PS ▁cam eras ▁( with ▁the ▁exception ▁of ▁some ▁dispos able ▁cam eras ) ▁can ▁record ▁all ▁three ▁formats ; ▁the ▁format ▁selection ▁is ▁indicated ▁on ▁the ▁film ▁by ▁a ▁series ▁of ▁exposed ▁squares ▁alongside ▁the ▁image ▁area ▁or ▁recorded ▁on ▁the ▁magnetic ▁co ating ▁depending ▁on ▁the ▁camera . ▁In ▁the ▁absence ▁of ▁an ▁operator - spec ified ▁format , ▁the ▁machine ▁printing ▁an ▁A PS ▁roll ▁will ▁use ▁these ▁indic ators ▁to ▁determine ▁the ▁output ▁format ▁of ▁each ▁print . ▁ ▁Film ▁and ▁cart ridge ▁▁ ▁The ▁film ▁is ▁on ▁a ▁poly eth yl ene ▁nap h th al ate ▁( P EN ) ▁base , ▁and ▁is ▁hous ed ▁in ▁a ▁single - sp ool ▁ 3 9   mm ▁long ▁pl astic ▁cart ridge . ▁The ▁basic ▁diameter ▁is ▁ 2 1   mm , ▁while ▁it ▁measures ▁ 3 0   mm ▁at ▁the ▁slot ▁where ▁the ▁film ▁ex its . ▁The ▁slot ▁is ▁protected ▁by ▁a ▁light proof ▁door . ▁It ▁is ▁available ▁in ▁ 4 0 , ▁ 2 5 ▁and ▁ 1 5 ▁expos ure ▁lengths . ▁The ▁film ▁surface ▁has ▁a ▁transparent ▁magnetic ▁co ating , ▁and ▁the ▁camera ▁uses ▁this ▁information ▁exchange ▁( IX ) ▁system ▁for ▁recording ▁information ▁about ▁each ▁expos ure . ▁The ▁camera ▁handles ▁w inding ▁and ▁re w inding ▁automatically , ▁to ▁the ▁extent ▁that ▁partially ▁exposed ▁films ▁can , ▁in ▁certain ▁cam eras , ▁be ▁removed ▁and ▁used ▁later