 For ES-LV digicam users and ExpSim LV DSLR users, this advanced method of "Adjustable/Selectable Live Previewable Exposure Evaluation/Determination" shooting in Full Manual / M ISO mode completely eliminated light meter sensor reading TTL common from the film era, making optimally desired exposure selection with live preview rear monitor screens virtually "instant at a glance", and time was saved doing any spot/area evaluative light metering TTL, which non-ES-LV and totally non-LV DSLR users doing the TTL "light meter reading" routine, same as their film SLR counterparts.The time saved assessing instant optimal exposure choices for any new or changing lit scenario, freed the ExpSim LV DSLR users to spend all their time shooting primarily with their optical viewfinder (OVF).When interchangeable-lens DSLRs with STILLS only ExpSim LV (APS-C EOS 20Da, APS-H EOS 1DMkIII, Full Frame (FF) EOS 1DsMkIII), with its ExpSim LV having Full Manual / M/Auto-ISO mode and AE / M/Auto-ISO mode, ExpSim LV was extended for the first time in any interchangeable-lens DSLR to Canon's FF ExpSim LV (1080p) video in 5DMkIII, it was only then, did use of OVF shifted over, more to the rear lcd monitor to shoot Cinematic (larger FF sensor frame than pro digital Super35mm and 35mm Cine cameras).