This advanced exposure simulation live (pre-)view ES-LV on Canon's prosumer Powershots was absent on all interchangeable-lens DSLRs till Canon introduced a first ES-LV for an interchangeable-lens DSLR (they dubbed it: "ExpSim LV" version) in its EOS 20Da, to preview star exposures live, which was similar to ES-LV found in its advanced prosumer Powershot digicams. Later, Canon extended its more sophisticated DSLR ExpSim LV all shooting light conditions like its Powershot digicams. The most significant advances and difference in DSLR version of ES-LV was simulating exposure changes effects with chosen aperture changes without stopping down the aperture. The ES-LV of its Powershot digicams always kept its apertures stopped down, so no 'aperture exposure simulation' was needed, and briefly opened aperture to assess focus with shutter button partially depressed before a shot is taken. The ExpSim LV of its EOS lens DSLRs could achieve the same 'exposure simulation' effect in both aperture stop-down mode and aperture wide open of its EOS lenses, even if the aperture selection was narrower than widest diameter (wide open).