Thanks for Your comment, Mr MediumFormatMan :) It was taken handheld, so exposure was set to achieve ≥ 1/20 sec. There wasn't any space to move. Wide open aperture (f2.8), sensitivity was set to upper minimal value, which compensates lack of light. I shot it in Aperture-priority mode, so I had lowered about 1/3 EV to central-weighted indication of light-meter.