National Geographic : 1953 Oct
Tex Helm Mounts His Camera Ladders to Shoot the Cave For his color pictures of Carlsbad Caverns, Mr. Helm never set up fewer than a (lozen cameras, each with a different lens opening to vary the ex posure. He opened and closed shutters in total darkness, al lowing flashbulbs to make a 1!30-second time exposure (page 448). "As the caverns' floodlight ing is dim," Mr. Helm points out, "visitors are only throw ing their money away trying to make movies and color stills. The only effective method is flash." -< -Mr. Helm stands behind 2,400 spent bulbs used to illu minate the Big Room (page 464). These and others were provided by Sylvania Electric Products as an experiment in lighting vast sunless areas. Each bulb produced as much light as 1,290 sixty-watt house lamps.