I photographed this on a recent trip to Texas. One of my must have shots was here at the Hamilton pool outside of Austin. I used a 9 stop ND filter to smooth out the water and let the people in the frame fade away. I shot on my Manfrotto 055CXPRO3 tripod with a Canon 16-35 f4 at 16mm on a 6d body. Aperature priority set to f13 ISO 400. I shot with a 3 stop bracket set 2 stops apart to blend the two extreme lighting for the cave and the sky. Or course being an HDR and shot in raw I had to do some processing in Lightroom to blend the images and bring back some detail in the shadows and highlight.