Last weekend, I had my first experience in a studio sighting. All kinds of lights, including boxes, huge portraits, over head, and large ring lighting. Its a whole new world of photography with models in a studio. But my question, this was a workshop and the instructor instructed us to set our cameras at 1/250 f/8 and ISO 100 for the shots as it would ensure everything was in focus and no bokeh affects. How did he know this? We were all Canon thus the ISO, but why f/8 when you have the best lighting available? I've heard "just f/8", but why 8?