Underwater Photography Judging Distance underwater. Parallaxing and refraction underwater is the biggest problem is to determine an estimated distance to establish the setting on the lens where a subject matter will be a sharp and chirsp image. In establishing a composition structure of taking picture, most key subjects will be at 2.5 feet to 4 feet of seen distance from the camera. However the refraction will result in a measured distance of 25% greater than perceived. This means learning to judge distance is very important for the settings, not a measurement.