Sat 01-Dec-12 02:59 PM | edited Sat 01-Dec-12 03:04 PM by Chris Platt
30ft with a 400mm lens should get you accuracy within that 1 foot range. My tests suggest that the reported distance for fairly close objects is quite accurate. 30 ft at 400 mm is very close. I just tried it with a 400mm setting, measuring a 29' 9" distance from the focal plane to a target with a tape measure. I tested with aperture settings from f5.6 to f32 giving DOFs that ranged from about 1/3 foot to 2 feet. I then tested at 100mm from f5 to f25 giving a DOF range from 3 feet to 35 feet. In every shot the exif reported 29 feet. If your target is beyond the hyperfocal distance the focus distance reported won't be the camera to subject distance, but probably something very close to the hyper focal distance (the near limit of the infinite DOF).