03-09-2016 04:04 PM - edited 03-09-2016 04:07 PM
I assumed the EF 100-400mm f/4.5-5.6L IS USM Lens, which has a MFD of 5.9 feet.
I changed the distance to 3 feet. That's pretty tight. His original shot looks a little grainy and soft to me. He should take a longer exposure at ISO-100 from a tripod.
[EDIT] At 25 feet, the DOF is 3.22 feet.