I’ve discovered how to achieve that super-duper narrow depth of field like you get with medium format (the Martin Schoeller look) without having to buy an 85mm f1.2 or use a Mamiya 6×9 camera …. the secret … use a macro extension tube!
The 85mm f1.8 only focuses close enough to do a head and shoulders… put a short 12mm extension tube on the lens and I am able to almost completely fill the frame on a full-frame Canon 5D camera.
Since DOF is controlled by three things: F-stop, focal length, and distance to subject…. the extension tube allows me to get even closer to the subject = super narrow depth of field. Your focus has to be EXACT though or else you ruin the photo.