I don't shoot a lot of portraits, but when I do, I use a 35mm or my RB67. I see a lot of portraits on this site with very shallow DOF. I don't understand how you maintain the subject in the precise position to keep the focus around their eyes. Do you watch the ground glass carefully, then when you have everything lined up, slap the film holder in, yank the darkslide, and hit the cable release? I don't see how you could work with the subject that way, so if you pre-focus the camera, and leave a film holder in and darkslide pulled, then I just don't see how you can keep the subject in the plane of focus when DOF is only a few centimeters. It seems like it would be much easier with an SLR, but few people seem to use large-format SLRs.