Hay Albert:

I'm with Dan on this one. I've read Merklinger's book "Focusing The View Camera" and he is right on the money with his theory. However, it is kind of difficult to apply in the field. It still seems to me that the photographer must know, before hand, both the vertical and horizontal distances to the principal objects in the scene that determine the principal plane of focus. I might be wrong here, if I am, please correct me.

So I look at the scean and visualize where I want the plane of sharp focus to be. I focus on the foreground, then tilt, then re-focus on the foreground. Then I examine the ground glass to see if my background object is also in focus. If not, I tilt one of the standards accordingly. Then I start over. The process continues until my plane of sharp focus cuts the foreground and the background where I want it to.

The trick is having an understanding of where the depth of field planes go as the standards are tilted. Merklinger does a fantastic job of describing this, but, I think an intuitive understanding or 'feel' for it is sufficient. At least for me anyway.

I hope this adds something to the discussion.

Regards,

Jason.