Alan,
I think you are confusing applying tilts/swings (i.e., positioning the plane of sharp focus) with determining the optimum f-stop from near and far points that you want to be in sharp focus.
Yes, you need focus points to apply your tilts and swings too, but they are not the same ones
Applying tilts/swings is a different thing than finding a focus spread in order to determining the optimum f-stop.
With asymmetrical movements, one of the focus points is always on the axis line, which you focus on with the main focusing (i.e., bellows extension) The other point is one you choose on the opposite side to swing/tilt into focus. This is how you get near/far or right/left objects in the same plane of focus. However, this isn't finding the focus extremes to determine your f-stop.
Once you have applied your movements, THEN you look for objects that are outside the plane of sharp focus. You want to choose the nearest and the farthest point from that plane that you want in sharp focus. THESE are your focus points for finding the optimum f-stop. You focus on one extreme, note the position of the standards on the rail/camera body, then focus on the other extreme and note that position. The distance between the two extremes (the focus spread) will tell you what your optimum f-stop should be (having a mm scale or ruler on your camera helps a lot to determine this. All my cameras have mm scales taped on.)
For the final shot, you focus, i.e., position the standards, exactly halfway between the two extremes on the rail/camera body (NOT focus on an object halfway between those extremes in the scene! - Just pay attention to the actual physical distance between standards).
If you read the article on determining the optimum f-stop that I linked to above, you will find everything you need to know about which f-stop to choose for whatever focus spread you have.
What I was trying to point out to Creation Bear above is that when you apply, say, a lot of tilt, the plane of sharp focus can be horizontal in the scene. In that case, "nearer" objects are above the plane of sharp focus and "farther" ones are below the plane of sharp focus. So, if you have this configuration, the "nearest" object would be the one that is closest to the camera and above the plane of sharp focus (this could be a flower sticking up from the foreground). The "farthest" would be the one below the plane of sharp focus farthest from the camera (this could be the base of a mountain where it meets the plain if you've positioned your plane of sharp focus halfway up the mountainside. - Note that the peak of the mountain would then be above the plane of sharp focus and actually "closer" to the camera optically!).
Hope that clears things up.
Doremus
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