Eric,
I got my flexible tape with adhesive back from a local store that specializes in woodworking shop tools. I believe you can get one at amazon.com. (See
http://www.amazon.com/Biesemeyer-79-...7?ie=UTF8&s=hi)
You could look in your phone book for a local store which has such a tape or can order one, or you can search the web for other sources.
The tape comes with English units on one side and metric units on the other, but it is not hard to cut it down the middle to produce a metric only scale that fits more easily on your camera.
Amazon also sells flexible fiberglass metric tapes which you could attach using double stick tape.
One thing you might also consider is adding an additional scale to your focusing knob. Because of the gearing, this may allow finer adjustments. See my article
http://www.math.northwestern.edu/~le.../dof_essay.pdf
for an explanation of how I did that for my Toho FC-45X.
As to your basic question, remember that the region in adequate focus is a wedge centered on the so-called hinge line. If you tilted the back, the hinge line would be in a plane parallel to the back and some distance below the lens. That distance depends on the tilt, being large for small tilts and getting smaller for larger tilts. The DOF region has small vertical extent close to the lens which increases linearly as you move further from the lens. As you focus, the whole wedge swivels on the hinge line. If the midground dips below the foreground and far distance, it would be easy for the midground to fall outside the wedge while the rest of the scene would remain in focus. You might be able to get in focus simply by rotating the wedge downward by refocusing, but in that case you would run the risk of moving the foreground or background out of the DOF wedge.
I've made some rough estimates from the data you gave. I think you would have to tilt something like 10 degrees or more to have any chance of getting the foreground in focus. But then at 15 feet the vertical extent in focus would only be about 1.6 feet. Depending on the topography, it might be very hard to get the dip in focus while still keeping both foreground and background in focus.
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