uOpt wrote in post #16363719
Say I am standing 30 meters above ground with a 24mm shift lens. The shift angle I would need is 0.04583 degrees to put the Scheimpflug line on the ground. .
You are correct. When the focal plane (usually ground plane) is far from a wide angle camera lens, the amount of tilt angle (not shift angle) is negligible. If you take all of your landscapes at a high vantage points, there is no need of a tilt lens. However, as the camera nears the focal plane and the focus length of the lens increases, the tilt angle starts to increase in a very non linear fashion. This table lists the tilt angle as a function of lens focal length and distance of the focal plane from the lens center.
Note that using a Canon 17 TSE lens, very little tilt angle is needed until you get to about a lens height of about 2 feet (1.6 degrees). However, at 2 feet you have already exceeded the maximum tilt angle capability required for a Canon 90 TSE (8 degrees). Even with wide angle tilt shift lenses, as you get closer than 6-12 inches the amount of tilt required really climbs. At high tilt angle, fine adjusting lens focus and tilt angle can be very difficult, as these two variables interact. A good tripod permitting low angle camera positions, and careful adjustment of magnified Live View are essential. A very general rule of thumb is to use a near field object to fine adjust the tilt and a subject at infinity for focus. several iterations of focus and tilt angle adjustment are often required.
Here is an article with these calculations formatted in a lens specific fashion. The author suggests for a WA lens, standing height, that a tilt angle estimate via the table is sufficient. Don't bother with more tilt angle adjustments, simply focus and shoot. However as one kneels and gets lower, more care is needed in setting tilt angle.
If the low angle shot is not your compositional cup of tea, then perhaps you will only use shift, not tilt.