chrisd999 wrote in post #15483655
So based on this, I take it you are saying that using tilt with the 17mm TS lens will increase the DOF versus no tilt, but you need to still follow good focus placement to get all sharp and in focus?
Tilt does NOT affect DOF deepness, per se!!! The DOF zone is always a given amount, tilted or untilted. The use of tilt simply moves the plane of focus so that it is the better aligned to the plane of primary subject interest (the ground, in this case).
Here is the principle illustrated...
The darker arrow is in focus with normal lens angle, but the light blue arrow is outside the vertical DOF zone from the primary plane of focus (at the dark blue arrow).
By tilting the lens, the plane of focus moves to an angle so that some
of the light blue arrow is in focus, but the TOP of the light blue arrow and some of the BOTTOM of the light blue arrow is still outside
the tilted DOF zone. And note that the TOP of the dark arrow is now out of focus as well, with only the bottom of the dark blue arrow staying inside the tilted DOF zone! Imagine shooting a shot with tall redwood tree in foreground as well as in background, and the tops of the trees are not in focus as a result.
The depth of the DOF zone is greater with the smaller (APS-C) format than with large format, so you would not encounter as frequently the issue experienced with larger formats, that the entire dark blue arrow is no longer in focus.