Jae, that all makes sense - not sure what happened with my thinking - got caught in at least two minds + general brain fade I suspect.
Just a couple of points. 1) I wasn't trying to depict refraction - now that would be a step too far for my brain - simply the distance from the 'centre' of the lens to the edges of the sensor. 2) As long as the 'centre' of the lens is in front of the axis of rotation, then focal length isn't related to focus-shift, since the distance from the axis of tilt to the sensor plane is the same for whatever lens is stuck on the T/S adapter, and however much it is tilted. However this is only true of lenses in front of the axis of tilt, once the 'centre' of a lens is behind it (such as with some retrofocus lenses or lenses on recessed boards) then the value of 'actual distance' (and thus the degree of 'focus shift') will vary according to focal length. 3) Longer focal length lenses tend to require more tilt on certain occasions (e.g. landscape: foreground to background in focus) which means the 'actual distance' in your diagram tends to be greater with longer focal length lenses and thus the effect is greater, both of 'focus shift' and the appearance of the subject on the sensor, due to the divergence of the values e and f on my amended diagram.
Jim
Just a couple of points. 1) I wasn't trying to depict refraction - now that would be a step too far for my brain - simply the distance from the 'centre' of the lens to the edges of the sensor. 2) As long as the 'centre' of the lens is in front of the axis of rotation, then focal length isn't related to focus-shift, since the distance from the axis of tilt to the sensor plane is the same for whatever lens is stuck on the T/S adapter, and however much it is tilted. However this is only true of lenses in front of the axis of tilt, once the 'centre' of a lens is behind it (such as with some retrofocus lenses or lenses on recessed boards) then the value of 'actual distance' (and thus the degree of 'focus shift') will vary according to focal length. 3) Longer focal length lenses tend to require more tilt on certain occasions (e.g. landscape: foreground to background in focus) which means the 'actual distance' in your diagram tends to be greater with longer focal length lenses and thus the effect is greater, both of 'focus shift' and the appearance of the subject on the sensor, due to the divergence of the values e and f on my amended diagram.
Jim