I didn't use a tilt-and-shift lens or apply any image warping to this photo. That said, I agree that it's challenging to be sure of the sense of scale in a photo like this as there aren't a lot of reference points. For example, it wasn't at all practical to have my partner stand near the falls (or for me to stand there while she snapped the picture). All you've got to go by are the size of the leaves on the trees. ...And some of those are a bit misleading as some of the trees are closer than the falls.