Originally posted by Nicolas06 You mean keeping the tree entirely in the picture or there any hard limit?
When the LR "distortion" slider is moved off center, it causes either barrel or pincushion distortion. To eliminate FE distortion, of course you move it to cause pincushion. When you crop to eliminate the lost areas, it is entirely the corners. The center left-right and center top-bottom of the image are preserved.Maybe I can post three images to demonstrate.
Below:
1) the first image has no distortion removed, but I've opened the shadows some and tweaked the colors to my taste;
2) the second image is the maximum pincushion distortion that the LR slider can apply
3) the third image is a crop of the second.
Differences are subtle. A telephone pole at left still leans, but it isn't as curved as in the original. More iteresting a valuable, the beautiful tree at left is now wider than in the original. The corners that have been lost do not contain visual information that contributes significantly to the image.