ShiftN 2.2
ericN2

If you are a user of any sort of Wide-angle lens , or indeed just using a normal lens at wde aperture , then you will without doubt have had the inevitable convergence or proportional distortion that can spoil a good pic. No prog will work miracles in such cases, and indeed there are one or two other programs that include some adjustment for this - but Shift-N is just for this alone, is very easy to work with , and in fact in the situations where it does give the desired result , it is literally just a two-click program.
It really does the job in so many cases, to effectively make a picture that much better.
Heartily recommended.