Question about prime lens distortion and DX sensor....

if the frame size is smaller, the percentage should go up, not down.

check out the reviews for the lens in question:

http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/209-nikkor-af-20mm-f28-d-review--test-report?start=1

http://www.photozone.de/nikon_ff/617-nikkorafd2028ff?start=1

DX: -2.29%

FX: -2.26%

probably not statistically significant, right? personally, using the manual version of this lens, i found the distortion easier to live with on FX than on DX. but that's just my subjective assessment.