This conversation has been merged. Please reference the main conversation: Lightroom: Invalid constraint size error
When I select "long side" in sizing options, enter the size in cm or inch and enter 600dpi Lightroom will immediately show an error message like:
"The dpi is too high, it needs to be in the range of 1 to 275"
and sets the dpi to 275.
Higher values will produce different max for the error, but do not work, either.
I can work around this problem by selecting "width by height" or enter the pixel count instead of the cm/inch-size. But this is annoying since I use this kind of export a lot.