On my OS X Yosemite (10.10.3) LR 2015 is set up not to import duplicates. Now each time I insert an SD card with a growing number of pictures on it, LR shows and preselects all of them to be imported. I have to deselect all and then manually select only the new ones - very annoying.
I rename pictures on import, this could be the reason. If this is the case, then it is a silly one - the original file name should be contained in EXIF, I think. So LR should be able to recognize duplicates. I used same preferences in Aperture previously and never had problems with it - Aperture seems to recognize already imported pictures good enough.
Does it have to do with my renaming pictures on import? Or do I miss something?