I recently exported a photo for a client from LR using my "FullRez jpeg" preset that does no resizing at all. It is a 3706x2520 file and it exported as a 2432x1634 file. Hmmm. Tried it again, this time as a "FullRez tiff". Same, smaller dimensions.
I double-checked the Develop module panel and below the histogram, sure enough, it said "Original File" and nothing else. The file info also showed 3706x2520 pixels. See attachment. What's up with this?
To have a look at the original file, to make sure all was well with it, I right-clicked to bring up the contextual menu and chose "Show in Finder". Lo and behold, LR tells me it can't find the original file. I plugged in my external drive and voilà - I can export using my "FullRez jpeg" preset perfectly well at the correct, full resolution dimensions.
So - why would LR tell me "Original File" under the histogram (NOT "Original File + Preview") then act as if it is using the larger, original file during export.
I would have thought there is some kind of a check mechanism so that if the original-sized original is not available, it would tell me during the export. It's nice that LR can export files from the JPEG preview when it is smaller than the Preview, but it should somehow indicate that it's not creating the file from the original, but from the preview, especially when in Develop module, it does not indicate anything other than "Original File".