In Bridge you can enhance imported thumbnail images to a high quality, however in Lightroom 3 or 4 this does not appear to be the case, with images appearing of a lesser quality. Is there a process in Lightroom which will enhance thumbnail images to a high quality as in Bridge.?
are you seeing any quality issue or are you just asking because the option is not in LR?
i ask because i have not seen any problem with LR thumbnails looking bad.
i set my standard preview size to 1440pixel and the previews look fine.
when i get my 30" TFT some day i will up the standard preview to 2048 pixel.