Why does an imported photo on my computer screen in Library and Develop modes in LightRoom 3 appear to be less sharp than the original photo? What to do? When I export the same photo, without making any adjustments to the photo in LightRoom, it appears to be sharp again.
When importing, are you having LR build 1:1 previews? There is a setting in the import window under File Handling. For files already imported, in the Library module, select one or more photos then click Library > Previews > Build 1:1 Previews. (This is for LR5, but I LR3 is probably the same.)
Are you talking about the difference between the camera-jpg-preview that has some sharpening applied in-camera as compared to default processing in LR which doesn’t have that much sharpening, or are you saying the library and develop modes are very pixilated? Some screenshots of what you’re talking about would help understand.