With LR5 64-bit, which is great overall, when I zoom to 1:1 in the develop module I get a sharp image within a fraction of a second, but when I then go to full screen, the full screen image is usually out of focus (not sharp), and stays out of focus unless, oddly, I use the arrow keys to advance to the next image in the film strip and then return, at which point it usually quickly regains sharp focus. The same thing usually happens when I go to full screen first and then zoom to 1:1. Sometimes, however, I do get a sharp full screen or full screen zoomed image immediately. I'm using a computer with 8 GB of RAM, and 8 logical processors, and it seems to handle everything else in LR5 with ease, including maintaining sharp focus (once I have it) when I drag a zoomed image to look at another part of it on my screen. Any idea what is going on, and how to fix it (other than just continuing to advance an image and return)?