Full Screen Preview (F) works incorrectly with selections when invoked from Grid view (G), though it does work correctly when invoked from Loupe view (E). Full Screen Preview should work just like Loupe view (and it does, when invoked from Loupe view).
1. Go to Grid view. Let’s call three consecutive pics A, B, and C.
2. Select A and B, with A most selected.
3. Go to Full Screen Preview; the most selected (A) is displayed.
4. Click right-arrow. Pic C is displayed, even though it wasn’t selected.
5. Go back to Grid view and notice the original selection has been lost; just C is selected.
With Loupe view, right- and left-arrow cycle among the selected photos, and the original selection is not changed (only the most selected). Full Screen Preview should work the same way. And if in the recipe above, after selecting A and B, if you first enter Loupe view and then Full Screen Preview, left- and right-arrow work correctly, cycling among the selected pics A and B.
See here for another Full Screen Preview bug dependent on whether it is invoked from Grid or Loupe view:
This is fixed in LR 6/LR CC 2015. But another bug was introduced -- flagging or rating a photo in Full Screen Preview now affects all the selected photos, rather than just the current one: http://feedback.photoshop.com/photosh...