Maybe this is already well understood, but it is new to me and I thought I would share. I was trying to cull through a series of similar photos in a folder. I decided to set all files with a Rating of 3 and then as I viewed each file individually I would rate the image up or down from 3 as I decided whether the image was better or worse. I wanted to then filter on only images greater than 3. What I noticed was that the filter for Rating disappeared from the Filter palette/panel. After some fiddling and comparing with an older version of Bridge, I discovered that if all files in the folder have the same Rating value then the filter disappears, but once I change at least one file to have a different Rating value from the rest, then the Rating filter appears once more. Starnge but true (for me).