Photo wrong thumbnail In the Finder of my mac, it often happens that some photos in a folder are displaying wrong previews. The set of photos which have this problem is random and unpredictable: sometimes among 10 photos in a row there is one with a wrong thumbnail. The wrong thumbnail is always another photo in the same folder. Rebooting the machine does not help, which means the wrong information is stored somewhere. When I duplicate the photos (as an experiment), the new copy is OK.

I wonder if there is a way to force refreshing the thumbnails.

MacBook Air (13-inch, Early 2014), OS X Yosemite (10.10.2)

I have also asked this question on https://discussions.apple.com/thread/6988345 but received no answer yet.
A couple of things you can try:


Open the folder in Finder - click on the Actions button- select Show View Options - put a check next to Show icon preview. If it's checked, uncheck it, close the window, open it back up and check it again
Head for your home folder - Library / Preferences - move the com.apple.finder.plist file to the desktop - log out and back in. If this fixes it, you can delete the file. This is going to reset all your Finder preferences to default.
the thumbnails are stored in a folder called com.apple.QuickLook.thumbnailcache in a subfolder of /var/folders. The quickest way to locate it should be to run sudo find . -name com.apple.Q*. You could move that folder to a different location and restart the Finder process (killall Finder) to force a recreation of the thumbnails.