Rebuilding the photos' small thumbnails seems to make the photos load much quicker, when double-clicked. And the image focusses quicker.
What additional advantages, if any, will the second option give - rebuilding all of the photos' thumbnails? I see that this can take some time to carry out.
I am not able to rebuild. I press the 2 buttons in sequence and nothing happens. I am using iPhoto 08. Will this affect?