Time machine backups and deleted files If I delete photos from my current iPhoto library which have been backed up on time machine, will it be possible to recover these photos from my time machine backup once they've been deleted from my hard disk/iPhoto library? or will time machine eventually delete them next time I backup?  does time machine keep my backups for a particular period of time before deleting them to make room for the next round of backups?
By default, Time Machine keeps the following backups:


Hourly for the current day
Daily for the past month
Weekly for all the other months


If there's space constraints then Time Machine will start to delete the backups, but otherwise it keeps them for as long as possible.

To get to the individual photos you will have to have iPhoto as the active window when you activate Time Machine from the menu bar. This lets you go back and see all of the photos. If you did it from the Finder it's more complex because iPhoto bundles its whole library into one big package.