If you are having problems transferring photos from OS X Photos or iPhoto to your iOS device via iTunes you may need to clear your iOS Photo Cache.
Problems with this cache cause the wrong photos to transfer, or to not transfer at all. It can also cause iTunes to report incorrect information about what photos are on your device and how much space they are taking up. The solution is to remove it so it can be regenerated. Note this will probably remove previously transferred photos from your iOS device when you next sync (photos taken with the device won’t be affected). Always have an up to date backup!
How to clear your iOS Photo Cache
- Shut down iTunes and Photos / iPhoto.
- Find your Photos / iPhoto Library. It is probably in ‘Pictures’ in your home folder.
- Right click (or control-click) the Library and click ‘Show Package Contents’.
- In the folder that opens, find iOS Photo Cache and delete it. Do not delete anything else; you might corrupt your photo library.
Once you’ve done this, when you reopen iTunes and connect your device it will think Photo syncing is disabled, re-enable it and choose what photos to sync, and all should be well.