Syncing iPhone

When I sync my iPhone with my computer, every single time, it is copying all the photos from my computer to my iphone, even though previously they have been synced and only a few were added to my iPhoto library. Since I have over 3,000 photos, the syncing process can take a long time. Why does it do this??

Syncing is the only way I can get my calendars and contacts to match up. Is there an easier way???