Will I lose all existing photos if I turn on photo-syncing to iTunes for the first time? iPhone4, syncing to iTunes 10.6.3 on a mac G5 running OS 10.5.8
(This is the latest system version that the G5 will run)

I sync some audio on the G5 to my wife's iPhone, no problem.
About half the iPhone memory is taken up with photos going back several years- photos have never been synced. If I turn ON photo syncing now, will it delete all photos on the phone? We do NOT want this to happen! But it's clogged up, and the photos don't need to be on the phone, just kept somewhere else where we can see them. But how do we get them to that "safe somewhere else" without risking them getting deleted forever? [I really miss the days where an iPod showed up on the desktop as an external disk, and you knew where you were!!!!]
The dialogue on iTunes says 'Sync from folder...' which is what alarms me. I want things to go from the phone to a folder.

Hope someone can explain this to me. Cheers!
@IconDaemon is right, best bet is to use Image Capture to download the photos to your Mac:


Connect the phone via usb.
Spotlight "Image capture" or Go To... /Application/Image Capture
Under devices in the image capture window you should no see the
iPhone, select it and it will start loading all the photos.
At the bottom of the window there is a "Import to" selection menu. Choose an iPhotos library, or just select a folder to download to, then click import all


You can optionally choose to delete the photos from the iPhone once imported.

Now that the photos are on your Mac, you can turn on iTunes syncing for photos and select the iPhoto library or folder that you choose to download to.