You need a much newer Mac to synch the phone. However, Image Capture may "see" the images on the phone.
EDIT: NOPE! No joy. I have an iPad running iOS 8.3 and just plugged it into my G4 MDD running 10.4.11 and the computer did not recognize the iPad; Image Capture reported "no devices detected" or something to that effect.
You might check in the iPhone forums to see if someone has a workabout. However, the bottom line is that a G4 "anything" is struggling today. The last ones were shipped 11 years ago. I keep mine set up to run an older version of creative suite, but that's about all it handles well any more.