PowerBook G4 17-inch won't recognize iPhone 4S

I have a PowerBook G4 17-inch that was made in 2004, its OS is Mac OS X Version 10.5.8. My phone is an iPhone 4S, it is updated to the latest version, iOS 8.4.1. I connected my phone to my computer and it will only recognize it as an iPhoto camera. iTunes recognized it initially, asked me to unlock my phone and asked me if I could trust the computer. I pressed yes, then it popped up with a window on the computer saying something about Quicktime not being up to date, but when I checked for updates, it said everything was up to date. The computer itself does not recognize my phone, I looked in Finder under devices and it does not show up, only in iPhoto does my phone even register on this computer. When I plug it into my iMac, however, or any other computer, it immediately recognizes my phone.

Is this happening because the computer is so old and cannot update to the latest software, and that's why it doesn't recognize my phone? Or is there some other problem? Any help is greatly appreciated.

Thanks!