I have OS 10.9.5 with iPhoto 9.5.1 and iPhoto will not accept my raw files from my Nikon D750. Is there an upgrade to accept my new camera?

on 18 aug there was a new update of cameraraw (appstore). see if your camera is in there

Open the App Store and check for updates. There have several RAW updates over the past few months so see if you are missing any. I don't remember one that specifically said the 750, but look and see what you may have missed.

The compatibility updates for the Nikon D570 require the 6.0.1 updater which in turn requires Yosemite and iPhoto 9.6.1.

You'll need to upgrade to Yosemite or convert the RAW to .dmg files with Adobe's RAW converter application and use .dmg files.

In addition to OTs remarks, see OS X Mavericks: Supported digital camera RAW formats - Apple Support dated June 2015 which includes the D810 but not the D750.

Typo: .DMG files: you meant .DNG files.

best

Lex

Yup. DNG files Thanks for the typo catch.

I have all raw files in my computer converted to DNG: a more standard "standard" than the camera raws. And the advantage is also that the DNG files are smaller.