You cannot open Raw files from the Samsung NX300 in CS5.
Camera Raw plug-in | Supported cameras
Camera Raw-compatible Adobe applications
You need Adobe Camera Raw 7.4 or later which is only compatible with CS6 or later.
Some choices:
- Upgrade to CS6
- Join the Cloud
- Join the CCPP
- Free option: download the free Adobe DNG converter, convert all Raw files from the NX300 to DNGs then edit the DNGs in CS5
Photoshop Help | Digital Negative (DNG)
