In Studio Fix powder I use about a half shade lighter- NC35. It's mostly because my face and neck appears darker due to PX acne treatment irritation and my chest in actually lighter that NC35 ( more like a NC30! ) I wanted to make my chest, neck and face at least almost look the same. Otherwise it looks like I put on too much bronzer or forgot to put sunblock on some parts of my face. I also noticed when I used NC40 or C4 it did oxidize to a unnatural orange shade- not pretty.

I do think it's better to get something slightly lighter than too dark. But still get something in your skin tone/ color family.