I'm using SharpDX on the Windows Phone 8 and therefore although it uses DirectX11 it is feature level 9_3. This means certain things won't work on the device but will work on the emulator. I have a shader working on the emulator that uses alpha blending but I can't get it working on the phone at all. Basically I am drawing to a render target without clearing it and then drawing that to another one and multiplying the alpha by 0.95 to slowly fade it out over time. On the emulator this creates a nice fading trail behind a moving object. On the phone however the trail is just always the same colour and doesn't fade.
I am assuming this has something to do with feature level 9_3 but I can't figure out what it is I am doing that is wrong.