I'm using Vuforia 4.103 with Unity 4.6, and I'm having the same problem using both my app and the Vuforia Target sample, doing tests with a Nexus 7 and a Nexus 5, both with latest Android 5.0.
Problems are: image quality, image viewport, image darkness (of vuforia preview compared to camera app preview)
I've made a collage of 4 screenshots: Nexus 7 and Nexus 5 vuforia preview, Nexus 7 and Nexus 5 camera app preview.
With Nexus 7, the camera preview quality is much lower then the standard camera app (seems half resolution). Changing camera mode quality (quality/speed) doesn't change anything.
Tried with my app (return value of the operation true) and with the Vuforia sample.
With Nexus 5 quality appears to be the same. Even there, chenging camera mode from speed to quality doesn't change the quality (what is supposed to change? resolution?).
Another problem is that the viewport is different, the camera preview with the camera app is wider.
Third, smaller problem, vuforia camera preview is darker. You can notice a little in this comparison but I had cases when there's a huge difference (I just close the vuforia app and go to stock camera, with same lighting conditions, and preview is much less dark).
Is there any way to solve this problems, on my side I mean?