Fonts look not contrast and blurry

Fonts in my application look not very contrast and some what blurry. Especially when the color is white and there is a background image.

I use Helvetica Neue, sans-serif.

I used Nexus 5 to compare the look and feel of my application with other apps. Other apps look much more contrast on the same device. So, it’s not the device.

Does anybody encountered similar problem? Any idea how to improve it?