This lens was manufactured to be compatible with the 40mp sensor and should produce great optical quality. It's also a nice compact size. F3.5 seems like a reasonable compromise since you're not going to have much blurred backgrounds with such a wide follow length to start with.
Key specifications:
- APS-C sensor coverage
- 12mm in Full-Frame equivalent
- 215g
- Aspherical and low dispersion elements
- 62mm filter thread
- $800