Just recieved Rokkor 50/1.7 help needed with setings.

You can go fully manual, but I opt for auto ISO (in brightness/colour settings) on my NEX 5N.

That way you can control aperture, and shutter speed, while camera still works out exposure. Then use exposure compensation if you don't like what the camera chooses for you. Keep the histogram displayed to check for nice distribution and no highlight clipping.