Three Ravens or three crows

Yesterday I looked out a window to the north and there were 3 large black birds in the field just north of the trees. Ravens or crows? There are several differences between the two but the most noticeable is size. Crows average 17 inches and ravens 28 inches. These guys were big so I am thinking ravens but then they had a definite "caw, caw, caw" and I think the raven's voice is a low, slow croak.

I ran for the camera and snuck outside (in socks mind you) but they took flight as soon as they saw me. Another Kodak moment gone to the way side. Caw, caw