The technology relates to autonomous vehicles that use a perception system to detect objects and features in the vehicle's surroundings. A camera assembly having a ring-type structure is provided that gives the perception system an overall 360° field of view around the vehicle. Image sensors are arranged in camera modules around the assembly to provide a seamless panoramic field of view. One subsystem has multiple pairs of image sensors positioned to provide the overall 360° field of view, while another subsystem provides a set of image sensors generally facing toward the front of the vehicle to provide enhanced object identification. The camera assembly may be arranged in a housing located on top of the vehicle. The housing may include other sensors such as LIDAR and radar. The assembly includes a chassis and top and base plates, which may provide EMI protection from other sensors disposed in the housing.