Sensor size doesn't really have an effect - it's about focal length. The reason sensor size seems to have an effect is because for the same field of view with

Sensor size doesn't really have an effect - it's about focal length. The reason sensor size seems to have an effect is because for the same field of view with a bigger sensor, you have a longer focal length. For the same focal length, aperture and focus distance, a larger sensor doesn't change DOF; it just adds more of the surroundings to the outside of the picture.