Disabling camera for Facetime by default?

Is there a way to turn off the camera in FaceTime, by default? Is there a setting I've missed? (Yosemite, MacBook Pro)

I of course realize that the idea of FaceTime is being able to see the other person, but most of the time I'd prefer to answer or make a call without video.

(And yes... -Putting tape over the lens is an option, but not the solution I'd prefer.)

=)

Ole