Camera / Perception Tutorials in ROS

Hello, I'm working with 2 robots, each one with one camera. I'm first simulating the robots. Are there any tutorials about Vision in ROS? Where you can learn the basics? I had courses in Image processing and Vision but I never worked with image/cameras with ROS. I'm doing the Visualisation tutorial but I think this is not what I want....Any recommendations? Thx you so much!