Imagine the camera were floating just above the surface of the Earth, and also that it had perfect image stabilization. This image stabilization would keep the

Imagine the camera were floating just above the surface of the Earth, and also that it had perfect image stabilization. This image stabilization would keep the camera always oriented in the same direction. Same direction relative to what? To the rest of the universe. So if it was pointing right at a star, it would continue pointing directly at that star as it went around and around the Earth. From our perspective on the surface, the camera would appear to be flipping over itself as it kept pointing at that star. Unfortunately, this would be pretty bad for taking a picture of something that was right in front of the camera (relative to the surface of the Earth). You'd be in front of the camera, ready for your picture, and the camera would appear start rotating as it kept that distant star in view. So with a perfect image stabilizer, this is what the camera is actually trying to do, even when standing on the Earth with a tripod. It actually senses the rotation of the Earth, and tries to cancel it out, just like it would cancel out your hands shaking. But while it's good to cancel out your hands shaking (because that's a motion that's independent of the subject of the photo), it's not good to cancel out the rotation of the Earth (because the subject of the photo is actually moving with you).