In the case of smooth pursuit, the eye slowly rotates to track a moving target feature. Examples are a car, a tennis ball, or a person walking by. The rate of rotation is usually less than 30 per second, which is much slower than for saccades. The main function of smooth pursuit is to reduce motion blur on the retina; this is also known as image stabilization. The blur is due to the slow response time of photoreceptors, as discussed in Section 5.1. If the target is moving too fast, then saccades may be intermittently inserted into the pursuit motions to catch up to it.