Image-based visual servoing has been found generally satisfactory and robust in the presence of camera and hand-eye calibration errors. However, in some cases, singularities and local minima may arise. We propose a modification of the feature vector which alleviates this problem without need of introducing further information, i.e., only pixel coordinates and depth estimations are used. Using the task-function approach, we demonstrate the relationship between the velocity screw of the camera and the current and desired p oses of the object in the camera frame. Experimental results on a real robotic platform illustrate the presented approaches.