A convex mirror always forms an image of a real object that is:

For a convex mirror the focus lies behind the mirror and reflected rays always diverge. Regardless of where the real object is placed, the rays only appear to meet behind the mirror, giving a virtual image. Geometric construction shows the image is always erect and smaller than the object. Convex mirrors are therefore used as rear-view mirrors, because they give a wide field of view with an upright image.