Imaging of three-dimensional objects by lenses and mirrors is sometimes poorly indicated in textbooks and can be incorrectly drawn. We stress a need to clarify the concept of longitudinal magnification, with simulated images illustrating distortions introduced along the optical axis. We consider all possible positions of the object for both a convergent and a divergent lens, producing real and virtual images. We also discuss spherical mirrors, elementary telescopes and microscopes. (Contains 6 figures.)